CN101761346B - Method for constructing metamorphic rock confined water tunnel - Google Patents

Abstract

The invention relates to the field of tunnel engineering construction, in particular to a construction method of a metamorphic rock pressurized water tunnel, which solves problems such as geological disasters easily caused by existing methods, difficulty in controlling excavation contours, initial support deformation and cracking, and easy landslides, etc., including preliminary Predict the level of surrounding rock and the development of groundwater, accurately predict the geological situation and groundwater development in advance, drill in advance to release water and reduce pressure, advance small conduit grouting to consolidate surrounding rock and block water, select the excavation method of the cave body and determine Initial support form, construction of small radial conduits, excavation of inverted arches and pouring of inverted arch concrete, and application of secondary linings. After adopting this construction method, the excavation profile has been effectively controlled, the frequency of block collapse has been reduced and the scale has been reduced, the deformation and cracking of the initial support have been effectively controlled, and no secondary arch replacement has been performed, basically avoiding tunnel collapse; The cost is reduced, and the construction quality and construction safety are effectively improved, thereby creating good social benefits.

Description

Construction method of a metamorphic rock confined water tunnel

technical field

The invention relates to the field of tunnel engineering construction, in particular to a construction method for a metamorphic rock pressurized water tunnel.

Background technique

The surrounding rocks of metamorphic rock confined water tunnels are characterized by the development of joints and fissures, the joint surfaces are dense and smooth, and the rocks are in the form of massive or fragmented crushed structures. , Weak self-stabilization ability, multi-layer pressurized water causes water to flow out of the cave body after excavation and gradually become larger, or water will flow out and gradually become larger after a few days of no water after excavation. The support structure is stable and safe when no water comes out. Once the water comes out, the filling in the crack will soften and be lost with the water, which will deteriorate the integrity and stability of the surrounding rock, increase the pressure on the support system, and cause the water outlet part and its vicinity to be damaged. The support is cracked, the steel frame is deformed and broken.

At present, tunnel construction is carried out in the metamorphic rock confined water section. Due to the lack of deep understanding of the characteristics of the metamorphic rock mass and the underestimation of the harmful effects of the confined water, there is no reasonable and targeted construction plan during construction, and the traditional construction plan is still used. During construction, it is easy to cause geological disasters such as water inrush, mud inrush, and landslides. The excavation contour is difficult to control, over-excavation is serious, and block collapse occurs from time to time. It is easy to cause deformation and cracking of the primary support. The steel frame is twisted and broken. Invasion of the boundary, and even landslides. In addition, it is very difficult to work under the condition of pressurized water. The shotcrete will be washed away before it solidifies. During the welding operation, the welding fluid will be condensed before it can be welded. The grout is washed away before it solidifies, making it difficult to guarantee the construction quality, and the support system is easily deformed and cracked due to complex forces. The waterproof layer is not only difficult to lay and weld, but also easily damaged by pressurized water, resulting in water leakage from the secondary lining.

Contents of the invention

In order to solve the problems of existing metamorphic rock confined water tunnels using traditional tunnel construction methods, such problems as geological disasters are easily caused, excavation contours are difficult to control, initial support deformation and cracking are easy to collapse, and construction operations are difficult, etc., the present invention provides a metamorphic tunnel. Construction method of rock-confined water tunnel.

