Seabed pipe jacking construction vertical jacking force prediction method based on correction shear theory

Abstract

The invention discloses a seabed pipe jacking construction vertical jacking force prediction method based on a correction shear theory, and belongs to the technical field of underground tunnel engineering. The prediction method comprises the steps of analyzing components of jacking force F in vertical jacking method construction, determining a fracture angle alpha ', correcting an expression of the fracture angle alpha' according to actually measured data, calculating geometric parameters of a soil body in a shear failure surface, calculating a head-on resistance Fh value, calculating a pipe wall friction resistance Ff value and calculating the jacking force F value. An expression that the fracture angle changes along with the pushing distance of the jacking pipe is deduced by combining an existing soil body shear failure theory and a measured data inverse analysis method, so that the dynamic change of the soil body form in a shear failure surface and the head-on resistance in the whole construction process of the vertical jacking method can be accurately reflected; different construction conditions are considered in calculation of the frictional resistance of the pipe wall; the self weight of the jacking pipe and the water pressure above the jacking pipe are determined by combining the shear failure theory, and the jacking force of the whole construction process of the vertical jacking method can be predicted more accurately.

Description

Technical Field

[0001] The invention belongs to the technical field of underground tunnel engineering and relates to a method for predicting vertical lifting force of submarine pipe jacking construction based on modified shear theory. Background Art

[0002] Drainage tunnels are important supporting buildings for large nuclear power plants in coastal areas. The vertical jacking method is widely used in the construction of drainage head structures of drainage tunnels due to its advantages such as short construction period, small impact on the environment and high economic benefits.

[0003] The dynamic change law of soil resistance and lifting force during the whole process of vertical jacking construction and its prediction method not only involve the design of the lifting pipe structure and the tunnel bottom reinforcement design in the design stage, but also involve the formulation of parameters such as lifting reaction force, lifting speed, and drag reduction mud in the construction plan. At present, the theoretical calculation of the lifting force of the vertical jacking method mainly includes the following three methods: (1) Foundation bearing capacity method: The paper "Construction behavior simulation of a hydraulic tunnel during stand pipe" published in the journal "Tunnelling and Underground Space Technology" In the paper “Study on the jacking force of vertical jacking” published in the journal “Special Structures”, Wang et al. assumed that the jacking force exceeding the ultimate strength of the soil layer meant that the jacking force exceeded the ultimate strength of the soil layer, and introduced the Meyerhof theory to predict the jacking force; (2) Soil shear failure method: In the paper “Discussion on the calculation method of vertical jacking” published in the journal “Special Structures”, Wang Shousheng et al. assumed the distribution of the soil shear failure surface based on experience, and believed that the jacking force value is composed of the jacking pipe’s own weight, water weight, soil weight within the failure line, soil shear force on the failure line, and pipe-soil friction resistance; (3) Spherical hole expansion stress method: In the paper “Study on the jacking force of the whole process of vertical jacking construction” published in the journal “Journal of Rock Mechanics and Engineering”, Wei Xinjiang et al. believed that the head-on resistance of vertical jacking comes from the resistance of the vertical pipe caused by the yielding of the soil in the plastic zone. The shortcomings of the above methods are as follows: (1) There is a significant difference between the soil failure mode caused by the vertical jacking method and the foundation bearing capacity failure mode; (2) The soil shear failure method presupposes that the soil shear failure surface is a plane, but the soil shear failure surface during the vertical jacking construction process is a curved surface and changes dynamically with the jacking process; (3) The spherical hole expansion stress method is only applicable to the initial soil extrusion stage of jacking under deep burial conditions, and does not consider the influence of construction conditions such as grouting drag reduction and jacking speed on the pipe-soil friction resistance.

[0004] Therefore, it is necessary to revise and improve the existing methods and compare the calculated results with the measured values, so as to obtain a jacking force prediction method that can accurately reflect the dynamic changes of soil resistance during the entire vertical jacking construction process and is suitable for the overlying soil layer with a small thickness and under different construction conditions. Summary of the invention

[0005] In view of the shortcomings of the existing technology, the present invention proposes a method for predicting the vertical jacking force of submarine pipe jacking construction based on the modified shear theory. The method is suitable for the case where the thickness of the overlying soil layer is small and different construction conditions, and can accurately reflect the dynamic changes of soil resistance and jacking force in the whole process of vertical jacking construction.

