CN107742032B - A Calculation Method for Soil Deformation Caused by Ground Access Shield Excavation Under Shallow Soil Covering Conditions - Google Patents

Abstract

The invention relates to a method for calculating soil deformation caused by excavation of a ground access type shield under shallow overlying soil conditions, comprising the following steps: (1) parameter calculation: tanβ parameter calculation, g parameter calculation; (2) soil deformation Based on the newly established convergence model of the tunnel excavation section in which the tunnel floats up to the top of the soil boundary, using the stochastic medium theory, a micro-unit is taken, and the three directions of x, y, and z caused by the construction of the ground access shield tunnel are derived The formula for calculating soil deformation. The beneficial effect of the present invention is that: the present invention deeply studies the convergence model of the excavation section of the shallow-covered ground access type shield, and considers the buoyancy of the tunnel after grouting caused by the shallow cover and the angle α between the shield axis and the horizontal plane, based on random The medium theory, the deduced soil deformation calculation formula, and the use of Matlab can quickly calculate the vertical deformation and horizontal deformation of the soil in actual engineering.

Description

A method for soil deformation caused by ground access shield excavation under shallow overlying soil conditions calculation method

technical field

The invention relates to a calculation method for calculating the soil deformation of shallow-covered ground access shield tunneling caused by soil loss by using random medium theory and a novel tunnel excavation section convergence model. It belongs to the technical field of underground engineering.

Background technique

The construction depth of the ground access shield method is relatively shallow, especially the disturbance of the shallow section of the covering soil is relatively large, which may cause damage to adjacent underground pipelines and buildings, posing serious safety hazards. Existing calculation methods for soil deformation caused by ground access shield tunneling method only consider the working condition of upward excavation but not downward excavation, and do not consider the influence of tunnel buoyancy under the condition of shallow overlying soil, only the vertical deformation of the soil can be calculated. Calculation, the horizontal soil deformation cannot be calculated, and it is different from the actual situation.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a reasonable calculation method for soil deformation caused by ground access shield excavation under shallow overlying soil conditions.

The calculation method for soil deformation caused by ground access shield excavation under shallow overlying soil conditions includes the following steps:

S1. Parameter calculation

S1.1tanβ parameter calculation

According to the formula:

In the formula: tanβ is the tangent value of the main influence angle of the soil layer around the tunnel; β is the main influence angle of the soil layer around the tunnel; k is the width parameter of the surface settlement trough; H is the buried depth of the shield tunnel axis;

The buried depth formula of shield tunnel axis:

H＝h-tanα (2)

In the formula: h is the buried depth of the initial tunnel axis;

Simultaneous formula (1), (2) get:

S1.2g parameter calculation

g is the equivalent soil loss parameter, ε is the maximum soil loss rate, R is the outer radius of the shield machine, and the relationship between g and the soil loss rate ε uses the formula:

The purpose of this step is to determine the input parameters for the calculation of soil deformation;

S2. Calculation of soil deformation

Based on the newly established tunnel excavation section convergence model in which the tunnel floats up to the top of the soil boundary; R is the outer radius of the shield machine, and g is the equivalent soil loss parameter; using the stochastic medium theory, a micro-unit is taken to derive the ground access Calculation formulas for soil deformation in x, y, and z directions caused by shield tunneling construction;

Calculation formula for horizontal deformation of soil along the direction of excavation:

The horizontal deformation formula of the soil perpendicular to the tunnel:

Calculation formula for vertical deformation of soil mass:

In the formula: β is the main influence angle of the soil layer around the tunnel; H is the buried depth of the shield tunnel axis; the upper and lower limits of the triple integral are: a=H+R, b=HR, e=HR, f=H+Rg,

The beneficial effects of the present invention are: this patent has deeply studied the convergence model of the excavation section of the shallow overburden ground access type shield, considering the tunnel uplift after grouting caused by the shallow overburden and the angle α between the shield axis and the horizontal plane, based on random The medium theory, the derived soil deformation calculation formula, can quickly calculate the vertical deformation and horizontal deformation of the soil in actual engineering by using Matlab. Through the theoretical formula of this patent, the soil deformation in the construction of the ground access shield under the actual shallow overlying soil condition is predicted, which has the function of preventing and guiding the project, and provides a basis for the construction of the ground access type shield under the shallow overlying soil condition in the future. Provide a theoretical basis for research on the impact on the surrounding environment.

Description of drawings

Figure 1 is a schematic diagram of the mechanical model;

Fig. 2 is the convergence mode of the excavation section of the ground access type shield machine;

Figure 3 is a schematic diagram of the excavation unit;

Figure 4 is the longitudinal surface subsidence curve of the 60th ring measuring point;

Figure 5 is the lateral surface subsidence curve of the 33rd ring measuring point;

Fig. 6 is the soil horizontal deformation curve along the longitudinal direction of the 65th ring measuring point;

Figure 7 is the horizontal deformation curve of the soil along the transverse direction at the 65th ring measuring point.

