CN112664206B - Milling and excavating method for soft and weak cladding shallow-buried large-section tunnel - Google Patents

Abstract

The invention discloses a method for milling and excavating a shallow-buried large-section tunnel with soft and weak cladding, which comprises the following steps: S1, performing advance support on a rock mass on the right side wall of the upper pilot pit; S2, the right side of the upper pilot pit Excavate the rock mass of the first part of the wall, and implement initial support I on the right side, and temporarily support the middle wall of section A on the left side, and perform advanced support; S3, the second part of the right wall of the lower pilot pit The middle wall of section B is temporarily supported for excavation; S4, three rock masses on the right side wall of the lower pilot pit and four rock masses on the right side wall of the lower pilot pit are excavated, and initial support II is applied; S5, Apply advanced support to the five rock masses on the left side wall of the upper pilot pit; S6, excavate the five rock masses on the left side wall of the upper pilot pit, and apply initial support III to the left side, and perform advanced support; S7 , Excavate six rock masses on the left side wall of the lower pilot pit, and apply initial support IV to the left side; S8, excavate seven rock masses on the left side wall of the lower pilot pit, and apply initial support V to the lower side; S9. Remove temporary steel frames and temporary supports, and pour inverted arches and secondary linings.

Description

Excavation method of milling and excavation for shallow-buried large-section tunnel with weak cladding

technical field

The invention relates to the technical field of tunnel engineering, in particular to a method for milling and excavating shallow-buried large-section tunnels with weak cladding.

Background technique

In recent years, cross-river tunnels have developed rapidly at home and abroad. Due to the limited width of the crossing river, and considering the saving of urban land resources, the convenience of connecting the existing roads on both sides of the river and effective waterproofing, it is necessary to adopt the form of a shallow buried tunnel with a small clear distance. Commonly used construction methods for river crossing tunnels include shield tunneling method, immersed tube method, and mining method. Considering the short mileage of the river crossing tunnel, shield tunneling method is uneconomical; and immersed tube method affects shipping and is greatly affected by seasons, so the mining method is adopted Excavation is more environmentally friendly and economical. Small clear distance river crossing tunnels generally have the following characteristics: (1) The thickness of the covering layer on the top of the underwater tunnel is small; (2) The grade of the surrounding rock is poor; (3) The formation is rich in water; (4) The clear distance of the tunnel is small. Excavation by traditional mining method greatly disturbs the surrounding rock, which is not conducive to the excavation of underwater soft ground tunnels, while excavation by milling excavator will greatly reduce the disturbance to surrounding rock, which is suitable for the excavation of such tunnels . However, excavation by milling excavators is very different from excavation by traditional mining methods, and there is currently no construction method specifically aimed at excavating tunnels with milling excavators.

Contents of the invention

The invention provides a milling and excavation method for shallow-buried large-section tunnels with weak cladding to solve the problem that traditional construction methods are not suitable for shallow-buried small-space tunnels, and disturbance effects are likely to occur during tunnel excavation, causing surrounding rock Deformation, technical problems that cannot guarantee construction safety.

The technical scheme that the present invention adopts is as follows:

A milling and excavation method for shallow-buried large-section tunnels with weak cladding. The tunnel cross-section is divided into a right pilot pit and a left pilot pit by using the temporary support of the middle wall. The temporary support of the middle wall includes the temporary support of the middle wall of the upper section A The protection and the temporary support of the middle wall of section B at the lower part divide the right pilot pit into a rock mass on the right side wall of the upper pilot pit and a rock mass on the right side wall of the lower pilot pit according to the vertical direction, and the rock mass on the right side wall of the lower pilot pit From left to right, it includes two rock masses on the right side wall of the lower pilot pit, three rock masses on the right side wall of the lower pilot pit, and four rock masses on the right side wall of the lower pilot pit. The left pilot pit is divided into the left side of the upper pilot pit The rock mass of the fifth part of the wall and the rock mass of the left wall of the lower pilot pit, the rock mass of the left wall of the lower pilot pit from left to right in the horizontal direction includes the six rock masses of the left side wall of the lower pilot pit and the seven rock masses of the left wall of the lower pilot pit , including the following steps:

S1. Provide advanced support to a part of the rock mass on the right side wall of the upper pilot pit;

S2. Excavate a part of the rock mass on the right side wall of the upper pilot pit, and implement initial support I on the right side of a part of the rock mass on the right side wall of the upper pilot pit, and implement support on the left side of a part of the rock mass on the right side wall of the upper pilot pit The middle wall of section A is temporarily supported, and advanced support is applied to the rock mass of the second part of the right wall of the lower pilot pit, the third rock mass of the right side wall of the lower pilot pit, and the four rock masses of the right wall of the lower pilot pit;

S3. Excavate the rock mass of the second part of the right side wall of the lower pilot pit, and temporarily support the middle wall of section B on the second rock mass of the right side wall of the lower pilot pit;

S4. Excavate three rock masses on the right side wall of the lower pilot pit and four rock masses on the right side wall of the lower pilot pit, implement initial support II, and complete the initial support closure of the right pilot pit side wall to form a ring;

S5, perform advanced support on the five rock masses on the left side wall of the upper pilot pit;

S6. Excavation of five rock masses on the left side wall of the upper pilot pit, and initial support III on the left side of the five rock masses on the left side wall of the upper pilot pit, and six rock masses on the left side wall of the lower pilot pit and the lower pilot pit The seven parts of the rock mass on the left side wall are used as advance support;

S7. Excavate six rock masses on the left side wall of the lower pilot pit, and implement initial support IV on the left side of the six rock masses on the left side wall of the lower pilot pit;

S8. Excavate the seven parts of the rock mass on the left side wall of the lower pilot pit, apply initial support V to the lower side of the seven rock masses on the left side wall of the lower pilot pit, and complete the initial support closure of the left pilot pit side wall to form a ring;

S9. There should be an excavation footage distance between the left and right sides of the cycle step S1, with a difference of at least one. S8, until all the excavation is completed, the temporary steel frame and temporary support are removed, and the inverted arch and secondary lining are poured.

