A large-scale caisson soil extraction control method based on soil critical state

Abstract

The present application relates to the field of foundation engineering, and discloses a large-scale caisson soil extraction control method based on the critical state of soil, comprising the following steps: obtaining the soil layer distribution and physical and mechanical parameters of the caisson location, establishing an interaction model between the caisson blade and the soil, calculating the pressure distribution in the blade contact area by the finite element method, simulating the distribution of the plastic zone of the soil and performing a connectivity analysis; designing a caisson soil extraction construction plan based on the above analysis, the plan including the soil extraction sequence, soil extraction depth and plastic zone ratio index; judging by simulation whether the construction plan meets the safety and stability requirements of the caisson sinking, and if not, adjusting the soil extraction parameters and re-verifying until the requirements are met. The present invention realizes the precise design and dynamic adjustment of the caisson sinking process through the dual control of the plastic zone ratio index and the connectivity index, and significantly improves the safety, stability and reliability of the construction.

Description

Technical Field

[0001] The invention relates to the technical field of foundation engineering, and in particular to a large-scale caisson soil extraction control method based on a critical state of soil. Background Art

[0002] Caisson is a structural form widely used in deep foundation engineering. Its sinking construction process directly affects the safety and stability of the entire project. Caisson sinks gradually by taking soil. Traditional construction methods mainly rely on field experience to determine the order, depth and distribution of soil taking. However, the heterogeneity of soil, complex geological conditions and nonlinear interaction between blade foot and soil often lead to significant uncertainty in the sinking process of caisson. For example, uneven soil taking may cause excessive force on the blade foot, resulting in tilting or local settlement of the caisson; at the same time, taking soil too deep or too quickly may cause the soil to enter an unstable state, thus causing serious engineering accidents such as sudden sinking.

[0003] Existing technologies have obvious deficiencies in addressing the safety and stability of caisson construction. Specifically, traditional construction designs often lack systematic research on soil failure mechanisms and lack quantitative analysis methods for the interaction between the caisson blade and the soil. In addition, existing construction plans usually fail to effectively combine the critical state characteristics of the soil, making it difficult to accurately control the distribution and connectivity of the plastic zone of the soil, resulting in construction plans that are difficult to adapt to complex geological conditions and engineering requirements. In addition, due to the lack of scientific prediction and evaluation of the caisson sinking process, on-site construction adjustments are often quite arbitrary, increasing safety risks and engineering costs during the construction process.

[0004] Therefore, a new caisson soil extraction control method based on soil critical state analysis is needed, which can reasonably control the soil extraction sequence, depth and distribution through scientific modeling and parametric design, achieve safety and stability control of the caisson sinking process, and overcome the defects and shortcomings of the existing technology. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a large-scale caisson soil extraction control method based on the critical state of the soil, which solves the problem that the caisson construction scheme in the prior art is difficult to accurately control the distribution and connectivity of the plastic zone of the soil, resulting in insufficient safety and stability in the caisson sinking process.

[0006] To achieve the above purpose, the present invention is implemented by the following technical scheme: a large-scale caisson soil extraction control method based on the critical state of soil, comprising the following steps:

[0007] Obtain soil layer distribution and physical and mechanical parameters at the location of the caisson;

[0008] Based on the soil layer distribution and physical and mechanical parameters, an interaction model between the caisson blade foot and the soil is established. The model calculates the pressure distribution in the blade foot contact area by the finite element method, simulates the distribution of the plastic zone of the soil, and performs connectivity analysis of the plastic zone.

[0009] Design a construction plan for soil excavation in the caisson, including soil excavation sequence, soil excavation depth and plastic zone ratio index;

[0010] Determining whether the construction scheme meets the safety and stability requirements of the caisson sinking state, the determination being based on a plastic zone proportion index and a plastic zone connectivity index;

[0011] If the construction plan meets the requirements, the soil excavation construction is carried out, otherwise the construction plan is adjusted and the verification steps are repeated.

[0012] Preferably, the soil layer distribution includes at least the soil type and the boundary elevation of adjacent soil layers, and the physical and mechanical parameters include the dry weight, saturated weight, water content, deformation modulus, Poisson's ratio, cohesion, internal friction angle and dilatancy angle of the soil.

