CN114718585A - A shield construction method suitable for passing through tidal lakes - Google Patents

Abstract

The invention provides a shield construction method suitable for passing through a tidal lake, which comprises the following steps: firstly, carrying out real-site survey on a site, determining the range of unfavorable geology in a tidal lake region, and marking stratums in the range as grouting stratums; cofferdams are arranged in the grouting stratum in different areas to reduce the water level of the tidal lake, and grouting pipes are inserted in the cofferdams and used for injecting grout to reinforce the unfavorable geology in the tidal lake area; after grouting is finished, starting the shield machine to carry out tunneling work, setting the cofferdams again in different areas in the tunneling process to reduce the influence of tide water level change on the tunneling process of the shield machine, simultaneously adjusting the pressure in a front cabin of the shield according to the tide rule, increasing the pressure of a soil cabin when the tide rises, and reducing the pressure of the soil cabin when the tide falls. The technical problem of potential safety hazards existing when the shield passes through the tidal lake in the sea-filling area in the prior art is solved.

Description

A shield construction method suitable for passing through tidal lakes

technical field

The invention relates to the technical field of shield tunnel construction, in particular to a shield construction method suitable for passing through a tidal lake.

Background technique

With the rapid development of my country's economy and the acceleration of urbanization, the increase of urban population has brought increasing pressure on urban traffic. Traffic congestion and the deteriorating urban environment have become common and urgent problems in major cities. As a safe, fast, efficient and environmentally friendly form of transportation, urban subway has quickly become the first choice for many large cities to solve traffic problems. In the process of urban subway construction, most subway tunnels are constructed by the shield method; due to the urban hydrogeological characteristics and the necessity of line planning, in the process of urban subway shield construction, it is inevitable to cross rivers, lakes and seas.

When the shield tunnel passes through the tidal lake in the reclamation area, the geology is complicated, the water level is affected by the tide, and the improper setting of the soil pressure in the earth pressure balance shield during the excavation of the shield can easily cause the lake bottom to subsidence or uplift, so that the lake water and the soil warehouse are connected, resulting in excavation risks; The self-stability of the overlying soil above the interval is poor, and there are boulders and bedrock protrusions within the interval, the stratum is unevenly soft and hard, the tunneling speed of the shield machine is unstable, and it is difficult to drive, which is very likely to cause the screw machine to spout and the pressure of the soil bin is unstable. , the tunnel face is unstable, and the lake surface subsides and uplifts; the boulders and bedrock protrusions in the reclamation area can easily cause wear to the shield cutter cutter head, resulting in no footage of the shield tunneling machine, passively opening warehouses at the bottom of the lake, and increasing construction. Risk, seriously endanger the shield construction.

Therefore, there is an urgent need for a shield construction technology suitable for passing through the tidal lake, so as to ensure the safety of the construction process and the shield tunneling process.

SUMMARY OF THE INVENTION

Based on this, the purpose of the present invention is to provide a shield construction method suitable for passing through tidal lakes, so as to solve the technical problem of potential safety hazards when shields pass through tidal lakes in reclamation areas in the prior art.

The invention provides a shield construction method suitable for passing through a tidal lake, the method comprising:

First conduct on-the-spot investigation to determine the range of unfavorable geology in the tidal lake area, and mark the strata within the range as grouting strata;

Cofferdams are arranged for the grouting strata in different areas to lower the water level of the tidal lake, and a grouting pipe is inserted in the cofferdam, and the grouting pipe is used for injecting slurry to reinforce the poor geology in the tidal lake area;

After the grouting is completed, the shield machine is activated to carry out the excavation work. During the excavation process, cofferdams are set again in different areas to reduce the influence of tidal water level changes on the excavation process of the shield machine. The internal pressure increases the soil bin pressure during high tide, and reduces the soil bin pressure during ebb tide.

Further, in the shield construction method suitable for passing through a tidal lake, the slurry includes cement and water glass, and the ratio of the cement and water glass is 1:1.

Further, in the shield construction method suitable for passing through a tidal lake, the number of grouting pipes in the cofferdam is not less than 3/m ² .

Further, in the shield construction method suitable for passing through a tidal lake, wherein the grouting pipe is made of PVC pipe.

Further, in the shield construction method suitable for passing through a tidal lake, the shield machine is an earth pressure balance shield, and a spoke-panel cutter head is selected.

Further, in the shield construction method suitable for passing through the tidal lake, when the shield machine is excavated to 50m outside the tidal lake, the excavation speed is reduced to increase the pressure of the soil bunker.

