A method for predicting the compression of overlying strata caused by shield machine construction disturbance

Abstract

The present invention relates to a method for predicting the amount of compression of overlying strata caused by shield machine construction disturbance. The method works by arguing that during shield construction, the shield machine disturbs the surrounding strata, causing soil particles to shift relative to each other, generating internal stress and displacement. This compresses the internal pore water, increasing water pressure. The internal stress generated by the soil particles is equal to the water pressure increase. Based on this, a dynamic triaxial test is used to determine the peak water pressure increase and the disturbance elastic modulus. The deformation of the overlying strata caused by the shield machine construction disturbance is further calculated. This method has the advantages of simple structure, strong process flow, and reliable results.

Description

Technical Field

[0001] The present invention relates to the field of tunnel construction, and in particular to a method for predicting the compression of overlying strata caused by disturbance during shield machine construction. Background Art

[0002] Shield tunneling is a common method for tunnel construction, characterized by high speed, high safety, and relatively minimal impact on the surrounding environment. However, during construction, it also causes a certain degree of vibration in the surrounding strata, disturbing the overlying soil and causing deformation. Excessive deformation can affect the safety of surface and underground structures. Currently, the deformation of the overlying soil caused by disturbance is mostly measured by deploying monitoring points. This method is time-consuming and labor-intensive, and there is no reliable theoretical basis for prediction. In view of this, the present invention proposes a method for predicting the deformation of the overlying strata caused by shield machine construction. This method has the advantages of simple structure, strong process flow, and reliable results. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for predicting the compression of overlying strata caused by shield machine construction disturbance, which has the advantages of simple structure, strong process and reliable results.

[0004] To achieve the above object, the technical solution of the present invention is: a method for predicting the compression of overlying strata caused by shield machine construction disturbance, comprising the following steps:

[0005] (1) Determine the shield machine's single thrust working time T;

[0006] (2) Determine the groundwater depth H w ;

[0007] (3) Determine the thickness of the soil covering the shield machine cutterhead H s ;

[0008] (4) Determine the weight of the soil above the groundwater level γ0 and the weight of the soil below the groundwater level γ sat ;

[0009] (5) Determine the vibration signal indicators of the ground surface and the ground at the cutterhead of the shield machine during the construction process;

[0010] (6) Determine the peak water pressure increase U1 of the soil at the cutterhead;

[0011] (7) Determine the peak water pressure increase U at a depth z below the ground z ;

[0012] (8) Determine the disturbed elastic modulus E of the soil;

[0013] (9) Determine the deformation S of the overlying strata caused by the shield machine construction disturbance.

[0014] Compared with the existing technology, the present invention has the following beneficial effects: the working principle of the present invention is that when the shield machine is under construction, it disturbs the surrounding strata, causing soil particles to shift relative to each other, generating internal stress and displacement, compressing the internal pore water, and causing water pressure to increase. The internal stress generated by the soil particles is equal to the water pressure growth value. Based on this, the dynamic triaxial test is used to obtain the water pressure growth peak value and the disturbance elastic modulus, and the deformation of the overlying strata caused by the shield machine construction disturbance is further calculated. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is described in detail below.

[0016] The present invention provides a method for predicting the compression of overlying strata caused by shield machine construction disturbance, comprising the following steps:

[0017] (1) Determine the shield machine's single thrust working time T.

[0018] Determine the working time T according to the shield machine construction plan.

[0019] (2) Determine the groundwater depth H w .

[0020] According to the geological survey report, determine the groundwater level depth H w .

[0021] (3) Determine the thickness of the soil covering the shield machine cutterhead H s .

[0022] According to the shield machine construction plan, determine the thickness of the soil covering the cutterhead H. s .

[0023] (4) Determine the weight of the soil above the groundwater level γ0 and the weight of the soil below the groundwater level γ sat .

[0024] Using a geological drill, typical soil samples were taken above and below the groundwater level. After being transported back to the laboratory, their densities were tested using the ring knife method, and then multiplied by the acceleration of gravity to obtain their corresponding weights.

[0025] (5) Determine the vibration signal indicators of the ground surface and the ground at the cutterhead of the shield machine during the construction process of the shield machine.