Furthermore, except that the two rock masses on the right side wall of the lower pilot pit were excavated by excavators, the others were excavated by milling excavators.

Further, the excavation footage of a part of the rock mass on the right side wall of the upper pilot pit is one block, and a part of the rock mass on the right side wall of the upper pilot pit is excavated for two blocks and then transferred to the second part of the rock mass on the right side wall of the lower pilot pit for excavation. , the excavation footage is two blocks, the middle wall of section B is temporarily supported, backfilled with gravel, and then transferred to the three rock masses on the right side wall of the lower pilot pit and the four rock masses on the right side wall of the lower pilot pit for excavation. The footage is two blocks, initial support II is applied, and gravel is backfilled.

Further, the specific steps for excavating the three rock masses on the right side wall of the lower pilot pit and the four rock masses on the right side wall of the lower pilot pit include:

S41. Excavate the four rock masses on the right side wall of the lower pilot pit, apply initial support to the right side of the four rock masses on the right side wall of the lower pilot pit, and backfill gravel;

S42. Excavate the three rock masses on the right side wall of the lower pilot pit, apply initial support to the lower side of the three rock masses on the right side wall of the lower pilot pit, and backfill with gravel.

Further, the distance L5 in the depth direction between the excavation surface of the second rock mass on the right side wall of the lower pilot pit and the top of the excavation surface of the third rock mass on the right side wall of the lower pilot pit is 1m to 1.5m; the height of backfilling gravel is ≥0.7 m.

Further, the excavation surfaces of the three rock masses on the right side wall of the lower pilot pit are inclined slopes, and the inclination angle i1 of the excavation surfaces of the three rock masses on the right side wall of the lower pilot pit is ≤ 16°; and/or, the right side of the pilot pit The lateral width L1 of the rock mass at the three parts of the side wall is 3.2m to 4m.

Further, the distance L3 in the depth direction between the excavation surface of a rock mass on the right side wall of the upper pilot pit and the excavation surface of the second rock mass on the right wall of the lower pilot pit is 16m to 20m; and/or, the right side of the pilot pit The distance L4 in the depth direction between the excavation surface of the four rock masses on the wall and the top of the excavation surface of the three rock masses on the right side wall of the lower pilot pit is 18m to 22m.

Further, the excavation footage of the five rock masses on the left side wall of the upper pilot pit is one block, and the five rock masses on the left side wall of the upper pilot pit are excavated for two blocks and then transferred to the six rock masses on the left side wall of the lower pilot pit for excavation. The excavation footage is two blocks, the initial support IV is applied, and gravel is backfilled, and then transferred to the rock mass on the left side wall of the lower pilot pit for excavation. stone.

Further, the excavation surface of the seven rock masses on the left side wall of the lower pilot pit is an inclined slope, and the inclination angle i2 of the excavation surface of the seven rock masses on the left side wall of the lower pilot pit is ≤ 16°; and/or, the left side of the pilot pit The lateral width L2 of the rock mass at the 7 parts of the side wall is 3.2m-5m.

Further, the distance L7 in the depth direction between the excavation surface of the five rock masses on the left side wall of the upper pilot pit and the top of the excavation surface of the seven rock masses on the left side wall of the lower pilot pit is 16m to 20m; and/or, the left side of the pilot pit The distance L8 in the depth direction between the excavation surface of the six rock masses on the side wall and the top of the excavation surface of the seven rock masses on the left side wall of the lower pilot pit is 18m-22m.

Further, advance support adopts advanced small conduit grouting and pipe shed, the grouting small conduit L is 3m-4.5m, and the pipe shed L is 3m-6m; initial support I, initial support III, initial support IV, The initial support V and the initial support II adopt steel arch frame, shotcrete and mortar anchor, and the mortar anchor L is 3.5m~4.5m; the temporary support of the middle wall adopts temporary steel arch frame, steel mesh, shotcrete, The leading small conduit and mortar bolt, the L of the small leading conduit is 3m to 4.5m, and the L of the mortar bolt is 3.5m to 4.5m.

Further, the safety distance L6 in the depth direction between the right pilot pit and the left pilot pit is 3m~5m; the depthwise distance L10 between the construction site of the inverted arch and the excavation surface of the six rock masses on the left side wall of the lower pilot pit is 16m~18m; The depthwise distance L11 between the lining construction site and the inverted arch construction site is 8m to 12m.

The present invention has the following beneficial effects:

The milling and excavation method of the shallow-buried large-section tunnel with soft and weak cladding of the present invention proposes a tunnel excavation method suitable for small clear distance, large section or super large section, poor surrounding rock conditions and extremely high requirements for surrounding rock deformation control , combined with the construction technology of CD method, CRD method and double-side-wall pilot pit method, and improved on the basis of CD method, the tunnel section is decomposed into 7 construction parts, and they are implemented in sequence. The whole tunnel is excavated method, without blasting, supplemented by advanced support and initial support, etc., to reduce the disturbance effect of tunnel excavation and reduce the deformation of surrounding rock after excavation.