The present invention is realized by adopting the following technical scheme: a construction method of a metamorphic rock confined water tunnel, comprising the following steps: A. Preliminary prediction of surrounding rock level and groundwater development; According to the preliminary prediction conclusion, horizontal drilling rigs are used for advanced drilling detection in areas with confined water or water-rich areas and areas with complex geology. The lithology and structural characteristics of surrounding rocks can be accurately determined through core sampling, and the development of groundwater can be accurately determined through the water output of exploration holes. conditions and pressure conditions, the advanced exploration hole is drilled with the RPD-150C drilling machine Φ110mm drill bit, drilling once every 50m, and each drilling is 60m; The pressurized water section adopts advanced drilling to relieve water and reduce pressure, and the advanced drainage hole is drilled with a Φ91mm drill bit of the XY-2PC drilling machine, drilling once every 25m, the drilling depth is 30m, and 3 to 7 holes are drilled each time; Small conduit grouting to consolidate the surrounding rock and block water: within the range of 120°-180° of the arch of the tunnel body, a small conduit is constructed along the contour line of the tunnel excavation, and the cement-sodium silicate double slurry is injected, and the cement-sodium silicate double slurry is injected. Slurry parameters: cement slurry water-cement weight ratio is 1:1, mortar water glass volume ratio is 1:0.8, water glass modulus m=2.4~3.4, concentration Be=30~40, grouting pressure is controlled at 0.5~1.0 MPa, the grout diffusion radius is not less than 30cm; E selects the excavation method of the cave body and determines the initial support form: through advanced drilling and small conduits for advanced grouting, the metamorphic rock confined water tunnel is guided by the three-step method or the upper arc guide Reserve the core soil for construction with the three-step method, and at the same time apply the corresponding form of initial support; E is to make a small radial conduit: after the initial support is completed, a radial small conduit is used; G excavates the inverted arch and pours it Inverted arch concrete: After the excavation and support of the cave body is completed, the inverted arch E construction shall be carried out immediately. The length of excavation and concrete pouring for the inverted arch construction shall not exceed 6m at one time; the secondary lining for H: before the construction of the inverted arch is completed, the construction of the inverted arch shall be carried out through small The cement-water glass double slurry described in step D is poured into the conduit. The three-step method used in the excavation of the tunnel body or the three-step method of the upper arc guide to reserve the core soil are well known to those skilled in the art, and there are mature construction specifications in the field of tunnel construction. The initial support should be Strictly follow the design or specification requirements.

During construction, it is difficult to control the excavation profile of the metamorphic rock confined water tunnel, and it is very easy to lose blocks and collapse. The metamorphic rock confined water tunnel described in the present invention is excavated by the three-step micro-vibration controlled blasting method, and the drill and blast design , all peripheral holes arranged along the excavation contour line shall be connected in series with detonating cords, and the peripheral holes shall be in the form of interval charge (i.e., one blasthole is charged, and the two adjacent blastholes are only equipped with detonating cords); , the cutting holes are arranged according to the profile of the upper arc guide section. Adopting the drill-and-blast design of the present invention, compared with the traditional drill-and-blast design (all peripheral holes are filled with explosives, and the upper arc-guided cutting holes are arranged in a rectangle instead of being arranged according to the profile of the upper-arc-guided cross-section), the traditional blasting of one cubic meter 1.2-2.4Kg of explosives is needed for a section of 1.5 meters, but the present invention only needs 0.6Kg, which greatly reduces the amount of explosives, and can effectively reduce the disturbance of blasting waves to surrounding rocks, effectively control over-under-excavation, and reduce block loss and collapse. The present invention adopts micro-vibration controlled blasting excavation with short footage, multiple drill holes, and less powder charge. In actual construction, the tunnel blasting parameters are adjusted in time according to the occurrence and weakness of surrounding rock joints, and the best blasting effect is achieved.

During the construction of the metamorphic rock confined water tunnel, the present invention carefully analyzes the geological data provided by the design, and combines the advanced geological forecast data to preliminarily determine the level of surrounding rock and the development of groundwater in front of the tunnel face, and provide guidance for advanced drilling detection; Preliminary judgment results, targeted use of advanced drilling for accurate forecasting; after advanced drilling detection, according to the amount of water, advanced drilling into the drain hole, so that the front of the pressurized water can be released in advance, reduce the water pressure, and reduce the pressure for subsequent construction. Difficulty; before the excavation of the cave body, small conduits are used to reinforce the surrounding rock with advanced grouting, forming a grouting consolidation ring, improving the self-stability of the surrounding rock, blocking most of the groundwater in the vault beyond the excavation contour line, and providing convenience for construction operations Conditions: adopt short footage, more drilling holes, and less explosives to control the blasting excavation by micro-vibration, reduce the disturbance of the blasting shock wave to the surrounding rock, improve the excavation effect, and reduce the loss of blocks and collapse; after the initial support is completed, the construction Make radial small conduits and use them as weep holes to drain water in the early stage to slow down the destructive effect of confined water on the initial support. Once the initial support deforms and cracks or is about to be lined, radial grouting reinforcement will be carried out through radial small conduits Surrounding rock and blocked water again.