[0013] Preferably, the critical state of the soil is determined by observing the continuity of the plastic zone in the model calculation results. When the plastic zone is completely connected, the soil reaches a critical state.

[0014] Preferably, the establishment of the interaction model between the blade foot and the soil comprises the following steps:

[0015] Obtain the soil layer distribution and physical and mechanical parameters of the contact area between the caisson blade and the soil, and define the finite element division of the contact area between the blade and the soil;

[0016] Based on the blade foot contact area, the contact pressure distribution function is established , which is decomposed into vertical pressure and horizontal shear stress ;

[0017] The finite element method is used to perform mechanical calculations on the blade foot contact area and calculate the total resistance of the contact area , the total resistance formula is:

[0018] ;

[0019] in, is the shear stress, is the normal stress, is the contact area unit area;

[0020] The calculation results are used to simulate the distribution of the plastic zone in the contact area between the caisson blade and the soil, and to determine the penetration range of the plastic zone.

[0021] Preferably, the finite element division of the blade foot contact area includes dividing the contact surface between the bottom of the blade foot and the soil into a plurality of regular grid units, and calculating the vertical pressure and shear stress distribution for each unit respectively.

[0022] Preferably, in the caisson soil excavation construction plan:

[0023] The order of soil sampling is to first sample the soil from the inner well hole and then the soil from the outer well hole. The sampling range gradually expands from the center of the well hole to the surrounding area and is symmetrical on the plane.

[0024] The soil sampling depth of the outer well hole is lower than that of the inner well hole, and the depth difference satisfies ;

[0025] Plastic zone ratio index The range is .

[0026] Preferably, the step of judging whether the construction scheme meets the safety and stability requirements of the caisson sinking state includes:

[0027] The distribution of the plastic zone in the blade foot contact area is calculated by numerical model, and the area of ​​the plastic zone is obtained. Total contact area with blade foot , calculate the plastic zone ratio index , to determine whether it meets the set range, the formula is: ;

[0028] Determine the number of continuous failure paths in the plastic zone through connectivity analysis of the plastic zone in the numerical model , when the preset requirements are met, it means that sufficient penetration failure paths are formed;

[0029] like and If all requirements are met, the construction plan is judged to be able to ensure the safe and stable sinking of the caisson; otherwise, the construction plan is adjusted and re-verified.

[0030] Preferably, the adjustment of the construction scheme comprises the following steps:

[0031] When the model calculation results show that the plastic zone ratio index does not meet the reasonable distribution range, the ratio of soil extraction from the inner well hole and the outer well hole is adjusted, the soil extraction from the inner well hole is increased or decreased, and the soil extraction depth difference of the outer well hole is adjusted simultaneously;

[0032] When the connectivity index of the plastic zone does not meet the requirements, the soil sampling sequence is adjusted to give priority to the inner borehole area and gradually expand to the outer borehole area;

[0033] If uneven force is applied to the blade foot area, resulting in a tilting trend, the force on one side of the soil can be reduced by adjusting the amount of soil taken in the tilting direction, and the soil taking range on the opposite side can be increased to balance the force.

[0034] After each adjustment, the distribution and connectivity of the plastic zone are re-verified, and adjustments are made cyclically until the construction plan meets the safety and stability requirements of the caisson sinking state.

[0035] The present invention provides a large-scale caisson soil extraction control method based on the critical state of soil, which has the following beneficial effects:

[0036] 1. The present invention uses the dual constraints of the plastic zone ratio index and the connectivity index to scientifically judge the critical state of the soil, avoiding the problem of sudden or stagnant settlement caused by insufficient or excessive soil damage. The construction plan always maintains uniform force during the sinking process, thereby reducing the risk of tilting and local instability. The construction is guided by numerical simulation, avoiding the safety hazards brought by traditional empirical methods.

[0037] 2. The present invention can optimize the soil extraction depth and distribution in real time through finite element analysis and dynamic adjustment of the construction plan to ensure balanced pressure distribution in the blade foot contact area. The soil extraction sequence and depth difference of the inner and outer wellbores are precisely controlled to ensure a smooth and controllable sinking process. The through-path design of the plastic zone provides clear sinking direction guidance, effectively avoiding irregular sinking problems.