The milling and excavation method of the shallow-buried large-section tunnel with weak cladding of the present invention follows the principle of "less disturbance, quick consolidation, frequent measurement, and early closure", and takes the stability and reinforcement of the interlayer rock pillar as the key point of construction. Compared with the existing construction method, it has the following advantages: Compared with the double-side-wall pilot pit method and the CRD method, it can reduce temporary supports and other supports and save costs; compared with the CD method, it can reduce the disturbance of the tunnel excavation to the surrounding rock, and can Strictly control the deformation of surrounding rock to ensure construction safety.

In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail below with reference to the accompanying drawings.

Description of drawings

The accompanying drawings constituting a part of this application are used to provide further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 is a schematic diagram of the method for milling and excavating a shallow-buried large-section tunnel with weak cladding in a preferred embodiment of the present invention; and

Figure 2 is a cross-sectional view of Figure 1 in a preferred embodiment of the present invention.

Explanation of reference numbers:

1. One rock mass on the right side wall of the upper pilot pit; 2. Two rock masses on the right side wall of the lower pilot pit; 3. Three rock masses on the right side wall of the lower pilot pit; 4. Four rock masses on the right side wall of the lower pilot pit ; 5. Five rock masses on the left side of the upper pilot pit; 6. Six rock masses on the left side of the lower pilot pit; 7. Seven rock masses on the left side of the lower pilot pit.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

Fig. 1 is a schematic diagram of a method for milling and excavating a shallow-buried large-section tunnel with weak cladding in a preferred embodiment of the present invention; Fig. 2 is a cross-sectional view of Fig. 1 in a preferred embodiment of the present invention.

As shown in Fig. 1 and Fig. 2, the method of milling and excavation for shallow-buried large-section tunnel with weak cladding in this embodiment uses the temporary support of the middle wall to divide the cross-section of the tunnel into a right pilot pit and a left pilot pit, and the temporary support of the middle wall The protection includes the temporary support of the middle wall of section A in the upper part and the temporary support of the middle wall of section B in the lower part. The right pilot pit is divided into a rock mass 1 on the right side wall of the upper pilot pit and a rock mass 1 on the right side wall of the lower pilot pit The rock mass on the right side wall of the lower pilot pit includes two rock masses 2 on the right side wall of the lower pilot pit, three rock masses 3 on the right side wall of the lower pilot pit and four rock masses on the right side wall of the lower pilot pit from left to right in the horizontal direction. Body 4, the left pilot pit is divided into five parts of the rock mass 5 on the left side wall of the upper pilot pit and the rock mass on the left side wall of the lower pilot pit according to the up and down, and the left side wall rock mass of the lower pilot pit is horizontally from left to right including the left side of the lower pilot pit. The six rock masses 6 on the side wall and the seven rock masses 7 on the left side wall of the lower pilot pit include the following steps:

S1. Perform advanced support on a part of the rock mass 1 on the right side wall of the upper pilot pit;

S2. Excavation of a part of rock mass 1 on the right side wall of the upper pilot pit, initial support I is performed on the right side of a part of rock mass 1 on the right side wall of the upper pilot pit, and about a part of rock mass 1 on the right side wall of the upper pilot pit Temporary support for the middle wall of section A is applied on the side, and advanced construction is applied to the second rock mass 2 on the right side wall of the lower pilot pit, the third rock mass 3 on the right side wall of the lower pilot pit, and the fourth rock mass 4 on the right side wall of the lower pilot pit. support;

S3. Excavate the rock mass 2 of the second part of the right side wall of the lower pilot pit, and temporarily support the middle wall of section B on the second rock mass 2 of the right side wall of the lower pilot pit;

S4. Excavate three rock masses 3 on the right side wall of the lower pilot pit and four rock masses 4 on the right side wall of the lower pilot pit, implement initial support II, and complete the initial support closure of the right pilot pit side wall to form a ring;

S5, perform advanced support on the five rock masses 5 on the left side wall of the upper pilot pit;

S6. Excavation of five rock masses 5 on the left side wall of the upper pilot pit, initial support III on the left side of the five rock masses 5 on the left side wall of the upper pilot pit, and six rock masses 6 on the left side wall of the lower pilot pit Seven parts of the rock mass 7 on the left side wall of the lower pilot pit are used as advance support;

S7. Excavate the six rock masses 6 on the left side wall of the lower pilot pit, and implement initial support IV on the left side of the six rock masses 6 on the left side wall of the lower pilot pit;

S8. Excavate the seven rock masses 7 on the left side wall of the lower pilot pit, and implement initial support V on the lower side of the seven rock masses 7 on the left side wall of the lower pilot pit, and complete the initial support closure of the left pilot pit side wall to form a ring;

S9. Steps S1 to S8 are repeated until all the excavation is completed, the temporary steel frame and temporary support are removed, and the inverted arch and secondary lining are poured.

The milling and excavation method of the shallow-buried large-section tunnel with soft and weak cladding of the present invention proposes a tunnel excavation method suitable for small clear distance, large section or super large section, poor surrounding rock conditions and extremely high requirements for surrounding rock deformation control , combined with the construction technology of CD method, CRD method and double-side-wall pilot pit method, and improved on the basis of CD method, the tunnel section is decomposed into 7 construction parts, and they are implemented in sequence. The whole tunnel is excavated method, without blasting, supplemented by advanced support and initial support, etc., to reduce the disturbance effect of tunnel excavation and reduce the deformation of surrounding rock after excavation.