Detailed ways

The present invention will be further described below in conjunction with the examples. The description of the following examples is provided only to aid the understanding of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

This patent establishes a tunnel excavation section convergence model in which the tunnel floats up to the top of the soil boundary, and based on the random medium theory, establishes a calculation method for soil deformation caused by soil loss during the construction of shallow-covered ground access shield tunnels, which can effectively predict the ground Soil deformation in the shallow overburden section (≤0.5 times the diameter of the external machine of the shield) during the construction of the access shield method. The mechanical calculation model of the ground access shield is shown in Fig. 1.

In the figure, x is the horizontal distance from the excavation surface, and the excavation direction is positive; y is the horizontal horizontal distance from the axis; z is the vertical distance from the ground, and the downward is positive; α is the gap between the shield axis and the horizontal plane. Angle (up is a positive value, down is a negative value).

This patent provides a calculation method for soil deformation caused by ground access shield excavation under shallow overlying soil conditions, including the following two steps:

1. Parameter calculation

1.1 Calculation of tanβ parameter

According to the formula:

In the formula: tanβ is the tangent value of the main influence angle of the soil layer around the tunnel; β is the main influence angle of the soil layer around the tunnel; k is the width parameter of the surface settlement trough; H is the buried depth of the shield tunnel axis.

The buried depth formula of shield tunnel axis:

H＝h-tanα (2)

In the formula: h is the buried depth of the initial tunnel axis.

Simultaneous formula (1), (2) get:

1.2g parameter calculation

g is the equivalent soil loss parameter, ε is the maximum soil loss rate, R is the outer radius of the shield machine, and the relationship between g and the soil loss rate ε uses the formula:

The purpose of this step is to determine the input parameters for the calculation of soil deformation.

2. Calculation of soil deformation

The convergence model of the tunnel excavation section based on the newly established tunnel floating to the top of the soil boundary is shown in Fig. 2. In the figure, R is the outer radius of the shield machine, and g is the equivalent soil loss parameter. Using the stochastic medium theory, take a micro-unit, as shown in Figure 3, and derive the calculation formulas for the soil deformation in the three directions of x, y, and z caused by the construction of the ground access shield tunnel.

Calculation formula for horizontal deformation of soil along the direction of excavation (longitudinal):

The horizontal deformation formula of the soil in the direction perpendicular to the tunnel (horizontal direction):

Calculation formula for vertical deformation of soil mass:

In the formula: β is the main influence angle of the soil layer around the tunnel; H is the buried depth of the shield tunnel axis; the upper and lower limits of the triple integral are: a=H+R, b=HR, e=HR, f=H+Rg,

The above formulas are compiled into corresponding computer programs using MATLAB, and the relevant calculation parameters can be input to easily calculate the soil deformation around the tunnel caused by the loss of soil during the construction of the ground access shield.

This patent is based on the ground access section project of Nanjing Airport Line Moling Station to Jiangjun Road Station in the article "Study on Structural Deformation Characteristics and Control of Ground Access Shield Tunnel" by Wu Huiming, and adopts single-line ground access shield tunneling method for construction.

Implementation example 1:

Parameter value: The thickness of the covering soil layer at the measuring point of the 60th ring of the tunnel is 0.5D=3.1m. Calculation parameter values: h＝6.2m, D＝6.2m, ε＝0.096％, according to Han Xuan’s "Study on Practical Methods for Stratum Displacement and Building Deformation Prediction Caused by Tunnel Construction" about the surface settlement trough width parameter k Value research, this example takes k=0.50, α=-2.6°.

Step 1: Calculate the value of the parameter. When calculating the surface settlement according to the value of the parameter, the 60th ring measuring point of the tunnel along the excavation direction tanβ is the tangent value of the main influence angle of the soil layer around the tunnel according to the formula (3) is calculated as follows Value relational formula:

When calculating the surface settlement according to the value of the parameter, the equivalent soil loss parameter g along the excavation direction of the 60th ring measuring point of the tunnel is calculated according to the formula (4)

Step 2: Substituting the parameters calculated in step 1 and the given basic parameters into formula (7) and using MATLAB to compile a corresponding computer program, input the calculation coordinates, record and calculate the surface subsidence value, and enter it into an Excel table.

Step 3: Use the calculation data calculated in step 2 and DataDig352 software to extract the data from Teng Li's article "Ground Access Shield Tunneling Technology (GPST) Construction Deformation Monitoring and Analysis Research" that contains the corresponding data graph, and put it in an Excel table Draw a graph inside.

Step 4: Analyze the graph and draw conclusions. As shown in Figure 4: (1) When the shield tunneling, the soil loss mainly caused the surface settlement, which was concentrated behind the excavation face, and the settlement value was the largest (4.2mm) at about 25m behind the excavation face; (2 ) The calculation results of this paper are in good agreement with the finite element simulation values and actual measurement data of the longitudinal surface settlement method in Teng Li's "Ground Access Shield Tunneling Technology (GPST) Construction Deformation Monitoring and Analysis Research", which shows that the new model and calculation of this paper The method has certain reliability; (3) The measured settlement value behind the excavation face tends to decrease obviously. Since the method in this paper does not consider the shield shell friction and additional grouting pressure, there is a certain deviation from the measured data.