[0038] 3. The present invention adopts a dynamic adjustment mechanism to optimize the soil excavation parameters in a timely manner according to the simulation results, and ensures that the scheme meets the safety requirements through cyclic verification. The scientific adjustment of the soil excavation depth, range and sequence improves the efficiency of the scheme design and enhances the flexibility of the construction process. The method can be flexibly adapted under complex geological conditions to ensure that the construction plan can meet actual needs.

[0039] 4. The present invention provides technical processes and reference indicators for construction through numerical simulation, step-by-step design and parametric control methods. The quantitative evaluation of the plastic zone proportion PCR and the through path CPI facilitates on-site operators to quickly judge the feasibility of the construction plan. The combination of computer simulation and parametric adjustment greatly reduces the blindness and trial and error costs of construction design. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the specification of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Please see attached Figure 1 The present invention provides a large-scale caisson soil extraction control method based on the critical state of soil. By acquiring the physical and mechanical parameters of the soil, an interaction model between the blade foot and the soil is constructed, a reasonable construction plan is designed, and the plan is simulated, verified and optimized, ultimately achieving safe and smooth control of the caisson sinking process.

[0043] The large-scale caisson soil extraction control method based on the critical state of soil may include the following steps:

[0044] S1. Obtain soil layer distribution and physical and mechanical parameters at the location of the caisson;

[0045] S2. Based on soil layer distribution and physical and mechanical parameters, establish the interaction model between caisson blade and soil;

[0046] S3. Design the construction plan for caisson soil excavation;

[0047] S4, judging whether the construction scheme meets the safety and stability requirements of the caisson sinking state;

[0048] S5. If the construction plan meets the requirements, carry out the soil excavation construction, otherwise adjust the construction plan and repeat the verification steps.

[0049] Each step of the method of the present invention is described in detail below.

[0050] For step S1, a variety of conventional geological survey techniques and laboratory testing methods are used to obtain the soil layer distribution and physical and mechanical parameters at the location of the caisson, so as to fully ensure the accuracy and applicability of subsequent model establishment and scheme design.

[0051] In the process of obtaining the soil layer distribution, the interlayer structure and distribution characteristics of the soil are determined through the drilling exploration technology in the caisson area. Specifically, the main soil layer types in the caisson area are determined according to the geological survey report, including sand, clay, silt, fill, etc., and the boundary elevation and layer thickness information of adjacent soil layers are recorded based on the drilling depth.

[0052] To ensure data integrity, soil layer distribution data must include the following:

[0053] Soil type in the caisson blade area;

[0054] Soil layer thickness and inter-layer position elevation;

[0055] Analysis of continuity and uniformity of characteristic soil layers;

[0056] The possible existence of discontinuous interfaces (such as hard interlayers, soft interlayers, etc.).

[0057] In the process of obtaining physical and mechanical parameters, detailed indoor geotechnical tests are carried out in combination with drilling sampling. The main physical and mechanical parameters obtained include:

[0058] The dry weight and saturated weight of soil are used to describe the basic weight characteristics of soil and are determined by the oven drying method;

[0059] Moisture content, used to reflect the moisture content of soil, is obtained using standard test methods;

[0060] Elastic modulus of soil and Poisson's ratio , determined by indoor triaxial tests, where the elastic modulus is used to describe the stress-strain relationship of the soil in the elastic stage, and the Poisson's ratio is used to describe the ratio of lateral deformation to longitudinal deformation;

[0061] Cohesion and internal friction angle , as the key indicator of soil shear strength, the Mohr-Coulomb strength theory is used:

[0062] ;

[0063] in, is the shear stress, is the normal stress, It represents the friction characteristics between soil particles;

[0064] Shear dilation angle , which is used to describe the volume expansion characteristics of soil under shear and can be determined by triaxial shear test.