The milling and excavation method of the shallow-buried large-section tunnel with weak cladding of the present invention follows the principle of "less disturbance, quick consolidation, frequent measurement, and early closure", and takes the stability and reinforcement of the interlayer rock pillar as the key point of construction. Compared with the existing construction method, it has the following advantages: Compared with the double-side-wall pilot pit method and the CRD method, it can reduce temporary supports and other supports and save costs; compared with the CD method, it can reduce the disturbance of the tunnel excavation to the surrounding rock, and can Strictly control the deformation of surrounding rock to ensure construction safety.

The method of milling and excavation of the above-mentioned shallow-buried large-section tunnel with soft cladding divides the tunnel into 7 parts for two purposes. A large number of engineering practices at this stage show that one of the main factors affecting the deformation of the tunnel surrounding rock is the exposure time of the excavation surface. The longer the exposure time, the greater the deformation of the surrounding rock. However, compared with the overall excavation of the rock mass 2 on the right side wall of the downpit by the traditional CD method, the time used for excavating the two parts of the rock mass 2 on the right side of the downpit must save a lot of time, which means that the right side of the downpipe The exposure time of the excavation surface on the left side of the rock mass 2 in the second part of the wall will be shortened. For example, when only the excavation volume is considered, the overall excavation time of the rock mass on the right side of the pilot pit is h, so the excavation alone The time for the second rock mass 2 on the right side wall of the pilot pit is only about 1/3h, and the exposure time of the excavation surface on the left side of the second rock mass 2 on the right side wall of the lower pilot pit can be shortened by about 2/3h. In addition, if the rock mass on the right side of the pilot pit is excavated as a whole, the excavation surfaces on both sides are exposed at the same time, and the risk is relatively high. Only one side of the excavation surface is exposed, and the unexcavated part can be used as core soil to reduce tunnel invert uplift. In addition, after the overall excavation of the rock mass on the right side of the lower pilot pit, the temporary support, initial support or advanced support for the middle wall of a part of the rock mass 1 on the right side of the upper pilot pit is in a suspended state, lacking support. Therefore, it is necessary to complete the temporary support of the middle wall of the rock mass on the right side of the pilot pit and the initial support II as soon as possible.

In this embodiment, except that the second rock mass 2 on the right side wall of the lower pilot pit is excavated by an excavator, the others are excavated by a milling excavator. Except for the above-mentioned rock mass 2 on the right side wall of the lower pilot pit, which is excavated by an excavator, the others are excavated by a milling excavator. As well as the excavation characteristics of milling excavators, combined with CD method, CRD method and double-side wall pilot pit method, the traditional mining method is improved, and it is an efficient support, which strictly controls deformation, ensures construction safety and is suitable for milling and excavation. The construction method of tunnels crossing the river by machine excavation. Moreover, the second rock mass 2 on the right side wall of the lower pilot pit is excavated by an excavator alone. The smaller the rock mass 2 on the right side wall, the better, but the size of the rock mass must take into account the space for mechanical construction operations. Based on the fact that the milling machine used in the project is too large, it is not suitable for excavating the second rock mass on the right side wall of the pilot pit. In addition, due to the limited size of the tunnel section, after satisfying the excavation size of the three rock masses 3 on the right side wall of the lower pilot pit and the four rock masses 4 on the right side wall of the lower pilot pit, the second There is not much space for the rock mass 2 in the lower part, so a smaller excavator is used for excavation

In this embodiment, the excavation footage of a part of the rock mass 1 on the right side wall of the upper pilot pit is one block, and a part of the rock mass 1 on the right side wall of the upper pilot pit is excavated for two blocks and then transferred to the second part of the right side wall of the lower pilot pit Rock mass 2 is excavated, and the excavation footage is two blocks. Temporary support is applied to the middle wall of section B, and gravel is backfilled, and then transferred to the third rock mass 3 on the right side wall of the lower pilot pit and the fourth rock mass on the right side wall of the lower pilot pit. Body 4 is excavated, and the excavation footage is two blocks, the initial support II is applied, and gravel is backfilled. The excavation of the two rock masses 2 on the right side wall of the lower pilot pit needs to be excavated ahead of the three rock masses 3 on the right side wall of the lower pilot pit and the four rock masses 4 on the right side wall of the lower pilot pit. two. The above-mentioned excavation is carried out in units of a block, and one block is one time the distance between I-beams. The I-beam is the lining bracket.

In this embodiment, the specific steps for excavating three rock masses 3 on the right side wall of the lower pilot pit and four rock masses 4 on the right side wall of the lower pilot pit include:

S41. Excavate the four rock masses 4 on the right side wall of the lower pilot pit, apply initial support to the right side of the four rock masses 4 on the right side wall of the lower pilot pit, and backfill gravel;

S42. Excavate the three rock masses 3 on the right side wall of the lower pilot pit, perform initial support on the lower side of the three rock masses 3 on the right side wall of the lower pilot pit, and backfill with gravel.