[0026] Vibration sensors and signal acquisition devices are deployed on the ground directly above the shield machine's cutterhead and in the soil at the cutterhead. These sensors collect vibration signals generated by the ground and the soil at the cutterhead during construction. Vibration signal processing software is then used to determine the dominant vibration frequency and amplitude of each. The dominant vibration frequency at the ground and the soil at the cutterhead are equal, both denoted by f. The amplitude at the ground is denoted by A1, and the amplitude of the soil at the cutterhead is denoted by A2.

[0027] (6) Determine the peak water pressure increase U1 of the soil at the cutterhead.

[0028] Typical undisturbed soil samples obtained by drilling were transported back to the laboratory for dynamic triaxial tests. The applied vibration frequency was f, the amplitude was A2, and the confining pressure was σ3, where:

[0029] σ3=K0σ2

[0030] σ2=γ0H w +(γ sat -10)(H s -H w )

[0031] Among them, K0 is 0.6.

[0032] The peak value of water pressure increase during the test is measured and expressed as U1.

[0033] (7) Determine the peak water pressure increase U at a depth z below the ground z .

[0034]

[0035] Among them, z is the independent variable, indicating the depth.

[0036] (8) Determine the disturbed elastic modulus E of the soil.

[0037] The second dynamic triaxial test was carried out using the original soil sample retrieved from the site. The applied vibration frequency was f and the amplitude was A.

[0038] A=0.5(A1+A2)

[0039] The confining pressure is σ,

[0040] σ=0.5σ2

[0041] Test the maximum axial deformation Δl, and then calculate the disturbance elastic modulus E,

[0042]

[0043] Where l is the height of the original test soil sample, which is measured during the test.

[0044] (9) Determine the deformation S of the overlying strata caused by the shield machine construction disturbance.

[0045]

[0046] Among them, α is the empirical correction coefficient, which is taken as 1.25; β is the equivalent pressure coefficient, which is taken as 0.75.

[0047] Implementation Cases

[0048] A city uses a shield machine method to construct a subway, which passes through a main urban road in the city. The overlying geological conditions are poor, mainly consisting of weathered granite residual soil. In order to determine the deformation of the overlying strata induced by the shield machine construction disturbance, the method of the present invention is used for prediction.

[0049] According to the shield machine construction plan, the shield machine single advance working time T is determined to be 2h. According to the geological survey report, the groundwater level depth H is determined. w According to the shield machine construction plan, the thickness of the soil covering the cutterhead is determined as H. s Using a geological drill, typical soil samples were taken above and below the groundwater level. After being transported back to the laboratory, their densities were tested using the ring knife method. The density of the soil above the groundwater level was then multiplied by the acceleration of gravity, and the weight γ0 of the soil above the groundwater level was 18.3 kN / m 3 , the density of soil below the groundwater level γ sat 19.4kN / m 3 Vibration sensors and signal acquisition devices were deployed on the ground directly above the shield machine cutterhead and in the soil at the cutterhead. The vibration signals generated by the ground and the soil at the cutterhead during the shield machine construction process were collected. Vibration signal processing software was then used to determine the dominant vibration frequency and amplitude of both. The dominant vibration frequency f of the ground and the soil at the cutterhead was 26 Hz, the amplitude A1 of the ground was 0.17 mm, and the amplitude A2 of the soil at the cutterhead was 3.93 mm.

[0050] Typical undisturbed soil samples obtained by drilling were transported back to the laboratory for dynamic triaxial testing. The applied vibration frequency was 26 Hz, the amplitude was 3.93 mm, and the confining pressure was σ3 of 401.78 kPa. During the test, the peak value U1 of the water pressure increase was 85.2 kPa.

[0051] The water pressure increase peak value U at the depth z below the ground is further determined. z , denoted as U z=3.33z. A second dynamic triaxial test was conducted using undisturbed soil samples retrieved from the site. The applied vibration frequency was 26 Hz, the amplitude A was 2.05 mm, and the confining pressure σ was 334.82 kPa. In the dynamic triaxial test, the height l of the undisturbed test soil sample was 10 cm, and the maximum axial deformation Δl was 0.27 cm. The disturbance elastic modulus E was calculated to be 12400.7 kPa. The deformation S of the overlying stratum caused by the shield machine construction was determined to be 0.08 m.

