A method for simulating an environment of a test field in situ for synchronous grouting of a shield tunnel

Abstract

The technical problem to be solved by the present application is to provide a shield tunnel synchronous grouting in-situ test field environment simulation method, a test box containing soil is arranged in the intermediate shaft, the shield tunneling machine carries out normal tunneling, segment assembly and synchronous grouting operation when passing through the test box, the stratum settlement deformation and the synchronous grouting effect are monitored through various measurement methods, and the method has high engineering practical value, provides a reference for similar engineering, and comprises a shield tunneling machine and a test box, the shield tunneling machine and the test box are placed in the intermediate shaft, and the test box is located between the cutter head of the shield tunneling machine and the pre-excavation surface; the top surface of the test box is open, circular openings larger than the outer diameter of the shield tunneling machine are arranged on the front and rear sides of the test box, and the synchronous grouting effect is judged by comprehensively considering the maximum settlement value of the soil, the uniformity of the water and soil pressure measurement value, and the grout injection form tested by the three-dimensional laser scanner and the geological radar detector.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shield construction, in particular to a method for simulating the environment of a shield tunnel synchronous grouting in-situ test field. BACKGROUND

[0002] The shield method has become one of the mainstream methods in the field of tunnel engineering due to its safety, high efficiency, high quality and environmental protection. During the shield tunneling process, the outer diameter of the cutter head of the shield machine is larger than the outer diameter of the lining segment, and over-excavation occurs during the excavation process. After the shield tail separates from the segment, an annular gap will appear between the segment and the stratum, which is the shield tail gap. If the shield tail gap is not treated in time, it will easily lead to an increase in water accumulation in the gap, causing segment leakage. The segment will deform and dislocate due to the lack of constraints under the action of the jack. In addition, the stratum deformation gradually increases, which will eventually lead to over-limit ground settlement, causing adverse effects on surrounding buildings in urban tunnel construction. In actual shield tunnel engineering, synchronous grouting technology is usually used to fill the shield tail gap.

[0003] Synchronous grouting is an important process during shield tunneling, which is crucial for controlling ground settlement and inhibiting surrounding rock deformation. Currently, synchronous grouting materials are mainly divided into single-liquid slurry and double-liquid slurry. Single-liquid slurry is mainly divided into single-liquid inert slurry and single-liquid hard (active) slurry. Currently, single-liquid hard (active) slurry composed of water, sand, cement, fly ash, etc. is widely used in China. Double-liquid slurry is pumped through two pipes, mixed in the shield tail grouting hole, and injected into the shield tail gap. A slurry is a cement-based material, and B slurry is usually a water glass material as a hardening agent. The chemical gel time of the mixed slurry is less than 60 seconds, and the strength is also high, which can effectively fill the shield tail and control ground settlement.

[0004] Currently, single-liquid slurry is mainly used for synchronous grouting in domestic shield tunnels. During construction, some segments will float, especially in rock strata, which indicates that the synchronous grouting slurry is not evenly filled, and the effect is not ideal. However, it is difficult to verify the effect of synchronous grouting after the completion of the underground concealed project. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a method for simulating the environment of a shield tunnel synchronous grouting in-situ test field. A test box filled with soil is set in the middle well. The shield machine performs normal tunneling, segment assembly, and synchronous grouting operations when passing through the test box. The stratum settlement deformation and synchronous grouting effect are monitored through various measurement methods, which has high engineering practical value and provides a reference for similar projects.

[0006] The present application is achieved by the following technical solutions:

[0007] A shield tunnel synchronous grouting in-situ test field environment simulation method, comprising a shield machine and a test box, the shield machine and the test box are placed in a middle shaft, and the test box is located between a cutter head of the shield machine and a pre-excavation surface;

[0008] The top surface of the test box is open, and the front and rear sides of the test box are provided with circular openings larger than the outer diameter of the shield machine;

[0009] The simulation method comprises the following steps:

[0010] (1) The original soil is filled in the test box, and a water and soil pressure gauge is buried in the original soil during the filling process;

[0011] (2) After the soil filling is completed, a settlement monitoring point is arranged on the surface of the test box;

[0012] (3) The shield machine starts to tunnel, and the shield machine passes through the test box according to the normal process of tunneling, segment assembly and synchronous grouting, and the water and soil pressure change data during the test are recorded by the water and soil pressure gauge, and the surface settlement value of the soil in the test box is recorded by the settlement monitoring point;

[0013] (4) When the shield machine passes through the entire test box and reaches the pre-excavation surface of the stratum, normal construction is started;

[0014] (5) The morphology and compactness of the synchronous grouting ring are detected by combining a geological radar detector and a three-dimensional laser scanner. The geological radar detector is placed inside the segment for detection when the test box is not removed, and the three-dimensional laser scanner scans the synchronous grouting layer directly outside the segment after the test box and the internal soil are removed;

[0015] (6) Finally, the synchronous grouting effect is judged by comprehensively considering the maximum settlement value of the soil, the uniformity of the water and soil pressure gauge value change, and the grout grouting morphology tested by the three-dimensional laser scanner and the geological radar detector.