Further, according to the shield construction method suitable for passing through the tidal lake, after the shield machine passes through, the back grouting work of the shield segment is performed, and the internal force change and leakage of the segment are monitored at the same time. And further do a good job of replenishing pulp.

Further, in the shield construction method suitable for passing through a tidal lake, the number of cofferdams in the grouting formation is at least three.

To sum up, compared with the prior art, the present invention has the beneficial effect that: by reinforcing the unfavorable geology in the tidal lake area, the shield can be used in complex formations containing boulders, bedrock protrusions, medium sand, etc. The construction under the tidal lake area greatly improves the working environment, greatly reduces the construction risk of shield tunneling through the tidal lake, and effectively prevents the risks of abnormal lake surface, sand gushing and water gushing. It has a high degree of automation and overall high construction safety quality. In the process of excavation, cofferdams are set up again in different areas to reduce the impact of tidal water level changes on the excavation process of the shield machine. At the same time, according to the law of tides, the pressure in the warehouse in front of the shield machine is adjusted to avoid the high risk of opening warehouses at the bottom of the lake. The working condition solves the technical problem of potential safety hazards in the prior art when the shield passes through the tidal lake in the reclamation area.

Description of drawings

Fig. 1 is the flow chart of the shield construction method that is suitable for going down through the tidal lake in the present invention;

Fig. 2 is the schematic diagram of grouting in the present invention;

Fig. 3 is the tunneling schematic diagram of shield machine in the present invention;

The following specific embodiments will further illustrate the present invention with reference to the above drawings.

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the related drawings. Several embodiments of the invention are presented in the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and similar expressions are used herein for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Please refer to FIG. 1 , a flowchart of a shield construction method suitable for passing through a tidal lake in the first embodiment of the present invention, including the following steps:

Step S101, first conduct on-the-spot investigation to determine the range of unfavorable geology in the tidal lake area, and mark the strata within the range as grouting strata;

Specifically, before construction, the site shall be surveyed, the hydrogeological conditions of the site shall be checked, suitable materials shall be selected and prepared;

Step S102, setting cofferdams on the grouting formation sub-regions to lower the water level of the tidal lake, and inserting grouting pipes in the cofferdams, the grouting pipes are used for injecting slurry, so as to carry out the treatment of poor geology in the tidal lake area. reinforcement;

Specifically, the number of cofferdams in the grouting formation is at least 3, which are generally divided into 3 areas, which can be adjusted according to actual conditions. After grouting is completed, the cofferdams are removed. The slurry includes cement and water glass, the ratio of the cement and water glass is 1:1, and the number of grouting pipes in the cofferdam is not less than 3/m ² .

In step S103, after the grouting is completed, the shield machine is activated to carry out the excavation work. During the excavation process, cofferdams are set up again in different areas to reduce the influence of tidal water level changes on the excavation process of the shield machine, and at the same time, the shield is adjusted according to the law of tides. The pressure in the front silo is increased, the pressure of the soil bunker is increased when the tide is high, and the pressure of the soil bunker is reduced when the tide is low.

Please refer to FIG. 2 to FIG. 3, which show the schematic diagram of grouting and the schematic diagram of shield tunneling in the application, wherein 1 is the lake surface, 2 is the lake bottom, 3 is the cofferdam, 4 is the grouting pipe, 5 is the slurry, and 6 is the grouting pipe. 7 is the soil reinforcement area, and 7 is the shield machine.

For ease of understanding, taking the planning and design of a project as an example, Yundang Lake is a saline artificial lake with a water area of about 1.5 square kilometers. The lake water is connected to the sea water, and the water level is affected by the tide. The water depth is generally in the range of 2-6m; the main geology in the interval is: the average of the mixed fill is 2.3m, the average of the silt is 1.8m, the average of the silty clay is 7.7m, the average of the gravel is 2.5m, and the average of the residual sandy clay is 3m. , The average of all weathered granite is 2.5m.

Overall construction plan: first conduct on-the-spot investigation, clarify the scope of grouting stratum, and prepare for construction; as shown in Figure 1, set up cofferdams in different areas, and use PVC grouting pipes after lowering the water level, and use 1:1 cement and Water glass double-liquid grouting, the number of grouting holes is not less than 3/m2, after the grouting is completed, remove the cofferdam; do the preparations before the shield tunneling, and start the shield tunneling work. When the shield tunneling machine is 50m away from the tidal lake, the tunneling speed is reduced to increase the pressure of the soil bunker. During the tunneling process, cofferdams are set up again in different areas to reduce the impact of tidal water level changes on the shield tunneling process. Regularly, adjust the pressure in the warehouse in front of the shield, specifically: increase the pressure of the soil warehouse by 0.1MPa during high tide, and reduce the pressure of the soil warehouse by 0.1MPa when the tide is low; after the shield passes, the back grouting work of the shield segment should be carried out in time, and timely monitoring Changes in the internal force of the segment and the situation of water leakage, and further do a good job of replenishing the slurry.