In the above-mentioned construction method, the specific steps of excavating the three rock masses 3 on the right side wall of the lower pilot pit and the four rock masses 4 on the right side wall of the lower pilot pit can be divided into two parts, first excavating the four parts on the right side wall of the lower pilot pit For rock mass 4, the initial support on the right side shall be applied immediately after excavation, and gravel shall be backfilled. Crushed rock, the initial support of the side wall of the right pilot pit is completed and closed into a ring. Dividing it into two parts is mainly to consider the characteristics of the milling machine’s own construction operation, and it is necessary to set an inclined slope to meet its driving needs. Therefore, the three rock masses 3 on the right side wall of the lower pilot pit in the middle part are set as The inclined slope can prevent the excavation surface from being adjacent to the inclined slope, thereby avoiding the deformation of the surrounding rock of the tunnel due to the long exposure time of the excavation surface. Preferably, the excavation surfaces of the three rock masses 3 on the right side wall of the lower pilot pit are inclined slope surfaces, and the inclination angle i1 of the excavation surfaces of the three rock masses 3 on the right side wall of the lower pilot pit is ≤16°.

The above method of milling and excavation for shallow-buried large-section tunnels with weak cladding is based on the large volume and weight of the milling machines required for the project, and ordinary construction methods are not applicable. It must be used for such large-volume, heavy-weight mechanical supporting construction methods. The stratum of the cross-river tunnel of this project is argillaceous siltstone with strong weathering and moderate weathering. The power of ordinary milling machines is too low to meet the excavation requirements. High-power milling and digging machines are very large in size, and the project based on this invention uses the STR260 milling and digging machine. The machine is about 16m long, 3.2m wide, 4.5m high, and weighs 100t. The excavation surface of body 3 is an inclined plane, the main purpose of which is to facilitate the up and down steps of the milling machine. The tunnel steel frame can no longer meet the requirements, and a long slope must be set separately. If the three rock masses 3 on the right side wall of the lower pilot pit are canceled, the excavation surface on one side will be adjacent to the slope. If the slope is close to the excavation surface, then The initial support or temporary support of this part of the excavation surface is often difficult to achieve, which will cause the excavation surface to be exposed for a long time, resulting in larger deformation of the surrounding rock, which is also contrary to the original intention of the present invention, so the right side wall of the lower pilot pit The rock mass is divided into 3 parts; while the rock mass on the left side wall of the lower pilot pit is only divided into two parts, because when excavating the rock mass 7 on the left side wall of the lower pilot pit, the middle wall of section B on the right side The temporary support has been built and the excavation surface is not exposed, so the seven rock masses 7 on the left side wall of the lower pilot pit are directly used as the driving slope of the milling machine.

As shown in Figure 2, in the present embodiment, the distance L5 in the depth direction between the excavation surface of the two rock masses 2 on the right side wall of the lower pilot pit and the top of the excavation surface of the third rock mass 3 on the right side wall of the lower pilot pit is 1m~ 1.5m; the height of backfill gravel ≥ 0.7m.

As shown in Fig. 1 and Fig. 2, in this embodiment, the lateral width L1 of the rock mass 3 in the three parts on the right side wall of the pilot pit is 3.2m-4m. In the above construction method, the 3 rock masses and the 7 rock masses must fully consider the width of the milling machine, the operating space of the milling machine, and the space required for the excavation of the pilot pit on both sides. The 3 rock masses on the right side of the pilot pit The horizontal width L1 of 3 is 3.2m-4m. The lateral width L2 of the seven rock masses on the left side wall of the pilot pit is 3.2m-5m.

As shown in Figure 2, in the present embodiment, the distance L3 in the depth direction between the excavation surface of a rock mass 1 on the right side wall of the upper pilot pit and the excavation surface of the second rock mass 2 on the right side wall of the lower pilot pit is 16m~ 20m; and/or, the distance L4 in the depth direction between the excavation surface of the four rock masses 4 on the right side wall of the lower pilot pit and the top of the excavation surface of the three rock masses 3 on the right side wall of the lower pilot pit is 18m-22m. According to site conditions, surrounding rock performance, construction method, tunnel section and excavation requirements, etc., calculate the length of each step and slope. The distance L3 in the depth direction between the excavation surface of a rock mass 1 on the right side wall of the upper pilot pit and the excavation surface of the second rock mass 2 on the right side wall of the lower pilot pit is greater than the length of the milling machine, and smaller than the length of the milling machine and the upper pilot pit. The sum of the excavation footage length of a rock mass 1 on the right side wall. Preferably, L3 is 16m-20m. The distance L4 in the depth direction between the excavation surface of the four rock masses 4 on the right side wall of the lower pilot pit and the top of the excavation surface of the three rock masses 3 on the right side wall of the lower pilot pit is determined by the slope, the height of the steps and the height of the backfilled gravel. Preferably, L4 is 18m-22m.

In this embodiment, the excavation footage of the five rock masses 5 on the left side wall of the upper pilot pit is one block, and the five rock masses 5 on the left side wall of the upper pilot pit are excavated for two blocks and then transferred to the six rock masses on the left side wall of the lower pilot pit. Body 6 was excavated, and the excavation footage was two blocks. Initial support IV was applied, and gravel was backfilled. Support Ⅴ, backfill gravel. The excavation footage of a rock mass 1 on the right side wall of the upper pilot pit and five rock masses 5 on the left side wall of the upper pilot pit shall not be greater than one block, while the rock mass on the right side wall of the lower pilot pit and the rock mass on the left side wall of the lower pilot pit, The footage of each excavation shall not exceed two blocks. In order to ensure that the construction progress of the upper and lower pilot pits is consistent, the initial support must be completed after each excavation of the upper pilot pit. Support after two days.