[0016] Further, in step (3), the synchronous grouting of one ring of segments is used as the basis for different ring grouting processes, and the grouting amount, grouting pressure and grout type can be changed.

[0017] Further, a guide rail is arranged in the middle shaft, the guide rail extends into the test box, and the shield machine is matched with the guide rail.

[0018] The beneficial effects obtained by the present application compared with the prior art are as follows:

[0019] 1. The test box is placed in the middle shaft, and the soil is filled in the test box, so that the shield machine passes through the test box according to the normal process of tunneling, segment assembly and synchronous grouting;

[0020] The water and soil pressure meter buried in the test box can be used to study the change law of the soil and water pressure caused by the filling of the slurry in the shield tail gap during the synchronous grouting process; the wall back grouting cavity is detected by the geological radar detector and the slurry grouting form is detected by the three-dimensional laser scanner, so that the position of the grouting defect can be directly obtained and the reason can be analyzed; the surface settlement change law during the synchronous grouting process can be measured through the settlement monitoring point;

[0021] The synchronous grouting effect is judged by comprehensively considering the maximum settlement value of the soil, the uniformity of the water and soil pressure meter value change and the slurry grouting form tested by the three-dimensional laser scanner and the geological radar detector;

[0022] The synchronous grouting process of the shield tunnel is simulated, and the synchronous grouting effect can be verified through analysis of the test data, and reference guidance can be provided for similar projects;

[0023] 2、The scheme idea of the simulation method is simple, the test box device manufacturing process is simple, the operation process is not complex, and the test box device can be repeatedly used for many times;

[0024] 3、The simulation method can discuss various tunneling parameters, take a ring segment as a discussion benchmark, and can discuss various problems by changing the slurry type, grouting amount, grouting pressure and parameters of the shield tunneling speed. DETAILED DESCRIPTION

[0025] Figure 1 The test box and shield machine installation schematic diagram before the simulation method is carried out;

[0026] Figure 2 The internal structure schematic diagram of the test box before filling the stratum soil before the test;

[0027] Figure 3 The internal structure schematic diagram of the test box after the test;

[0028] Figure 4 The stratum settlement monitoring schematic diagram.

[0029] In the figure: 1, guide rail, 2, shield machine, 3, negative ring segment, 4, test box, 5, stratum soil. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0031] In the description of the invention, it should be understood that the terms "front", "back", "up", "down", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation on the invention.

[0032] Taking a common urban subway shield tunnel with a diameter of 6 m and a buried depth of 20 m as an example, the preparation of related devices is carried out before the in-situ test field environment simulation method of the shield tunnel synchronous grouting according to the present application.

[0033] As shown in Figures 1-4 First, a guide rail 1 is arranged in the intermediate well, and a 6 m specification shield machine 2 and its related components are assembled and placed on the guide rail 1, and the negative ring segment 3, the synchronous grouting pipe and the slurry and other conventional components are prepared. Then, the test box 4 is assembled in the intermediate well, and the test box 4 is located between the cutter head of the shield machine 2 and the pre-excavation surface. The top surface of the test box 4 is open, and the size is 10 m (length) x 18 m (width) x 10 m (height). Circular openings slightly larger than the outer diameter of the shield machine 2 are machined on the front and rear sides of the test box 4, and the guide rail 1 extends into the test box 4, so as to ensure that the shield machine 2 can walk in a specific direction.

[0034] The in-situ test field environment simulation method of the shield tunnel synchronous grouting according to the present application comprises the following steps:

[0035] (1) The original stratum soil 5 is filled in layers in the test box 4, and during the filling process, the water and soil pressure gauges (including a soil pressure gauge with a range of 0.5 Mpa and a water pressure gauge) are buried in the stratum soil 5 according to the designed position to record the changes of water and soil pressure during the test;

[0036] (2) After the filling is completed, settlement monitoring points are provided on the surface of the test box 4, and a level instrument is used to monitor the change of stratum settlement; at the same time, a three-dimensional laser scanner and a geological radar detector are prepared to detect the grouting effect after the shield machine 2 passes through the test box 4. The centers of the test box 4, the shield machine 2 and the pre-excavation surface are calibrated on the same straight line to prevent the two from deviating at the beginning of the test, and the preparation work for the test is completed;

[0037] (3) The shield machine 2 starts to dig, and controls the shield machine 2 to dig forward at a normal digging speed, when passing through the soil inside the test box 4, the soil is excavated by the cutter head, and when excavated to a certain distance, segment support assembly, synchronous grouting and other operations are carried out, until the shield machine 2 passes through the prototype test box 4;

[0038] During the test, based on synchronous grouting of a segment, different grouting can change grouting amount (such as grouting filling coefficient 1.1, 1.2, 1.4), grouting pressure (0.2Mpa, 0.3Mpa, 0.4Mpa), slurry type (such as inert slurry, single liquid slurry, double liquid slurry) and the like, so as to form different grouting effects.