Key construction techniques:

1. Ground reinforcement construction

Investigate the site before construction, check the hydrogeological conditions of the site, select and prepare suitable materials; measure and stake out according to the drawings, determine how to divide the cofferdam position, and then set up cofferdams in different areas. After lowering the water level, use PVC injection molding. For the grout pipe, the grout is grouted with 1:1 cement and water glass double-liquid grouting. After the grouting is completed, the cofferdam is removed.

(1) Scope of stratum reinforcement treatment

①Sand area

Reinforcement length: the left line of the interval is ZDK3+910～978, and the length is 68m; the right line of the interval is YDK3+895～YDK4+989, and the length is 94m.

Reinforcement width: 3m on each side of the tunnel body and on both sides.

Reinforcement depth: The 10m range of the shield opening reinforcement area is from 1m above the top of the tunnel to 1m below the bottom of the tunnel. The reinforcement depth of the sand layer is 1m above the sand layer and 1m below the sand layer.

②Boulder area (active opening point)

Reinforcement length: ZDK3+910～ZDK3+920 on the left line of the interval; ZDK3+997～ZDK3+999;

Reinforcement width: 3m outside the tunnel body.

Reinforcement depth: 1m above the top of the tunnel to 1m below the bottom of the tunnel.

(2) Arrangement of grouting holes

① Sand layer area: The spacing between the boreholes in the tunnel body is 3m, with a plum-shaped arrangement; a single row of boreholes are arranged on both sides of the tunnel body, the holes are 2m away from the tunnel outline, and the hole spacing is 1.5m.

②Boulder and bedrock areas: A single row of drilling holes is used around the reinforcement area with a spacing of 1.5m, and the drilling spacing in the middle reinforcement area is 3m.

For the reinforcement area with poor coring effect and bubbling in the lake during the shield pressure keeping process, the pre-buried pipe shall be filled with double-liquid slurry. The grouting sequence of the pre-embedded grouting pipe area is from small mileage to large mileage, first the left line, then the right line, first the side lines on both sides, then the interior, and the closed area first and then the filling area.

(3) Detection method after stratum reinforcement treatment is completed

①Use the drilling core-pulling method to do the compressive test, and the 28d unconfined compressive strength is required to be ≥0.2MPa;

② The random in-situ standard penetration test shall be adopted, and the number of standard penetration strikes shall not be less than 10.

③Sample inspection according to 1% of the number of holes, and the pressurized water inspection of the quality inspection holes should be carried out 7 days after the completion of grouting in the unit project.

According to the design requirements, one of the above methods can be selected.

2. Shield tunneling construction control

2.1. Targeted design of shield machine

(1) The basic structure of the cutter head

The basic structure of the cutter head is the spoke-panel type, the cutter head adopts the structure of four corbels, four main beams + four sub-beams, which can be installed with a hob, and the cutter seat can realize the exchange of the hob and the tearing knife, which is a composite cutter head . The excavation diameter of the cutterhead is Φ6480mm, the opening rate is 34%, and the openings are evenly distributed, which is conducive to the flow of muck and is not easy to produce mud cakes.

When the cutter head passes through the upper and lower hard formations, the eccentric load force is large, and the cutter head is required to have sufficient rigidity and strength. According to the detailed investigation report of this project, it is revealed that the maximum strength of medium-weathered granite and lightly-weathered granite is 43.5-104Mpa. Due to the complex structure of the cutter head, the force calculation needs to use the finite element method for force analysis. Through the optimized design, the force of the cutter head can be used in formations with a stress below 150MPa. This type of cutter head has sufficient rigidity and strength. Under the condition of large eccentric load on the upper soft and lower hard sections, the cutter head deforms within the elastic deformation range. within. The rigidity and strength of this type of cutter head can meet the needs of this project.

(2) Tool configuration

According to the characteristics of the stratum, the maximum strength of the rock formation is 104MPa, and the tearing knife cannot cut high-strength rock, so a hob needs to be equipped. Due to the uneven strength of the rock formation, the minimum 12.7MPa, the maximum 104MPa, the impact-resistant 17-inch hob is selected, and the cutter head is equipped with There are 6 center duplex reels, 35 single edge reels, 43 front scrapers, 16 edge scrapers, and 1 profiler. The center double hob cutter spacing is 90mm, and the single edge hob cutter spacing is 75mm. Among them, 4 side knives are higher than the diameter of the front shield, and each of the two outermost tracks has 2 side hob, which can reduce the number of side knives to change. In addition, the exchange of the hob and the tearing knife can be realized through the conversion seat to adapt to different formations.