[0006] The present invention provides the following technical solution: a method for predicting vertical lifting force of submarine pipe jacking construction based on modified shear theory, which specifically includes the following steps:

[0007] S100. Analyze the components of the lifting force F in vertical jacking construction: The lifting force F is numerically equal to the weight of the jacking pipe G. p , pipe wall friction resistance F f and the head-on resistance F h The sum of the head-on resistance F h The water pressure G above the top pipe w , weight of soil in shear failure plane G s and the soil cohesion resistance F on the shear failure surface c constitute;

[0008] S200, determining a rupture angle α': the rupture angle α' is the angle between the shear failure surface and the vertical line, and the rupture angle α satisfies the following expression:

[0009]

[0010] in is the equivalent internal friction angle and satisfies is the internal friction angle of the soil, c is the cohesion of the soil, γ s is the weight of the soil, γ w is the density of water; h h is the clear distance between the seabed and the front end of the jacking pipe and satisfies h h =h s -L, where h s is the clear distance between the seabed and the top of the horizontal tunnel, h w is the distance between the seabed and the sea surface, and L is the current pipe-jacking advancement distance. From the expression of the rupture angle α', it can be seen that the shear failure surface is not a plane, but a curved surface that changes with the pipe-jacking advancement distance.

[0011] S300, modifying the expression of the rupture angle α' according to the measured data: in the early stage of the vertical jacking method construction, the soil above the jacking pipe is in the extrusion stage, and the rupture angle α' value starts to increase from 0; in the middle and late stages of the vertical jacking method construction, with the expansion of the plastic zone and the penetration of the shear surface, the soil above the jacking pipe enters the shear failure state, and the α' value follows the expression of the rupture angle α' described in step S200; using the soil shear failure method to back-calculate the ratio of the jacking pipe advancement distance to the total jacking pipe advancement distance when the rupture angle α' reaches the maximum value, L / L0, assuming that the rupture angle α value in the early stage of the vertical jacking method construction is proportional to the 0.5 power of L / L0 and fitting is performed to obtain the modified rupture angle α expression:

[0012]

[0013] Where L0 is the total advancement distance of the jacking pipe, and when L / L0<0.235, the soil above the jacking pipe is in the extrusion stage, and when 0.235≤L / L0≤1, the soil above the jacking pipe is in the shear failure state;

[0014] S400, calculate the geometric parameters of the soil in the shear failure surface: when the outer contour section of the top pipe is circular, the geometric parameters of the soil in the shear failure surface satisfy the following expressions:

[0015]

[0016] Where D0 is the outer diameter of the top pipe, D1 is the top diameter of the soil in the shear failure plane, and V s is the volume of soil within the shear failure plane, A s is the lateral surface area of ​​the soil within the shear failure plane;

[0017] S500, calculate the head-on resistance F h Value: Water pressure above the top pipe G w Meet G w =S p ·(h w +h s ), where S p is the cross-sectional area of ​​the jacking pipe; the weight of the soil in the shear failure surface G s Meet G s =V s γ′; soil cohesion resistance F on the shear failure surface c Satisfy F c =A s c; the head-on resistance F h Satisfy F h =G w +G s +F c ;

[0018] S600, calculate the pipe wall friction resistance Ff : When no grouting drag reduction measures are taken, the pipe wall friction resistance F f It comes from the friction between the pipe wall and the soil; in the case of taking grouting to reduce drag, the pipe wall friction resistance F f The friction force between the pipe wall and the mud is: f satisfy:

[0019]

[0020] Where μ is the friction coefficient between the pipe wall and the soil, K is the lateral earth pressure coefficient and satisfies A l is the side wall surface area of ​​the top pipe, n p is the plastic viscosity, v is the average jacking speed of the jacking pipe, i is the thickness of the mud jacket, and τ0 is the initial shear stress;

[0021] S700, calculate the lifting force F: the lifting force F satisfies F=G p +F h +F f , and the lifting force F changes continuously with the current jacking pipe advancement distance L; when the soil above the jacking pipe is in the extrusion stage, that is, L / L0<0.235, the lifting force F value increases monotonically; when the soil above the jacking pipe is in the shear failure state, that is, 0.235≤L / L0≤1, the lifting force F value decreases monotonically; among them, the lifting force F reaches its maximum value when L / L0=0.235.