In a word, the present invention adopts a series of measures of "exploring-releasing-blocking-draining-blocking" for the characteristics of confined water, effectively controlling the hazards and destructive effects of confined water, improving construction conditions, ensuring construction quality and construction safety, and improving At the same time, according to the lithological characteristics of metamorphic rock, this method adopts small conduit advance grouting and small conduit radial grouting to strengthen the surrounding rock, which effectively improves the rock mass structure and improves the self-stabilization ability of the surrounding rock; Micro-vibration controlled blasting with footage, more drilling, and less charge can effectively reduce the disturbance of the blasting shock wave to the surrounding rock, improve the excavation effect, and reduce the loss of blocks and collapse. After adopting this construction method, the excavation profile has been effectively controlled, the frequency of block collapse has been reduced and the scale has been reduced, the deformation and cracking of the primary support have been effectively controlled, and there has been no secondary arch replacement, basically avoiding tunnel collapse. After adopting this construction method, an average of 4m ³ of over-excavation and 4m ³ of over-excavation shotcrete are reduced per linear meter, and the cost is reduced by about 3,500 yuan; the average cost of dealing with block collapse, primary support deformation, cracking and landslide is reduced by about 3,000 yuan per linear meter; The average cost increase per linear meter is about 5,000; the total average cost reduction per linear meter is about 1,500 yuan. The adoption of this construction method not only reduces the cost, but also effectively improves the construction quality and construction safety, thereby creating good social benefits. It is suitable for All metamorphic rock confined water tunnel construction.

Description of drawings

Fig. 1 is a block diagram of construction technological process of the present invention;

Fig. 2 is the three-step construction process diagram of the metamorphic rock confined water tunnel of the present invention;

Fig. 3 is a schematic diagram of the layout of the advanced detection hole and the advanced drainage hole of the present invention;

Fig. 4 is a layout diagram of the monitoring measurement points of the present invention;

Fig. 5 is the drilling and blasting design drawing of the excavation face of the metamorphic rock confined water tunnel of the present invention

Fig. 6 is a schematic diagram of the structure of the peripheral eye charge in Fig. 5;

In the figure: 1-advance probe hole; 2-advance drain hole; 3-tunnel excavation contour line; 4-advance small duct; 5-radial small duct; 6-peripheral eye; 7-detonating cord; 8- Upper arc guide; 9-cut hole; 10-middle guide A; 11-middle guide B; 12-down guide C; 13-down guide D; 14-inverted arch E; mud; 17 - non-electric millisecond detonator.

Detailed ways

A construction method of a metamorphic rock confined water tunnel, as shown in Figure 1, comprises the following steps:

A Preliminary prediction of surrounding rock level and groundwater development: large or special geological structures and basic geological conditions are generally marked on the geological data provided by the design, and the tunnel geological segment can be predicted in time through the TSP203 geological prediction system, which can be predicted relatively accurately The geological structure and groundwater development of the upcoming construction section. Preliminary conclusions can be drawn through careful analysis of design geological data and TSP system forecast data, and guidance will be provided for whether to implement or in which section to adopt advanced sounding prediction in the next step. Due to the dense joints of the metamorphic rock confined water tunnel and the broken surrounding rock rich in fissure water, the prediction range of the TSP system is limited. In order to improve the accuracy of the prediction, it is required to make a prediction every 80m;

B. Preliminary exploration to accurately predict geological conditions and groundwater development: According to preliminary prediction conclusions, horizontal drilling rigs are used for advanced drilling detection in areas with confined water or water-rich areas and areas with complex geology, and the lithology of surrounding rocks can be accurately determined through core sampling , structural characteristics, accurately determine the development of groundwater and its pressure status through the water output of the probe hole, so as to make an accurate judgment for the construction method, support form and support parameters of the tunnel, and whether to adopt advanced drilling to discharge water. Exploration hole 1 is drilled with the RPD-150C drilling machine Φ110mm drill bit, drilling once every 50m, and drilling 60m each time. The RPD-150C drilling machine is an existing known equipment;