As shown in Fig. 1 and Fig. 2, in the present embodiment, the excavation surface of the seven rock masses 7 on the left side wall of the lower pilot pit is an inclined slope, and the inclination of the seven rock masses 7 excavation surfaces on the left side wall of the lower pilot pit The angle i2≤16°; and/or, the lateral width L2 of the rock mass at the 7 parts on the left side wall of the pilot pit is 3.2m-5m. The inclination angle i2≤16° of the excavation surface of the seven parts of the rock mass 7 on the left side wall of the lower guide pit is convenient for the milling machine to go up and down the steps. This part of the soil can be reinforced if necessary.

As shown in Figure 2, in this embodiment, the distance L7 in the depth direction between the excavation surface of the five rock masses 5 on the left side wall of the upper pilot pit and the top of the excavation surface of the seven rock masses 7 on the left side wall of the lower pilot pit is 16m ~20m; and/or, the distance L8 in the depth direction between the excavation surface of the six rock masses 6 on the left side wall of the lower pilot pit and the top of the excavation surface of the seven rock masses 7 on the left side wall of the lower pilot pit is 18m-22m. According to site conditions, surrounding rock performance, construction method, tunnel section and excavation requirements, etc., calculate the length of each step and slope. The distance L7 in the depth direction between the excavation surface of the five rock masses 5 on the left side wall of the upper pilot pit and the top of the excavation surface of the seven rock masses 7 on the left side wall of the lower pilot pit is greater than the length of the milling machine, and less than the length of the milling machine and the upper guide pit. The sum of the excavation footage lengths of the five rock masses 5 on the left side wall of the pit. The distance L7 in the depth direction between the excavation surface of the six rock masses 6 on the left side wall of the lower pilot pit and the top of the excavation surface of the seven rock masses 7 on the left side wall of the lower pilot pit is determined by the slope, the height of the steps and the height of the backfilled gravel.

In this example, the advance support adopts the advance small conduit grouting and pipe shed, the grouting small conduit L is 3m-4.5m, the pipe shed L is 3m-6m; the initial support I, the initial support III, the initial support Ⅳ. Initial support Ⅴ and initial support Ⅱ all adopt steel arch frame, shotcrete and mortar anchor, the mortar anchor L is 3.5m~4.5m; Concrete, advanced small conduit and mortar anchor, the L of the advanced small conduit is 3m to 4.5m, and the L of the mortar anchor is 3.5m to 4.5m.

In this embodiment, the safety distance L6 in the depth direction of the right pilot pit and the left pilot pit is 3m-5m; the distance L10 in the depth direction between the construction site of the inverted arch and the excavation surface of the six rock masses 6 on the left side wall of the lower pilot pit is 16m-18m ; The depthwise distance L11 between the secondary lining construction site and the inverted arch construction site is 8m to 12m.

Example

The method of milling and excavation for shallow-buried large-section tunnels with weak cladding, using the temporary support of the middle wall to divide the cross-section of the tunnel into a right pilot pit and a left pilot pit, and the safety distance L6 between the right pilot pit and the left pilot pit in the depth direction is 3m~5m , the temporary support of the middle wall includes the temporary support of the middle wall of section A and the temporary support of the middle wall of section B. The right pilot pit is divided into a rock mass 1 on the right side wall of the upper pilot pit and a rock mass on the right side wall of the lower pilot pit according to the vertical direction , the rock mass on the right wall of the lower pilot pit includes two rock masses 2 on the right wall of the lower pilot pit, three rock masses 3 on the right side wall of the lower pilot pit, and four rock masses on the right wall of the lower pilot pit from left to right in the horizontal direction 4. Divide the left pilot pit into five rock masses 5 on the left side wall of the upper pilot pit and the rock mass on the left side wall of the lower pilot pit according to the upper and lower sides. The rock mass 6 of the six parts of the wall and the rock mass 7 of the seven parts of the left side wall of the lower pilot pit comprise the following steps:

S1. Perform advanced support on a part of the rock mass 1 on the right side wall of the upper pilot pit;

S2. A part of rock mass 1 on the right side wall of the upper pilot pit is excavated by STR260 milling machine, and the excavation footage is one block. The depth direction distance L3 of the excavation surface of the rock mass is 16m ~ 20m, the initial support I is applied to the right side of a rock mass 1 on the right side wall of the upper pilot pit, and the rock mass 1 on the right side wall of the upper pilot pit is The middle wall of section A is temporarily supported on the left side, and the second rock mass 2 on the right side wall of the lower pilot pit, the third rock mass 3 on the right side wall of the lower pilot pit and the fourth rock mass 4 on the right side wall of the lower pilot pit are constructed. For advance support, a rock mass 1 on the right side wall of the upper pilot pit is excavated twice, and then transferred to the second rock mass 2 on the right side wall of the lower pilot pit for excavation;

S3. The second rock mass 2 on the right side wall of the lower pilot pit is excavated by an excavator. Stone, the height of backfilling crushed stone is ≥0.7m;

S4. The four rock masses 4 on the right side wall of the lower pilot pit are excavated by STR260 milling excavator. Transfer to the three rock masses 3 on the right side wall of the lower pilot pit and use an excavator to excavate, and the excavation footage is two. The transverse width L1 of the rock masses of the three parts on the right side wall of the pit is 3.2m to 4m. The distance L5 is 1m~1.5m, and the distance L4 in the depth direction between the excavation surface of the four rock masses on the right side wall of the lower pilot pit and the top of the excavation surface of the three rock masses on the right side wall of the lower pilot pit is 18m~22m. The lower side of the three rock masses 3 on the right side wall is initially supported, and the gravel is backfilled to complete the initial support of the side wall of the right pilot pit to form a ring;