[0022] Furthermore, in S100, the weight of the jacking pipe G p Meet G p =nG p0 , where n is the number of jacking pipes, G p0 It is the deadweight of a single jacking pipe.

[0023] Further, in S400, when the cross-sectional shape of the outer contour of the top pipe is a square, the geometric parameters of the soil in the shear failure surface satisfy the following expression:

[0024]

[0025] Among them, B0 is the side length of the outer contour of the top pipe, and B1 is the top side length of the soil in the shear failure surface.

[0026] The present invention is based on the following principle analysis: In actual engineering, the failure morphology of the overlying soil layer in the vertical jacking construction stage changes with the progress of jacking and the depth of the overlying soil: in the early stage of vertical jacking construction, the soil above the jacking pipe is in the extrusion stage; in the middle and late stages of vertical jacking construction, with the expansion of the plastic zone and the penetration of the shear surface, the soil above the jacking pipe enters the shear failure state. Secondly, in the shear failure state stage, the shear failure surface is not a plane, but a curved surface that changes with the advancement distance of the jacking pipe, and has typical nonlinear characteristics. Based on the measured data, the present invention obtains the critical point where the failure morphology of the overlying soil layer in the vertical jacking construction stage changes from the extrusion stage to the shear failure state stage, at which the jacking pipe advancement distance L=0.235L0; and according to the Terzaghi theory for surrounding rock pressure calculation, the expression of the rupture angle α in the shear failure state stage is derived, thereby determining the geometric parameters of the soil in the shear failure surface and calculating the head-on resistance F h On the other hand, the friction resistance F f In the calculation of the pipe wall friction resistance F, if no grouting drag reduction measures are taken, f It mainly comes from the friction resistance between the pipe wall and the soil. At this time, the soil is in a loose state due to the disturbance of the vertical jacking method. The friction resistance between the pipe wall and the soil can be calculated according to the lateral earth pressure theory. For the case of taking grouting drag reduction measures, it is assumed that the mud is in full contact with the pipe wall and considering that the mud used for jacking drag reduction usually belongs to the bentonite system mud, the interaction mode between the soil, mud and pipe wall can be simplified to a flat plate popular model, and the friction resistance between the pipe wall and the mud can be calculated according to the Bingham plasticity model.

[0027] Compared with the prior art, the invention has the following beneficial effects: based on the existing soil shear failure method, the invention refers to the Terzaghi theory for calculating surrounding rock pressure and combines the measured data back analysis method to derive an expression for the change of the rupture angle α with the advancement distance of the jacking pipe, thereby accurately reflecting the dynamic changes of the soil morphology and the head-on resistance in the shear failure plane during the entire construction process of the vertical jacking method; the pipe wall friction resistance F f The calculation expression takes into account whether mud drag reduction is adopted during the vertical jacking method construction process, mud characteristics and the average jacking speed of the jacking pipe, and is suitable for a small thickness of the overlying soil layer and different construction conditions. The theory on which the present invention is based is more reasonable and the calculation process is relatively simple. It can be used to predict the jacking force of the entire actual vertical jacking method construction process and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the vertical lifting force prediction method of submarine pipe jacking construction based on the modified shear theory of the present invention;

[0029] Figure 2 It is the distribution diagram of the pipe jacking load during the whole construction process of the vertical jacking method of the present invention;

[0030] Figure 3 A comparison chart of the measured results of the drainage riser lifting force by Wei Xinjiang et al. and the theoretical value of the prediction method of the present invention;