[0065] In order to meet the implementation requirements of the present invention, it is also necessary to analyze the additional parameters such as compressive strength, permeability, density, etc. of different soil layers. Taking the sand layer as an example, its permeability is determined by the permeability coefficient Characterize the compressive strength of the clay layer by the undrained shear strength Description, these parameters directly affect the formation conditions of the plastic zone of the soil.

[0066] In the process of acquiring the above data, it is necessary to combine the specific regional characteristics and project scale of the caisson construction to ensure the accuracy and applicability of the parameter acquisition. The sampling point layout should cover the sinking path of the caisson and the surrounding key soil layer areas to ensure the comprehensiveness and uniformity of the data.

[0067] By acquiring soil layer distribution and physical and mechanical parameters, this embodiment ensures that the interaction between the caisson blade and the soil can be reflected when the subsequent model is established, providing data support for the design of the caisson soil excavation construction plan.

[0068] For step S2, in this embodiment, a model of the interaction between the caisson blade and the soil is established, and the contact area of ​​the caisson blade is accurately modeled and mechanically analyzed in combination with the finite element analysis method, and the pressure distribution in the contact area and the plastic zone distribution of the soil are simulated to achieve the design and evaluation of the caisson soil extraction process.

[0069] First, the soil layer distribution and physical and mechanical parameters of the caisson blade contact area are obtained, including soil layer type, thickness, cohesion, , internal friction angle , elastic modulus , Poisson's ratio The key parameters are provided by step S1. These parameters are used to define the material properties and mechanical behavior of the contact area between the caisson blade and the soil, providing a basic guarantee for the accuracy of the model.

[0070] Next, based on the geometric size of the caisson blade foot and the soil distribution in the contact area, the finite element meshing technology is used to divide the contact area between the bottom of the blade foot and the soil into multiple regular finite elements. The shape of the divided element is usually a two-dimensional quadrilateral or a three-dimensional hexahedron. The number of elements needs to be set in combination with the size of the caisson blade foot and the complexity of the contact pressure distribution to ensure the accuracy and efficiency of the calculation results.

[0071] For the blade foot contact area, define its contact pressure distribution function ,in It represents the pressure distribution at a certain point at the bottom of the blade foot. The pressure distribution function is decomposed according to the deadweight of the blade foot and the reaction force of the soil, and is decomposed into vertical pressure and horizontal shear stress .in:

[0072] ;

[0073] ;

[0074] in, is the load in the vertical direction, is the unit area, is the friction coefficient of soil, which is used to describe the distribution characteristics of horizontal shear stress.

[0075] The finite element method is used to perform overall mechanical calculations on the blade foot contact area. The core of mechanical calculations is to solve the total resistance of the contact area. According to the soil shear strength theory, the total resistance formula of the contact area is:

[0076] ;

[0077] in, is the shear stress distribution, is the normal stress distribution, is the unit area of ​​the contact area. Through finite element meshing, the contact area is discretized into The stress of each unit is numerically integrated to obtain the total resistance.

[0078] After the total resistance calculation is completed, the Mohr-Coulomb criterion in soil mechanics is used to determine whether the soil in the contact area has entered a plastic state. The plastic state is determined by the following formula:

[0079] ;

[0080] When the shear stress meets the above conditions, the element is judged to be in a plastic state. By judging all elements one by one, the distribution of the plastic zone in the contact area can be obtained.

[0081] In order to further analyze the stability and sinking safety of the soil, the connectivity of the plastic zone is also evaluated in this embodiment. The connectivity of the plastic zone is a key indicator to measure whether the soil has entered a critical state. By analyzing whether a continuous through path is formed in the plastic zone, the destruction trend of the soil in the contact area can be determined. Specifically, if the plastic zone continuously penetrates from the edge of the blade to the deep soil, it indicates that the soil has reached a critical failure state. The number and direction of the connection paths can be intuitively identified through the numerical simulation results and cloud maps of the plastic zone distribution.

[0082] In summary, this embodiment completely realizes the establishment and analysis of the interaction model between the caisson blade and the soil through finite element meshing, contact pressure distribution function calculation, total resistance solution and plastic zone connectivity analysis. The model calculation results can provide a scientific basis for the design of subsequent caisson construction plans and effectively predict the safety and stability of the caisson during the sinking process.