Implementation example 2:

Parameter value: The thickness of the covering soil layer at the measuring point of the 33rd ring of the tunnel is 0.3D=1.86m. Calculation parameter values: h=4.96m, D=6.2m, ε=0.107%, according to the selection of the surface settlement trough width parameter k in the article "Research on the Practical Method of Stratum Displacement and Building Deformation Prediction Caused by Tunnel Construction" by Han Xuan Value research, this example takes k=0.50, α=-1.2°.

The implementation steps are the same as the implementation example 1, and steps 1 to 3 are carried out according to the corresponding working conditions and parameter values. Only step 4 is introduced.

Step 4: Analyze the graph and draw conclusions. As shown in Figure 5: (1) The calculation results of the method in this paper are very consistent with the finite element simulation value and actual measurement data of the lateral surface settlement of Zhao Xinwei's "Shield Fast Crossing Method for Ultra-shallow and Negative Covered Soil Tunnel Construction Prediction Analysis". The maximum value calculated by the method in this paper is closer to the measured value than the finite element settlement simulation value in Zhao Xinwei's "Construction Prediction and Analysis of Super Shallow Covered Soil and Negative Covered Soil Tunnel with Shield Fast Crossing Method", which shows that the theoretical solution in this paper is reliable; (2) the lateral surface The settlement influence range is about 8m from both sides of the tunnel axis, and the maximum settlement value is about 5mm; (3) Since the method in this paper only considers soil loss, there is no surface uplift in the calculation results. Both the actual measurement and the finite element simulation show a slight uplift at a position about 8m away from the tunnel axis.

Implementation example 3:

Parameter value: the thickness of the covering soil layer at the 65th ring measuring point of the tunnel is 0.5D=3.1m. Calculation parameter values: h=6.2m, D=6.2m, ε=0.35%, according to the value of the surface settlement trough width parameter k in Han Xuan's "Research on Practical Methods for Stratum Displacement and Building Deformation Prediction Caused by Tunnel Construction" For research, this example takes k=0.50, α=-2.6°.

Implementation steps are the same as implementation example 2.

Step 4: Analyze the graph and draw conclusions. As shown in Figure 6: (1) The calculation results of the method in this paper are basically consistent with the measured data in Wu Huiming's "Research on the Structural Deformation Characteristics and Control of Ground Access Shield Tunnel", which shows the reliability of the theoretical solution in this paper; (2) The horizontal deformation of the soil is negative, that is, it moves toward the tail of the shield, which is due to the loss of the soil; (3) The horizontal deformation of the soil along the longitudinal direction has a greater influence on the upper part of the tunnel axis, and the maximum deformation value in actual engineering is controlled by Better, the maximum value is less than 3mm.

As shown in Figure 7: (1) The calculation results of the method in this paper are basically consistent with the measured data in Wu Huiming's "Research on the Structural Deformation Characteristics and Control of Ground Access Shield Tunnel", which shows that the theoretical solution of this paper is reliable; (2) In the vertical depth At the position near 4m, the direction of horizontal deformation has changed. The soil mass moves outward at 0-4m, and moves toward the tunnel below 4m; Large, the maximum deformation value is well controlled in actual engineering, and the lateral horizontal deformation value of the soil ranges from -4mm to 3mm.

Claims (1)

1. one kind exists for soil deformation calculation method caused by ground suction/discharge type shield tunneling under shallow earthing operating condition, feature In including the following steps:

S1. parameter calculates

S1.1tan β parameter calculates

According to formula:

In formula: tan β is the main influence tangent of an angle value of tunnel perimeter soil layer；β is the main influence angle of tunnel perimeter soil layer；k For surface settlement trough width parameter；H is shield tunnel axis buried depth；

Shield tunnel axis buried depth formula:

H=h-tan α (2)

In formula: h is original tunnel axis buried depth；

Joint type (1), (2) obtain:

S1.2g parameter calculates

G is equivalent ground loss parameter, and ε is maximum ground loss rate, and R is shield machine outer radius, between g and ground loss rate ε Relationship, using formula:

The purpose of this step is to determine input parameter for the calculating of soil deformation；

S2. the calculating of soil deformation

Model is restrained based on the tunnel excavation section at the top of newly-established tunnel upward floating to soil boundary；R is shield machine outer radius, G is equivalent ground loss parameter；Using stochastic medium theory, a micro unit is taken, ground suction/discharge type shield tunnel is derived by and applies Work causes x, the soil deformation calculation formula in tri- directions y, z；

Along the horizontal deformation of soil body at worked calculation formula of tunneling direction:

With the horizontal deformation of soil body at worked formula of tunnel vertical direction:

The vertical vertical deformation calculation formula of the soil body:

In formula: β is the main influence angle of tunnel perimeter soil layer；H is shield tunnel axis buried depth；Triple integral bound difference Are as follows: a=H+R, b=H-R, e=H-R, f=H+R-g,