[0031] Figure 4 A comparison chart of the jacking force of a drainage riser constructed by the vertical jacking method and the predicted value of the present invention;

[0032] Figure numerals: 1-horizontal tunnel, 2-lifting device, 3-sea surface, 4-seabed surface. DETAILED DESCRIPTION

[0033] The following is a more detailed description of the embodiments of the present invention in conjunction with the accompanying drawings and the accompanying drawings so that a person skilled in the art can implement the embodiments after reading the description. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The present invention provides Figure 1-4 The vertical lifting force prediction method for submarine pipe jacking construction based on the modified shear theory shown in the figure specifically includes the following steps:

[0035] S100. Analyze the components of the lifting force F in vertical jacking construction: The lifting force F is numerically equal to the weight of the jacking pipe G. p , pipe wall friction resistance F f and the head-on resistance F h The sum of the head-on resistance F h The water pressure G above the top pipe w , weight of soil in shear failure plane G s and the soil cohesion resistance F on the shear failure surface c The tube wall friction resistance F f and the head-on resistance F h This is the key content of the present invention. The lifting force F can be expressed as:

[0036] F=G p +F f +G w +G s +F c (1)

[0037] S200, determining the rupture angle α': the rupture angle α' is the angle between the shear failure surface and the vertical line. Referring to the Terzaghi theory for calculating the surrounding rock pressure, when the overburden failure mode in the vertical jacking construction stage is a shear failure state, the rupture angle α' increases with the net distance h between the seabed surface 4 and the front end of the jacking pipe. h The changed expressions are as follows:

[0038]

[0039] in is the equivalent internal friction angle and satisfies is the internal friction angle of the soil, c is the cohesion of the soil, γ s is the weight of the soil, γ w is the density of water; h h is the clear distance between the seabed surface 4 and the front end of the top pipe and satisfies h h =h s -L, where h s is the clear distance between the seabed surface 4 and the top surface of the horizontal tunnel 1, h w is the distance between the seabed surface 4 and the sea surface 3, and L is the current pipe-jacking advancement distance; from the expression of the rupture angle α', it can be seen that the shear failure surface is not a plane, but a curved surface that changes with the pipe-jacking advancement distance;

[0040] S300. Modify the expression of the rupture angle α' according to the measured data: in the initial stage of the vertical jacking method construction, the soil above the jacking pipe is in the extrusion stage, and the rupture angle α' value starts to increase from 0; in the middle and late stages of the vertical jacking method construction, with the expansion of the plastic zone and the penetration of the shear surface, the soil above the jacking pipe enters the shear failure state, and the α value follows the expression of the rupture angle α' described in step S200; the soil shear failure method is used to back-calculate the ratio of the jacking pipe advancement distance to the total jacking pipe advancement distance when the rupture angle α' reaches the maximum value, L / L0, assuming that the rupture angle α value in the initial stage of the vertical jacking method construction is proportional to the 0.5 power of L / L0.

[0041] The three representative drainage risers in a drainage engineering structure constructed by vertical jacking method are used as the engineering background. The drainage risers are all steel jacking pipes with a diameter of 0.5m and a wall thickness of 20mm. The distance h between the sea surface 3 and the seabed surface 4 is w is 14.4m, and the clear distance h between the seabed surface 4 and the top surface of the horizontal tunnel 1 is s The vertical jacking method is used to construct a coarse sand layer with a soil density of 19.8 kN / m 3 , the cohesion is 0, and the internal friction angle is 41.9°. The measured results of the lifting force of the vertical lifting method are compared with the theoretical values. Figure 3 shown.