[0083] For step S3, in this embodiment, the design of the caisson soil excavation construction plan is based on the aforementioned model analysis and calculation results, combined with the interaction characteristics between the caisson blade and the soil, to reasonably determine the soil excavation sequence, soil excavation depth, soil excavation range and the control range of the plastic zone proportion index PCR, thereby ensuring the safety and stability of the caisson sinking process.

[0084] First, the soil taking sequence in this embodiment is designed according to the principle of "from inside to outside, gradually expanding". Specifically, soil taking construction starts with the soil of the inner well hole first, and then gradually expands to the outer well hole. The soil taking range of the inner and outer well holes maintains symmetry on the plane to ensure the uniformity of force on the contact area at the bottom of the caisson blade foot as much as possible.

[0085] The expansion method of the soil sampling range is optimized based on the simulation results of the plastic zone distribution in the model calculation. Initially, the soil sampling starts from the center of the wellbore and gradually expands to the surrounding areas. At the same time, the distribution trend of the blade foot contact pressure is monitored to ensure that the expansion range can maintain a stable distribution within the plastic zone proportion index range. This expansion strategy aims to control the pressure concentration effect in different areas at the bottom of the blade foot and avoid local tilting or soil instability caused by uneven soil sampling.

[0086] Secondly, the soil sampling depth is designed to follow the distribution pattern of "high inside and low outside". In this embodiment, the soil sampling depth of the inner well hole is higher than the soil sampling depth of the outer well hole, and the depth difference between the two meets the following range:

[0087] ;

[0088] in, It represents the difference between the soil extraction depth of the inner well hole and the outer well hole. The range is determined according to the development characteristics of the plastic zone in the simulation analysis. Through the above design, it can effectively ensure that the plastic zone is formed first in the inner well hole area, thereby promoting the stable sinking of the caisson and preventing excessive soil extraction in the outer well hole area from causing the blade foot to tilt or local overload.

[0089] Furthermore, this embodiment uses the plastic zone ratio index PCR to quantitatively evaluate the construction plan to ensure that the soil is within a reasonable critical state range. The plastic zone ratio index PCR is defined as follows:

[0090] ;

[0091] in, is the plastic zone area of ​​the blade foot contact area, is the total area of ​​the blade foot contact area. In this embodiment, combined with the finite element simulation results, the reasonable range of PCR is determined as:

[0092] ;

[0093] Within this range, the distribution of the plastic zone of the soil is sufficient to support the steady sinking of the caisson without causing sudden or stagnant sinking. If PCR < 0.7, it means that the plastic zone is insufficient and the soil has not yet entered a critical state; if PCR > 0.9, it means that the plastic zone is excessive and the soil may enter an unstable sudden sinking state. Therefore, during the construction process, it is necessary to strictly control PCR within the above range.

[0094] When designing the construction plan, it is also necessary to combine the results of the plastic zone connectivity analysis in the model simulation to ensure that the distribution direction of the plastic zone penetration path is consistent with the direction of the caisson's deadweight. Through the combined simulation of different soil excavation depths and sequences, the soil excavation parameters are optimized so that the plastic zone penetration direction can form a stable continuous failure path in the blade foot area. The formation of this path helps to guide the sinking direction of the caisson and prevent the tilting and sinking caused by uneven force on the soil in the blade foot contact area.

[0095] In summary, the caisson soil excavation construction plan in this embodiment achieves precise control of the caisson sinking state by reasonably designing the soil excavation sequence, soil excavation depth and plastic zone ratio index control.

[0096] For step S4, in this embodiment, whether the construction plan meets the safety and stability requirements of the caisson sinking state is determined by combining the numerical model and simulation results established in the previous steps, and a comprehensive evaluation is made on the distribution and connectivity of the plastic zone in the blade foot contact area to judge the feasibility and safety of the construction plan.