Welded composite steel plate and surfacing grid are used on the cutter head panel; the outer ring beam welding is fully covered by composite steel plate + alloy protection knife to increase wear resistance. The cutter head is equipped with a hydraulic wear detection device to protect the cutter head body from being worn.

2.2. Main configuration parameters of shield machine

The model of the shield machine is CTE6450, the total length of the whole machine is about 86m, the total length of the main machine is 9600mm, and the total weight (main machine + rear support) is about 500T; the excavation diameter of the shield machine is φ6480mm, the speed of the cutter head is 0～3.7rpm; the maximum propulsion speed is about 80mm /min; maximum thrust 3991T, applicable to segment specifications (outer diameter/inner diameter-width/division) Φ6200/5500～1200/22.5°. The horizontal turning radius is 250m; the longitudinal climbing ability is ±50‰.

The shield adopts hydraulic drive; the shield body adopts passive hinge; the screw conveyor is in the form of a screw shaft, and the maximum slag discharge capacity is 420m3/h; the segment installation machine is a central rotary type; the VMT guiding system is adopted.

2.3. Key points of shield tunneling construction technology

The interval tunnel is excavated with earth pressure balance shield. The earth pressure balance is to use the soil cut by the shield machine to fill the sealing chamber and maintain proper earth pressure to balance the soil on the excavation surface, so as to achieve the excavation surface in front of the shield machine. purpose of support. Therefore, in the process of shield tunneling, it is necessary to adjust and set the soil pressure in time according to the geological difference, the thickness of the covering soil, the ground construction environment and the monitoring results of the surface uplift, to keep the advancing speed stable, control the amount of correction, and reduce the disturbance to the soil. , to create good conditions for segment assembly. Control the deviation between the construction axis and the design axis and the formation deformation within the allowable range.

2.4, parameter control

① According to the actual construction summary, the cutter head speed should be controlled within 1.0-1.2r/min, the cutter head torque should be kept within 1800KN.M, and the soil disturbance should be reduced to avoid burst Lake bottom soil. The tunneling speed is controlled within 40-60mm/min, and the total thrust is controlled within 17000KN to ensure uniform, safe and continuous passage of the shield machine. During the crossing period, the synchronous grouting shall be carried out at 5-6m ³ per ring. In the sand layer area, a water stop ring shall be made every ten rings at the position of the 6-7 ring of the shield tail. The synchronous grouting pressure shall be controlled at 2.5-3 bar, and the secondary grouting pressure shall be 0.5 Mpa～0.8Mpa.

②The boulder area is excavated. It has been proved that there are two boulder areas, one of the bedrock protrusions. During the crossing, the main parameters are controlled: the cutter head speed is 1.2r/min, the earth pressure is 1.1bar, the excavation speed is 10~30mm/min, the total The thrust is 17000KN, the cutter head torque is 2500KN.M, and the synchronous grouting volume is 5～6m ³ .

2.5. Risk control measures

①In order to avoid the gushing phenomenon when excavating through the Yundang Lake area, the screw machine double gate control is used to slow down the gushing pressure, and high molecular polymer is added to the screw machine and soil bin to improve the slag and increase the viscosity of the slag. And flow plasticity, reduce or avoid serious gushing. The shield machine is used with the secondary grouting equipment, and the secondary grouting sealing ring is carried out in time when the tenth ring of the shield tail is removed to prevent the groundwater from collusion behind the segment wall and flowing into the soil bin.

②According to the different burial depths of entering the lake, bottom of the lake, and exiting the lake, strictly control the pressure of each ring of soil silo to prevent the soil pressure from being too high and breaking the lake bottom.

③The sand layer and tunneling through the Yundang Lake must be passed quickly, stably and safely. Therefore, it is necessary to do a good job in the maintenance and repair work of the shield machine after the support (each vehicle, battery car, gantry crane, etc.) and the shield machine itself to ensure the shield machine. The mechanism quickly and stably excavates and passes through the area prone to spewing and when it passes through the Yundang Lake, avoiding abnormal downtime to the greatest extent.

④Strictly monitor the excavation situation of the screw excavator and the pressure change of the soil bin. If there is a spouting phenomenon, first close the upper and lower gates of the screw machine to cut off the water source to avoid a large amount of groundwater, quicksand or added mud. The high molecular polymer was injected into the screw machine and the soil bin, and the excavation was continued after thorough stirring and improvement.