[0042] Depend on Figure 3It can be seen that the measured results of the jacking force show a two-stage trend of increasing first and then decreasing, reflecting that the damage form of the overburden layer during the vertical jacking method construction stage changes from the extrusion stage to the shear damage state. Based on the measured data, the critical point where the damage form of the overburden layer during the vertical jacking method construction stage changes from the extrusion stage to the shear damage state, or the location where the maximum jacking force appears, occurs at the jacking pipe advancement distance L of 2.9m, 2.3m and 2.9m for drainage risers 1, 2 and 3, respectively. At this time, the ratio of the jacking pipe advancement distance to the total jacking pipe advancement distance L / L0 is 0.252, 0.2 and 0.252, respectively, with an average value of 0.235. According to the measured results, the critical point at which the failure mode of the overlying soil layer in the vertical jacking construction stage in the method of the present invention changes from the extrusion stage to the shear failure state stage is determined to be L / L0=0.235, that is, when the soil above the jacking pipe is in the extrusion stage, that is, L / L0<0.235, the jacking force F value increases monotonically; when the soil above the jacking pipe is in the shear failure state, that is, 0.235≤L / L0≤1, the jacking force F value decreases monotonically; wherein, the jacking force F reaches its maximum value at L / L0=0.235.

[0043] In the initial stage of vertical jacking construction, when L / L0<0.235, it is assumed that the rupture angle α value in the initial stage of vertical jacking construction is proportional to the 0.5 power of L / L0. The jacking force calculated is compared with the measured results. Figure 2 As shown in the figure, the development trend of the lifting force F is basically consistent with the advancement distance L of the jacking pipe.

[0044] In summary, based on the existing soil shear failure method, referring to the Terzaghi theory for surrounding rock pressure calculation and combining the measured data back analysis method, the modified rupture angle α expression is derived as follows:

[0045]

[0046] In addition, by Figure 3 It can be seen that the maximum lifting forces of drainage risers No. 1, 2 and 3 are 1920 kN, 2050 kN and 1750 kN respectively, with an average value of 1906.7 kN, which differs by about 2.6% from the maximum lifting force value of 1957.1 kN predicted by the present invention. Therefore, it can be considered that the prediction accuracy of the maximum lifting force by the method of the present invention is relatively high.

[0047] S400, calculate the geometric parameters of the soil in the shear failure plane: the geometric shape of the soil in the shear failure plane depends on the cross-sectional shape of the top pipe and the rupture angle α; since the rupture angle α varies with the advancement distance L of the top pipe and the clear distance h between the seabed surface 4 and the front end of the top pipe hTherefore, the geometric shape of the soil in the shear failure plane is not a truncated cone or a prism, and its geometric parameters need to be calculated using the integral method. For a jacking pipe with a circular outer contour and a diameter of D0, the top diameter D1 and volume V s and lateral surface area A s Satisfy the following expressions respectively;

[0048]

[0049] For a jacking pipe with a square outer contour and a side length of B0, the top side length B1 and volume V of the soil in the shear failure surface s and lateral surface area A s Satisfy the following expressions respectively:

[0050]

[0051] The determination of the geometric parameters of the soil within the shear failure plane is helpful in calculating the head-on resistance F h value.

[0052] S500, calculate the head-on resistance F h Value: Water pressure above the jacking pipe G w Meet G w =S p ·(h w +h s ), where S p is the cross-sectional area of ​​the top pipe, h w is the distance between the sea surface 3 and the seabed surface 4; the weight of the soil in the shear failure surface G s Meet G s =V s γ′; soil cohesion resistance F on the shear failure surface c Satisfy F c =A s c; the head-on resistance F h Satisfy F h =G w +G s +F c .

[0053] S600, calculate the pipe wall friction resistance F f : When no grouting drag reduction measures are taken, the pipe wall friction resistance F fIt mainly comes from the friction resistance between the pipe wall and the soil. At this time, the soil is in a loose state due to the disturbance of the vertical jacking method. The friction resistance between the pipe wall and the soil can be calculated according to the lateral earth pressure theory. For the case of taking grouting drag reduction measures, it is assumed that the mud is in full contact with the pipe wall and considering that the mud used for jacking drag reduction is usually bentonite system mud, the interaction mode between the soil, mud and pipe wall can be simplified to a flat plate model. The friction resistance between the pipe wall and the mud can be calculated according to the Bingham plasticity model. The pipe wall friction resistance F f Satisfies the following expression:

[0054]

[0055] Where μ is the friction coefficient between the pipe wall and the soil, K is the lateral earth pressure coefficient and satisfies A l is the side wall surface area of ​​the top pipe, n p is the plastic viscosity, v is the average jacking speed of the jacking pipe, i is the thickness of the mud jacket, and τ0 is the initial shear stress.