C. Advanced drilling for drainage and depressurization: According to the results of advanced drilling detection, advanced drilling for drainage and depressurization of water-rich and confined water areas can also be used to further ascertain the geological conditions to provide guidance for construction. Advanced drainage hole 2 XY-2PC drilling machine Φ91mm drill bit is used for drilling, drilling once every 25m, the drilling depth is 30m, and 3 to 7 holes each time. The water output and water pressure of the holes determine the number of drain holes. At first, 3 holes can be drilled, and if the water output is large, then 4 holes can be drilled. The XY-2PC drilling machine is an existing known equipment;

D. Advance small conduit grouting to consolidate the surrounding rock and block water: within the range of 120-180° of the tunnel body arch, along the tunnel excavation contour line 3, advance small conduit 4, inject cement-water glass double slurry, on the one hand, solidify Consolidating the surrounding rock improves the self-stabilizing ability of the surrounding rock. In addition, to form a grouting consolidation circle, most of the groundwater in the arch can be blocked beyond the excavation contour line, providing convenient conditions for the next construction operation. The small duct for advance grouting is processed into a tapered flower tube with Φ42*4 seamless steel pipe, the length is not less than 250cm, the circumferential distance is 30cm, and the horizontal overlap between rings is not less than 100cm. Cement-water glass double slurry parameters: cement slurry water-cement weight ratio is 1:1, mortar water glass volume ratio is 1:0.8, water glass modulus m=2.4~3.4, concentration Be=30~40, grouting pressure It is controlled at 0.5-1.0MPa, and the grout diffusion radius is not less than 30cm; the above-mentioned grout ratio and grouting parameters are obtained by the applicant through long-term engineering practice and experience summary, which ensures the effect of grouting, surrounding rock consolidation and water blocking effect very good;

中空注浆锚杆，80×80cm梅花形布置；

连接筋环向间距100cm，沿钢架内外两侧交错布置；钢筋网采用

钢筋加工，网格15×15cm；采用C25喷射混凝土，厚度不小于20cm。初期支护参数也可按设计标准施做，但不得低于上述指标。开挖和支护要严格按照规范要求进行施做，确保施工质量。E Select the excavation method of the tunnel body and determine the initial support form: after the advance drilling and drainage and the small conduit advance grouting, the construction of the metamorphic rock confined water tunnel is carried out according to the three-step method or the three-step method with the core soil reserved on the upper arc guide At the same time, the corresponding form of initial support is carried out; the initial support adopts I18 steel frame with a distance of 80-100cm; the length of the anchor rod of the system is not less than

Hollow grouting anchor rod, 80×80cm plum blossom arrangement;

The circumferential spacing of the connecting bars is 100cm, and they are arranged staggered along the inner and outer sides of the steel frame; the steel mesh adopts

Reinforcement processing, grid 15×15cm; C25 sprayed concrete, thickness not less than 20cm. Initial support parameters can also be implemented according to design standards, but not lower than the above indicators. Excavation and support shall be carried out in strict accordance with the specification requirements to ensure the construction quality.

The construction process of the above-mentioned three-step method is as follows, as shown in Figure 2:

a. When the pre-grouting strength of the small conduit is reached, according to the construction principle of "short footage, strong support", the upper arc guide 8 is excavated, and the initial support I is applied, and the circular footage is 80-100cm;

b. Start the construction of the intermediate guide 3~5m ahead of the upper arc guide, excavate the intermediate guide A and the intermediate guide B alternately, and implement the initial support of the intermediate guide Part II and Part III. The construction length shall not exceed two arches (160-200cm);

c. Start the down-guiding construction 3-5m ahead of the medium guide, excavate the down-guiding C and down-guiding D alternately, and implement the initial support of the medium-guiding part IV and V, and the left and right parts should not be less than 2m apart. The length shall not exceed two arches (160-200cm);

F: Make small radial conduits: in order to prevent the initial support from sealing the water outlet channel, increase the water pressure, and cause deformation and cracking of the initial support, make radial small conduits 5 after the initial support is completed; The small conduit is processed into a tapered flower tube with Φ42*4 seamless steel pipe, the length is not less than 250cm, and it is arranged in a quincunx shape of 2.5×2.5m. The radial small conduit is used as a weep hole in the early stage to discharge water. Once the initial support cracks or is about to be lined, the cement-sodium silicate double slurry is injected through the small conduit to further strengthen the surrounding rock and block water. Advance small catheter pre-grouting execution;