[0052] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions and effects do not exceed the scope of the technical solution of the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A method for predicting the compression of overlying strata caused by shield machine construction disturbance, characterized in that: The steps include: (1) Determine the shield machine's single thrust working time T; (2) Determine the groundwater depth H w ; (3) Determine the thickness of the soil covering the shield machine cutterhead H s ; (4) Determine the weight of the soil above the groundwater level γ0 and the weight of the soil below the groundwater level γ sat ; (5) Determine the vibration signal indicators of the ground surface and the ground at the cutterhead of the shield machine during the construction process; (6) Determine the peak water pressure increase U1 of the soil at the cutterhead; (7) Determine the peak water pressure increase U at a depth z below the ground z ; (8) Determine the disturbed elastic modulus E of the soil; (9) Determine the deformation S of the overlying strata caused by the shield machine construction disturbance; In step (6), the method for determining the water pressure increase peak value U1 of the soil at the cutterhead is as follows: Typical undisturbed soil samples obtained by drilling were transported back to the laboratory for dynamic triaxial tests. The applied vibration frequency was f, the amplitude was A2, and the confining pressure was σ3, where: σ3=K0σ2 σ2=γ0H w +(c sat -10)(H s -H w ) In the formula, K0 is 0.6; The peak value of water pressure increase during the test is measured and expressed as U1; In step (7), the water pressure growth peak value U at the depth z below the ground is z The calculation formula is as follows: Among them, z is the independent variable, indicating depth; In step (8), the method for determining the disturbed elastic modulus E of the soil is as follows: The second dynamic triaxial test was carried out using the original soil sample retrieved from the site. The applied vibration frequency was f and the amplitude was A. A=0.5(A1+A2) The confining pressure is σ, σ=0.5σ2 Test the maximum axial deformation Δl, and then calculate the disturbance elastic modulus E, Where, l is the height of the original test soil sample, which is measured during the test; In step (9), the calculation formula for the deformation S of the overlying stratum caused by the shield machine construction disturbance is as follows: Among them, α is the empirical correction coefficient, which is taken as 1.25; β is the equivalent pressure coefficient, which is taken as 0.

75.

2. The method for predicting the amount of overlying strata compression caused by shield machine construction disturbance according to claim 1, characterized in that: In step (1), the method for determining the working time of a single advancement of the shield machine is: determining the working time T according to the shield machine construction plan.

3. The method for predicting the compression of overlying strata caused by shield machine construction disturbance according to claim 1, characterized in that: In step (2), determine the groundwater level depth H w The method is: According to the geological survey report, determine the groundwater level depth H w .

4. The method for predicting the compression of overlying strata caused by shield machine construction disturbance according to claim 1, characterized in that: In step (3), determine the thickness of the soil covering the shield machine cutterhead H s The method is: according to the shield machine construction plan, determine the thickness of the soil covering the cutter head H s .

5. The method for predicting the compression of overlying strata caused by shield machine construction disturbance according to claim 1, characterized in that: In step (4), the weight of the soil above the groundwater level γ0 and the weight of the soil below the groundwater level γ sat The method is: use a geological drill to take typical soil samples above and below the groundwater level respectively, transport them back to the laboratory and use the ring knife method to test their density respectively, and then multiply them by the acceleration of gravity to obtain the corresponding weight of the two.

6. The method for predicting the compression of overlying strata caused by shield machine construction disturbance according to claim 1, characterized in that: In step (5), the method for determining the vibration signal indicators of the ground surface and the ground at the cutterhead of the shield machine during the construction process of the shield machine is as follows: a vibration sensor and a signal acquisition instrument are arranged at the ground position directly above the cutterhead of the shield machine and the soil position at the cutterhead, and the vibration signals generated on the ground and the vibration signals generated by the soil at the cutterhead during the construction of the shield machine are collected. The vibration signal processing software is further used to obtain the main vibration frequency and amplitude of the two; wherein the main vibration frequency at the ground is equal to the main vibration frequency of the soil at the cutterhead, both of which are expressed as f, the amplitude at the ground is expressed as A1, and the amplitude of the soil at the cutterhead is expressed as A2.

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