[0056] S700, calculate the lifting force F: the lifting force F satisfies F=G p +F h +F f , where the weight of the jacking pipe is G p Meet G p =nG p0 , where n is the number of jacking pipes, G p0 is the deadweight of a single jacking pipe. The lifting force F changes continuously with the current jacking pipe advancement distance L; when the soil above the jacking pipe is in the extrusion stage, that is, L / L0<0.235, the lifting force F value increases monotonically; when the soil above the jacking pipe is in the shear failure state, that is, 0.235≤L / L0≤1, the lifting force F value decreases monotonically; among them, the lifting force F reaches its maximum value when L / L0=0.235.

[0057] The technical effects of the technical solution of the present invention are further explained below in conjunction with specific embodiments.

[0058] Embodiment 1:

[0059] As an embodiment of the present invention, in the specific implementation: the integrated design and construction project of the drainage tunnels of Units 3 and 4 of the Zhangzhou Nuclear Power Plant adopts the drainage scheme of "shield starting pit + drilled and blasted tunnel + shield tunnel + drainage head". The drainage head structure at the end of the tunnel is equipped with 10 reinforced concrete drainage risers, all of which are constructed by vertical jacking method. The cross-sectional shape of the top pipe segment of the drainage riser is square, with an outer surface side length of 2.33m, an inner surface side length of 1.89m, and a segment wall thickness of 0.22m. The distance h between the sea surface and the seabed surface 4 is wis 12.47m, and the clear distance h between the seabed surface 4 and the top surface of the horizontal tunnel 1 is s The vertical jacking method is used to construct a silty clay layer with a soil density of 19.6 kN / m 3 , the cohesion is 7 kPa, and the internal friction angle is 28°. Substituting the above parameters into formula (3), the corrected rupture angle α is calculated as follows:

[0060]

[0061] The rupture angle α changes with the distance L (m) of the jacking pipe and the clear distance h between the seabed surface 4 and the front end of the jacking pipe. h (m) varies, where h h =8.64-L.

[0062] Substituting the above parameters and calculation results into formula (5), we can obtain the volume V of the soil within the shear failure surface: s and lateral surface area A s The water pressure G above the jacking pipe is calculated based on the calculation result of the jacking pipe advancement distance L. w , the weight of the soil in the shear failure plane G s , the soil cohesion resistance F on the shear failure surface c , and thus the head-on resistance F is calculated h The corresponding calculation results are shown in Table 1.

[0063] In the case where no grouting drag reduction measures are taken, the pipe wall friction resistance F f It can be calculated according to formula (6). p It can be determined according to the jacking distance L. Substituting the above parameters and calculation results into formula (1), the jacking force F of the whole process of vertical jacking construction is calculated. The calculation results are shown in Table 1.

[0064] Table 1 Summary of calculation results of Example 1

[0065]

[0066] It can be seen from Table 1 that, without taking grouting drag reduction measures, the jacking force F predicted by the method of the present invention shows a trend of first increasing sharply and then decreasing slowly with the change of the jacking pipe advancement distance L, which is in line with the actual situation; the maximum jacking force predicted by the method of the present invention is 6736.6 kN, which can provide a reference for the jacking pipe segment structure design, tunnel bottom reinforcement design, jacking device 2 configuration, and whether to take mud drag reduction measures in actual projects.

[0067] Embodiment 2:

[0068] As an embodiment of the present invention, in the specific implementation: during the vertical jacking method construction process, mud drag reduction measures are taken, by pouring bentonite system mud between the side wall of the top pipe and the soil, so that the mud is fully in contact with the pipe wall, thereby reducing the friction resistance F of the pipe wall f The plastic viscosity of the mud used is n p is 25kPa·s, the initial shear stress τ0 is 15kPa; the average jacking speed v of the jacking pipe is 0.1m / s, and the mud jacket thickness i is 0.4m.