S5, perform advanced support on the five rock masses 5 on the left side wall of the upper pilot pit;

S6. The five rock masses 5 on the left side wall of the upper pilot pit are excavated by STR260 milling excavator. The six rock masses 6 on the left side wall of the lower pilot pit and the seven rock masses 7 on the left side wall of the lower pilot pit are provided with advanced support, and the five rock masses 5 on the left side wall of the upper pilot pit are excavated twice and transferred to the lower pilot pit Excavation of six rock masses 6 on the left side wall;

S7. The six rock masses 6 on the left side wall of the lower pilot pit are excavated by STR260 milling excavator, and the excavation footage is two. Initial support IV is applied to the left side of the six rock masses 6 on the left side wall of the lower pilot pit, and gravel is backfilled ;

S8. The excavation of the seven rock masses 7 on the left side wall of the lower pilot pit is excavated by STR260 milling machine, and the excavation footage is two. The inclination angle i2 of the excavation face of the seven rock masses 7 on the left side wall of the lower pilot pit is ≤16°; The distance L7 between the excavation surface of the body and the top of the excavation surface of the seven rock masses 7 on the left side wall of the lower pilot pit is 16m to 20m. The distance L8 in the depth direction of the top of the excavation face of the Qibu rock mass 7 on the side wall is 18m to 22m. The initial support V is applied to the lower side of the Qibu rock mass 7 on the left side wall of the lower pilot pit, and gravel is backfilled to complete the left pilot pit. The initial support of the side wall is closed into a ring;

S9. Remove temporary steel frames and temporary supports, and pour inverted arches and secondary linings.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (12)