G Excavate the inverted arch and pour the inverted arch concrete: After the excavation and support of the cave body is completed, the inverted arch E (14) construction will be carried out immediately. 1. Inverted arches and inverted arches shall be filled with concrete layered and poured in layers, and the construction techniques and technical indicators of inverted arches must meet the design or specification requirements;

H to do the secondary lining VII: before the construction of the inverted arch is completed and the lining is completed, the cement-sodium silicate double slurry described in step D is poured through the small conduit to further strengthen the surrounding rock and block the water. Before laying the waterproof board, the parts with large water seepage shall be paved and hung with PE drainage board and blind drainage pipe for centralized drainage. The waterproof board adopts a PVC composite waterproof board with a thickness of not less than 1.5mm. The construction process of the waterproof board is strictly controlled to prevent sharp objects such as steel bars from piercing the waterproof board, so as to ensure the construction quality of the waterproof board and prevent water leakage from the secondary lining. The secondary lining concrete is integrally poured with a full-section hydraulic lining trolley. The construction techniques and technical indicators of the lining must meet the design or specification requirements;

I blasting excavation: The excavation surface of the metamorphic rock confined water tunnel is excavated by the three-step micro-vibration control blasting method (that is, according to the three steps of upper arc guide, middle guide and lower guide). All the peripheral eyes 6 arranged in the line are connected in series with detonating cord 7, and the peripheral eyes adopt the form of interval charging, as shown in Figure 5, the peripheral eyes marked with 13 are charged, and the peripheral eyes without numbers are only equipped with detonating cords. The hole is charged as shown in Figure 6, and the charge table according to the above-mentioned drilling and blasting design drawing is shown in Table 1 below; when the upper arc guide 8 is blasted, the cutting hole 9 is arranged according to the outline of the upper arc guide section, as shown in Figure 5 It shows that the blast holes marked with numbers 3, 5, and 7 are cut holes. It can be seen from the figure that the arrangement form is centered on the hollow hole in the center of the arc guide, distributed symmetrically to both sides, and three cut holes are formed from the inside to the outside. The slot hole, two cut holes and one cut hole are arranged in an arrangement form to form a shape that matches the profile of the upper arc guide section. Adopting this drilling and blasting design can not only reduce the dosage of chemicals, but also reduce the impact of blasting waves on the surrounding area. Rock disturbance, and can achieve the best blasting effect.

Table 1

In the above-mentioned process, the monitoring and measurement work must follow the excavation and support operations for point layout and monitoring. The measurement data shall be analyzed and fed back in time using the engineering analogy method, and the support parameters shall be adjusted to ensure the safety of construction and structure. The specific methods are as follows :

During the construction of the metamorphic rock confined water tunnel, a group of measurement sections is arranged every 10m, and each section is arranged with a vault sinking measurement point and two horizontal clearance convergence measurement baselines. The layout of the measuring points is shown in Figure 4, where a is the measuring point for the vault sinking, and b and c are the two baselines for measuring the convergence of the horizontal clearance.

The same measurement frequency is used for the headroom level convergence measurement and the vault sinking measurement. The measurement frequency is shown in Table 2. The actual measurement frequency is selected from the table according to the deformation speed and the distance from the excavation face. frequency. The horizontal convergence measurement is carried out with a laser profiler. After the excavation, the measuring points are quickly installed and numbered as required, and the initial reading is taken within 12 hours after the excavation. The sinking of the vault is measured with a laser profiler, a precision level, an extensometer, and an indium tile ruler, and points are quickly set on the vault after spraying the concrete.

Table 2

In order to further prove the beneficial effect of this construction method, the applicant cites the following engineering examples to prove it:

The Jiubao Tunnel of the Zhangji Railway is located in the south of the complex east-west structural belt of the Yinshan Mountains, at the boundary between the Yanshan subsidence zone of the Sino-Korean quasi-platform and the Inner Mongolia axis. In the geological history, it has experienced three periods of obvious tectonic movements: Pre-Sinian, Mesozoic and Cenozoic. The superposition of multi-stage tectonic movements has made the geological structure extremely complex. The scope of the cave body is all Archean metamorphic rocks, mainly granulite and shallow grainstone, and partially intruded into granitic pegmatite and diabase dikes. Due to the difference in the composition of the original rock and the influence of multi-stage tectonic movements, the development of structural joints and fissures is different. In addition, the intrusion of multi-stage dikes and the cutting and blocking of faults have formed water-bearing and water-resistant structures in some sections and layers. Confined aquifers are formed. The surrounding rock of the tunnel is characterized by the development of joints and fissures, the joint surface is dense and smooth, the rock is in the form of massive or fragmented crushed structures, the strength of the rock itself is high, and it is mixed with thin layers of weak fillings, the integrity of the surrounding rock is poor, and the self-stabilization ability is weak , multi-layer pressurized water causes water to flow out of the cave body after excavation and gradually become larger, or there is no water at that time after excavation, and water will flow out and gradually become larger after a few days.

The above-mentioned Jiubao Tunnel of Zhangji Railway is a metamorphic rock-bearing water tunnel, and traditional construction methods are used in the construction process, which has the problems recorded in the background technology of the present invention. However, after adopting the method described in the present invention, the excavation profile is effectively controlled, the occurrence frequency of falling block collapse is reduced and the scale is reduced, the deformation and cracking of the initial support are effectively controlled, and no secondary arch change is performed, basically avoiding The tunnel collapsed. The accumulative length of the metamorphic rock confined water tunnel constructed according to this construction method in the Jiubao Tunnel of Zhangji Railway is 5385m, and the accumulative cost reduction is about 8.07 million yuan.

Claims (2)

1. A construction method of a metamorphic rock confined water tunnel is characterized in that it comprises the following steps: A Preliminary prediction of surrounding rock grade and groundwater development; B Accurately predict the geological conditions and groundwater development in advance: according to the preliminary prediction conclusion, use horizontal drilling rigs for advanced drilling detection in areas with confined water or water-rich areas and areas with complex geology, and accurately determine the lithology of surrounding rocks through core sampling , Structural characteristics, accurately determine the development of groundwater and its pressure status through the water output of the probe hole, the advanced probe hole (1) uses the RPD-150C drilling machine Φ110mm drill bit to drill, drill once every 50m, and drill 60m each time; C Advanced drilling for drainage and pressure reduction: According to the detection results of advanced drilling, advanced drilling is used for drainage and pressure reduction in water-rich and confined water sections. The advanced drainage hole (2) is drilled with XY-2PC drilling machine Φ91mm drill bit , drilling once every 25m, drilling depth 30m, 3 to 7 holes each time; D Consolidate the surrounding rock by grouting and block water in small conduits in advance: within the range of 60° on both sides of the top of the arch of the tunnel body, construct small conduits in advance (4) along the tunnel excavation contour line (3), and inject cement-sodium silicate Double slurry, cement-water glass double slurry parameters: cement slurry water-cement weight ratio is 1:1, mortar water glass volume ratio is 1:0.8, water glass modulus m=2.4~3.4, concentration Be=30~40 , the grouting pressure is controlled at 0.5-1.0MPa, and the grout diffusion radius is not less than 30cm; E Select the excavation method of the tunnel body and determine the initial support form: After the advance drilling and drainage and the small conduit advance grouting, the construction of the metamorphic rock confined water tunnel is carried out according to the three-step method or the three-step method of the upper arc guide with the core soil reserved , and at the same time carry out corresponding forms of primary support; F Apply small radial catheters: after the initial support is completed, small radial catheters (5) are applied; G Excavate the inverted arch and pour the inverted arch concrete: After the excavation and support of the cave body is completed, the inverted arch construction will be carried out immediately, and the length of excavation and pouring concrete for the inverted arch construction shall not exceed 6m; H Apply the secondary lining: before the construction of the inverted arch is completed and the lining is completed, the cement-sodium silicate double slurry described in step D is poured through the small conduit. 2. The construction method of a metamorphic rock confined water tunnel according to claim 1, characterized in that the excavation surface of the metamorphic rock confined water tunnel adopts three-step micro-vibration control blasting method for excavation, and during drilling and blasting design, along the All the peripheral eyes (6) arranged in the excavation contour line are connected in series by detonating cord (7), and the peripheral eyes are in the form of interval charges; when the upper arc guide (8) is blasted, the cutting eyes are arranged according to the profile of the upper arc guide section ( 9). the

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