[0069] That is, the other situations and conditions of Example 2 are the same as those of Example 1, and the only difference is that mud drag reduction measures are taken during the vertical jacking method construction process.

[0070] Substituting the above parameters and related calculation results into formula (6), the friction resistance F of the pipe wall with grouting drag reduction measures is calculated. f The calculation results are shown in Table 2.

[0071] Table 2 Summary of calculation results of Example 2

[0072]

[0073] As shown in Table 2, after taking the grouting drag reduction measure, the average lifting force is reduced by about 12%, and the maximum lifting force is reduced by about 6%. It can be considered that the grouting drag reduction measure can reduce the lifting force required for vertical jacking construction, but due to the friction resistance F f It accounts for a small proportion in the lifting force F, so the effect of grouting drag reduction measures is not significant enough.

[0074] The above are one or more embodiments of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for predicting vertical lifting force in submarine pipe jacking construction based on modified shear theory, characterized in that The following steps are involved: S100. Analyze the components of the lifting force F in vertical jacking construction: The lifting force F is numerically equal to the weight of the jacking pipe G. p , pipe wall friction resistance F f and the head-on resistance F h The sum of the head-on resistance F h The water pressure G above the top pipe w , weight of soil in shear failure plane G s and the soil cohesion resistance F on the shear failure surface c constitute; S200, determining a rupture angle α': the rupture angle α' is the angle between the shear failure surface and the vertical line, and the rupture angle α' satisfies the following expression: in is the equivalent internal friction angle and satisfies is the internal friction angle of the soil, c is the cohesion of the soil, γ s is the weight of the soil, γ w is the density of water; h h is the clear distance between the seabed and the front end of the jacking pipe and satisfies h h =h s -L, where h s is the clear distance between the seabed and the top of the horizontal tunnel, h w is the distance between the seabed and the horizontal tunnel, and L is the current pipe jacking advancement distance; S300, modify the expression of the rupture angle α' according to the measured data: the modified expression of the rupture angle α is as follows: Where L0 is the total advancement distance of the jacking pipe; S400, calculate the geometric parameters of the soil in the shear failure surface: when the outer contour section of the top pipe is circular, the geometric parameters of the soil in the shear failure surface satisfy the following expressions: Where D0 is the outer diameter of the top pipe, D1 is the top diameter of the soil in the shear failure plane, and V s is the volume of soil within the shear failure plane, A s is the lateral surface area of ​​the soil within the shear failure plane; S500, calculate the head-on resistance F h Value: Water pressure above the jacking pipe G w Meet G w =S p ·(h w +h s ), where S p is the cross-sectional area of ​​the jacking pipe; the weight of the soil in the shear failure surface G s Meet G s =V s γ′; soil cohesion resistance F on the shear failure surface c Satisfy F c =A s c; the head-on resistance F h Satisfy F h =G w +G s +F c ; S600, calculate the pipe wall friction resistance F f Value: The pipe wall friction resistance F f satisfy: Where μ is the friction coefficient between the pipe wall and the soil, K is the lateral earth pressure coefficient and satisfies A l is the side wall surface area of ​​the top pipe, n p is the plastic viscosity, v is the average jacking speed of the jacking pipe, i is the thickness of the mud jacket, and τ0 is the initial shear stress; S700, calculate the lifting force F value: the lifting force F satisfies F=G p +F h +F f .

2. The method for predicting vertical lifting force of submarine pipe jacking construction based on modified shear theory according to claim 1 is characterized in that: In step S100, the weight of the jacking pipe G p Meet G p =nG p0 , where n is the number of jacking pipes, G p0 It is the deadweight of a single jacking pipe.

3. The method for predicting vertical lifting force of submarine pipe jacking construction based on modified shear theory according to claim 1 is characterized in that: In step S400, when the cross-sectional shape of the outer contour of the top pipe is a square, the geometric parameters of the soil in the shear failure plane satisfy the following expression: Among them, B0 is the side length of the outer contour of the top pipe, and B1 is the top side length of the soil in the shear failure surface.

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