⑤ Prepare polyurethane in the hole, connect the polyurethane injection pipeline to the screw conveyor improvement system, and inject polyurethane directly when the screw machine spews to control the spout;

⑥ Prepare the boat on the lake surface, and place emergency sandbags, water surface isolation belts and other emergency supplies on the boat in advance. During the crossing of Yundang Lake, special personnel will be on duty for 24-hour inspections. If roof caving occurs, place sandbags in the roof caving area in time to avoid the expansion of the area.

⑦Before the shield machine passes through, the geological exploration holes at the bottom of the lake are grouted and blocked one by one, so as to avoid the phenomenon of roof falling during the excavation, which will lead to the connection between the tunnel face and the bottom of the lake, and a large amount of lake water in the warehouse will cause the spiral machine to spout;

⑧If the groundwater on the front is too rich, the bentonite injected into the screw conveyor can be increased to facilitate the screw conveyor to form a soil plug effect. When the water influx is large, high molecular polymers can be injected to prevent gushing; Ensure that the muck is shipped out in time, and ensure continuous advancement during the passage through the Yundang Lake.

⑨Strictly control the pressure and volume of synchronous grouting and secondary grouting, control the synchronous grouting pressure within 0.25～0.3Mpa, make a double-liquid water stop ring every ten rings, and control the secondary grouting pressure within 0.8Mpa , to avoid water seepage at the shield tail due to excessive grouting pressure penetrating the lake bottom;

⑩ The muck improvement and foam system use high-quality grease and foam during the crossing of Yundang Lake.

To sum up, in the above-mentioned embodiments of the present invention, the shield construction method suitable for penetrating tidal lakes, by strengthening the unfavorable geology in the tidal lake area, enables the shield to be used in composite strata containing boulders, bedrock protrusions, medium sand, etc. The construction under the tidal lake area greatly improves the working environment, greatly reduces the construction risk of shield tunneling through the tidal lake, effectively prevents the risks of abnormal lake surface, sand and water gushing, and has a high degree of automation and overall construction safety quality. In addition, cofferdams are set up again in different areas during the excavation process to reduce the impact of tidal water level changes on the excavation process of the shield machine. At the same time, according to the law of tides, the pressure in the warehouse in front of the shield machine is adjusted to avoid the height of the warehouse opening at the bottom of the lake. The risk condition solves the technical problem of potential safety hazards in the prior art when the shield passes through the tidal lake in the reclamation area.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the patent of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (8)

1. A shield construction method suitable for passing through a tidal lake, the method comprising:

firstly, carrying out real-site survey on a site, determining the range of unfavorable geology in a tidal lake region, and marking stratums in the range as grouting stratums;

cofferdams are arranged in the grouting stratum in different areas to reduce the water level of the tidal lake, and grouting pipes are inserted in the cofferdams and used for injecting grout to reinforce the unfavorable geology in the tidal lake area;

after grouting is finished, starting the shield machine to carry out tunneling work, setting cofferdams again in different areas to reduce the influence of tide water level change on the tunneling process of the shield machine in the tunneling process, simultaneously adjusting the pressure in a front cabin of the shield according to the tide rule, increasing the pressure of a soil cabin when the tide rises, and reducing the pressure of the soil cabin when the tide falls.

2. The shield construction method suitable for going through a tidal lake according to claim 1, wherein the slurry comprises cement and water glass in a ratio of 1: 1.

3. The shield construction method suitable for downward crossing tidal lakes according to claim 1, wherein the number of grouting pipes in the cofferdam is not less than 3/m²。

4. The shield construction method suitable for downward crossing of tidal lakes of claim 1, wherein the grouting pipe is a PVC pipe.

5. The shield construction method suitable for downward crossing of tidal lakes according to claim 1, wherein the shield machine is an earth pressure balance shield and a spoke panel type cutter head is selected.

6. The shield construction method suitable for downward crossing of a tidal lake according to claim 5, wherein when the shield machine tunnels to outside of the tidal lake by 50m, the tunneling speed is reduced to increase the earth pressure.

7. The shield construction method suitable for downward-crossing tidal lakes as claimed in claim 5, wherein after the shield machine passes through, the back grouting work of the shield segment is performed, and the internal force change and the water leakage condition of the segment are monitored, and the grouting work is further performed.

8. The shield construction method suitable for downward traversing a tidal lake of claim 1, wherein the number of cofferdams in the grouting formation is at least 3.

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