1. A method for milling and digging excavation of a shallow-buried large-section tunnel with weak cladding, is characterized in that the tunnel cross-section is divided into a right pilot pit and a left pilot pit by using the temporary support of the middle wall, and the temporary support of the middle wall includes the upper The temporary support of the middle wall of section A and the temporary support of the middle wall of section B at the lower part divide the right pilot pit into a rock mass (1) on the right side wall of the upper pilot pit and a rock mass on the right side wall of the lower pilot pit according to the upper and lower sides. The rock mass on the right wall of the pilot pit includes two rock masses on the right wall of the lower pilot pit (2), three rock masses on the right wall of the lower pilot pit (3) and four parts on the right wall of the lower pilot pit from left to right The rock mass (4) divides the left pilot pit into five rock masses (5) on the left side wall of the upper pilot pit and the rock mass on the left side wall of the lower pilot pit according to the vertical direction. Including six rock masses (6) on the left side wall of the lower pilot pit and seven rock masses (7) on the left side wall of the lower pilot pit, including the following steps: S1, perform advanced support on a rock mass (1) on the right side wall of the upper pilot pit; S2. A part of the rock mass (1) on the right side wall of the upper pilot pit is excavated, and initial support I is applied to the right side of a part of the rock mass (1) on the right side wall of the upper pilot pit, and a part of the right side wall of the upper pilot pit is The middle wall of section A is temporarily supported on the left side of the rock mass (1), and the second rock mass (2) on the right side wall of the lower pilot pit, the third rock mass (3) on the right side wall of the lower pilot pit and the The four rock masses (4) on the right side wall are used as advanced support; S3. Excavate the second rock mass (2) on the right side wall of the lower pilot pit, and temporarily support the middle wall of section B on the second rock mass (2) on the right side wall of the lower pilot pit; S4. Three rock masses (3) on the right side wall of the lower pilot pit and four rock masses (4) on the right side wall of the lower pilot pit are excavated, and initial support II is implemented, and the initial support of the right pilot pit side wall is closed to form a ring ; S5, carry out advance support to the rock mass (5) of five parts on the left side wall of the upper pilot pit; S6. Excavate the five rock masses (5) on the left side wall of the upper pilot pit, and implement initial support III on the left side of the five rock masses (5) on the left side wall of the upper pilot pit, and the six parts on the left side wall of the lower pilot pit The rock mass (6) and the seven rock masses (7) on the left side wall of the lower pilot pit are used as advance support; S7. Excavate the six rock masses (6) on the left side wall of the lower pilot pit, and implement initial support IV on the left side of the six rock masses (6) on the left side wall of the lower pilot pit; S8. Excavate the seven rock masses (7) on the left side wall of the lower pilot pit, and implement initial support V on the lower side of the seven rock masses (7) on the left side wall of the lower pilot pit, and complete the initial support of the left pilot pit side wall closed into a ring; S9. Steps S1 to S8 are repeated until all the excavation is completed, the temporary steel frame and temporary support are removed, and the inverted arch and secondary lining are poured. 2. The method for milling and digging excavation of shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, In step S2, a rock mass (1) on the right side wall of the upper pilot pit is excavated by a milling excavator; In step S3, the second rock mass (2) on the right side wall of the lower pilot pit is excavated by an excavator; In step S4, three rock masses (3) on the right side wall of the lower pilot pit and four rock masses (4) on the right side wall of the lower pilot pit are excavated by a milling machine; In step S6, the five rock masses (5) on the left side wall of the upper pilot pit are excavated by a milling excavator; In step S7, the six rock masses (6) on the left side wall of the lower pilot pit are excavated by a milling excavator; In step S6, the seven rock masses (7) on the left side wall of the lower pilot pit are excavated by a milling excavator. 3. The method for milling and digging excavation of shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, The excavation footage of a part of the rock mass (1) on the right side wall of the upper pilot pit is one block, and a part of the rock mass (1) on the right side wall of the upper pilot pit is excavated for two blocks and then transferred to the lower pilot pit The second part of the rock mass (2) on the right side wall is excavated, and the excavation footage is two blocks. The middle wall of section B is temporarily supported, and the gravel is backfilled, and then transferred to the third part of the rock mass (3) on the right side wall of the lower pilot pit. Excavate four parts of the rock mass (4) on the right side wall of the lower pilot pit, and the excavation footage is two blocks. Initial support II is used and gravel is backfilled. 4. The method for milling and digging excavation of shallow-buried large-section tunnels with weak cladding according to claim 3, characterized in that, The specific steps of excavating three rock masses (3) on the right side wall of the lower pilot pit and four rock masses (4) on the right side wall of the lower pilot pit include: S41. Excavate the four rock masses (4) on the right side wall of the lower pilot pit, apply initial support to the right side of the four rock masses (4) on the right side wall of the lower pilot pit, and backfill gravel; S42. Excavate the three rock masses (3) on the right side wall of the lower pilot pit, perform primary support on the lower side of the three rock masses (3) on the right side wall of the lower pilot pit, and backfill gravel. 5. The method for milling and digging excavation of shallow-buried large-section tunnels with weak cladding according to claim 4, characterized in that, The distance L5 in the depth direction between the excavation surface of the second rock mass (2) on the right side wall of the lower pilot pit and the top of the excavation surface of the third rock mass (3) on the right side wall of the lower pilot pit is _1m to 1.5m m; The height of the backfilled gravel is ≥0.7m. 6. The method for milling and digging excavation of shallow-buried large-section tunnels with weak cladding according to claim 4, characterized in that, The excavation surfaces of the three rock masses (3) on the right side wall of the lower pilot pit are inclined slope surfaces, and the inclination angle i ₁ of the excavation surfaces of the three rock masses (3) on the right side wall of the lower pilot pit is ≤16° ;and / or The lateral width _L1 of the three rock masses (3) on the right side wall of the lower pilot pit is 3.2m-4m. 7. The method for milling and excavating shallow-buried large-section tunnels with weak cladding according to claim 4, characterized in that, The depthwise distance _L3 between the excavation surface of a rock mass (1) on the right side wall of the upper pilot pit and the excavation surface of two rock masses (2) on the right side wall of the lower pilot pit is 16m to 20m; and / or The distance L ₄ in the depth direction between the excavation surface of the four rock masses (4) on the right side wall of the lower pilot pit and the top of the excavation surface of the three rock masses (3) on the right side wall of the lower pilot pit is 18m-22m. 8. The method for milling and excavating shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, The excavation footage of the five rock masses (5) on the left side wall of the upper pilot pit is one block, and the five rock masses (5) on the left side wall of the upper pilot pit are excavated for two blocks and then transferred to the lower pilot pit Excavate the six parts of the rock mass (6) on the left side wall, and the excavation footage is two blocks, implement initial support IV, backfill gravel, and then transfer to the seven parts of the rock mass (7) on the left side wall of the lower pilot pit for excavation. The excavation footage is two blocks, the initial support V is applied, and gravel is backfilled. 9. The method for milling and excavating shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, The excavation surface of the seven rock masses (7) on the left side wall of the lower pilot pit is an inclined slope, and the inclination angle i ₂ of the excavation surface of the seven rock masses (7) on the left side wall of the lower pilot pit is ≤16° ;and / or The lateral width L ₂ of the seven rock masses (7) on the left side wall of the lower pilot pit is 3.2m-5m. 10. The method for milling and excavating shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, The distance L ₇ in the depth direction between the excavation surface of the five-part rock mass (5) on the left side wall of the upper pilot pit and the top of the excavation surface of the seven-part rock mass (7) on the left side wall of the lower pilot pit is 16m to 20m ;and / or The distance L ₈ in the depth direction between the excavation surface of the six rock masses (6) on the left side wall of the lower pilot pit and the top of the excavation surface of the seven rock masses (7) on the left side wall of the lower pilot pit is 18m-22m. 11. The method for milling and excavating shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, The advanced support adopts advanced small conduit grouting and pipe shed, the grouting small conduit L is 3m to 4.5m, and the pipe shed L is 3m to 6m; The primary support I, primary support III, primary support IV, primary support V, and primary support II all use steel arches, shotcrete and mortar anchors, and the mortar anchor L is 3.5m to 4.5m; The temporary support of the middle wall adopts temporary steel arches, steel mesh, shotcrete, small lead pipes and mortar anchors. 12. The method of milling and excavation for shallow-buried large-section tunnels with weak cladding according to claim 1, characterized in that, The safety distance L ₆ in the depth direction between the right pilot pit and the left pilot pit is 3m to 5m; The distance _L10 in the depth direction between the construction place of the inverted arch and the excavation surface of the six rock masses (6) on the left side wall of the lower pilot pit is 16m～18m; The distance L ₁₁ in the depth direction between the secondary lining construction site and the inverted arch construction site is 8m to 12m.

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