[0039] By setting stratum settlement monitoring points on the surface of the original stratum soil 5 in the test box 4 before the test, the stratum settlement change during the test is recorded. The soil and water pressure changes caused by the slurry filling the shield tail gap during grouting are recorded by the buried soil and water pressure gauges;

[0040] (4) When the shield machine 2 passes through the entire test box 4 and reaches the pre-excavated surface of the stratum, normal construction is started;

[0041] (5) When the test box 4 and the internal soil are not removed, the geological radar detector is placed inside the segment to detect the wall back grouting cavity and the density; after the test box 4 and the internal soil are removed, the three-dimensional laser scanner is used to scan the synchronous grouting layer directly on the outside of the segment;

[0042] (6) Finally, the synchronous grouting effect is evaluated by comprehensively considering the maximum settlement value of the soil, the uniformity of the soil and water pressure measurement value, and the slurry grouting form tested by the three-dimensional laser scanner and the geological radar detector.

[0043] The evaluation criteria for the grouting effect after the shield tunnel synchronous grouting in-situ test field environment simulation method are as follows:

[0044] The maximum ground settlement value is required to be less than or equal to 10mm, the water and soil pressure distribution is required to be uniform, and the defect depth of the synchronous grouting ring should be less than 2cm, accounting for more than 90%.

[0045] The simulation test is carried out by the above-mentioned shield tunnel synchronous grouting in-situ test field environment simulation method, which has simple test scheme ideas, simple test device manufacturing process and simple operation process, and can be repeatedly used for many times;

[0046] The test method can explore various tunneling parameters, taking a segment as the discussion benchmark, such as changing the slurry type, grouting amount, grouting pressure and parameters of the shield tunneling speed, which can explore various problems; not only can the soil and water pressure change law caused by the slurry filling the shield tail gap during synchronous grouting be studied, but also the position of the grouting defect can be directly obtained and the reason can be analyzed; the ground settlement change law during synchronous grouting can also be obtained; the test scheme truly simulates the process of synchronous grouting of the shield tunnel, the synchronous grouting effect can be verified through test data analysis, and reference guidance can be provided for similar projects.

Claims

1. A method for simulating the environment of a field test site for in-situ testing of synchronous grouting of a shield tunnel, characterized in that, The shield machine and the test box are placed in the intermediate shaft, and the test box is located between the cutter head of the shield machine and the pre-excavation surface; The top surface of the test box is open, and the front and rear sides of the test box are provided with circular openings larger than the outer diameter of the shield machine; The simulation method comprises the following steps: (1) The undisturbed stratum soil is filled in the test box, and a water and soil pressure gauge is embedded in the undisturbed stratum soil during the filling process; (2) After the filling is completed, a settlement monitoring point is arranged on the surface of the test box; (3) The shield machine starts to excavate, and the shield machine passes through the test box according to the normal process of excavation, segment assembly and synchronous grouting. In step (3), the grouting amount, grouting pressure and grout type can be changed during the grouting process of different rings based on the synchronous grouting of one ring of segments during the test process; During the process that the shield machine passes through the test box, the water and soil pressure change data during the test process are recorded by the water and soil pressure gauge, and the surface settlement value of the soil in the test box is recorded by the settlement monitoring point; (4) After the shield machine passes through the entire test box and reaches the pre-excavation surface of the stratum, normal construction is started; (5) The form and compactness of the synchronous grouting ring are detected by combining a geological radar detector and a three-dimensional laser scanner; The geological radar detector is placed inside the segment for detection when the test box is not removed, and the three-dimensional laser scanner scans the synchronous grouting layer directly outside the segment after the test box and the internal soil are removed; (6) Finally, the synchronous grouting effect is evaluated by comprehensively considering the maximum settlement value of the soil, the uniformity of the water and soil pressure gauge value change, and the grout grouting form tested by the three-dimensional laser scanner and the geological radar detector.

2. The method according to claim 1, wherein, A guide rail is arranged in the intermediate shaft, the guide rail extends into the test box, and the shield machine is matched with the guide rail.

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