[0097] In the process of judging the construction plan, the distribution of the plastic zone in the blade foot contact area is first simulated by the numerical model established above. The distribution of the plastic zone is the key to judging whether the soil has entered a critical state. By calculating the plastic zone area in the blade foot contact area and total contact area , and further calculate the plastic zone ratio index PCR. The plastic zone ratio PCR is used to measure the degree to which the soil in the contact area enters the plastic state, and its reasonable range is 0.7≤PCR≤0.9. When PCR is within this range, it means that the soil is in a safe and stable critical state. If PCR<0.7, it means that the plastic zone is insufficient, and the soil in the blade contact area has not yet fully entered the critical state, which may lead to a decrease in the sinking efficiency of the caisson; if PCR>0.9, it means that there are too many plastic zones, and the soil in the contact area may experience unstable sudden sinking.

[0098] In addition, in this embodiment, the connectivity analysis of the plastic zone is an important part of evaluating the construction plan. The connectivity of the plastic zone in the blade foot contact area is calculated through a numerical model to determine whether the plastic zone forms sufficient continuous failure paths. The connectivity of the plastic zone is represented by the number of through failure paths CPI. When the CPI reaches the preset requirements, it means that the plastic zone has formed a continuous through failure path in the blade foot contact area, which can effectively support the stable sinking of the caisson.

[0099] The calculation of the number of through failure paths in the plastic zone, CPI, is based on the numerical simulation results of the distribution of the plastic zone. By analyzing the connectivity of the grid cells in the plastic zone of the blade foot contact area one by one, it is determined whether there is a continuous failure path from the edge of the blade foot to the deep soil. If there are insufficient paths (for example, the CPI value is small), it means that the soil in the blade foot contact area has not reached a sufficient critical state, which may lead to unevenness or tilt risks during the sinking of the caisson.

[0100] In this embodiment, the calculation results must meet the requirements of both PCR and CPI to determine whether the construction plan can ensure the safety and stability of the caisson sinking state. If any indicator does not meet the requirements, such as PCR exceeds the reasonable range or CPI is insufficient, the construction plan needs to be adjusted, including modifying parameters such as soil excavation depth, soil excavation sequence or soil excavation range. The adjusted construction plan needs to be re-entered into the model for simulation verification until all evaluation indicators meet the requirements.

[0101] In summary, this embodiment can scientifically and accurately evaluate whether the construction plan meets the safety and stability requirements of caisson sinking through the comprehensive judgment of the plastic zone proportion index PCR and the number of through failure paths CPI.

[0102] For step S5, in this embodiment, a dynamic adjustment mechanism based on model calculation is proposed for the situation that the construction plan does not meet the safety and stability requirements of the caisson sinking state. The adjustment mechanism combines the calculation results of the plastic zone proportion index PCR and the connectivity index CPI, optimizes the construction plan by modifying the soil sampling parameters, and re-verifies the adjusted plan until the plan meets the design requirements.

[0103] First, when the model calculation results show that the plastic zone ratio index PCR does not meet the reasonable distribution range, it is necessary to adjust the ratio of soil extraction from the inner wellbore to the outer wellbore. Specifically, when the PCR value is lower than the reasonable range (for example, PCR < 0.7), it means that the soil in the blade foot contact area has not entered the plastic state. At this time, it is preferred to increase the soil extraction from the inner wellbore and reduce the soil extraction from the outer wellbore. After adjustment, the distribution of the plastic zone is verified.

[0104] If the PCR value is higher than the reasonable range (for example, PCR>0.9), it means that there are too many plastic zones and the soil may enter a sudden subsidence state. At this time, it is necessary to reduce the amount of soil taken from the inner well hole and appropriately increase the depth difference of soil taken from the outer well hole. Adjusted depth difference The preset range should be met again, and the adjustment principle should be aimed at controlling the soil in the contact area of ​​the blade foot to enter a reasonable critical state.

[0105] Secondly, when the plastic zone connectivity index CPI calculated by the model does not meet the preset requirements, it means that there are not enough continuous failure paths in the blade foot contact area, and the soil extraction sequence needs to be adjusted. During the adjustment, the inner wellbore area is given priority for concentrated soil extraction, and then gradually expanded to the outer wellbore area. The concentrated soil extraction in the inner wellbore area can preferentially form a through path of the plastic zone in the center of the blade foot contact area, and then expand outward to form a complete failure network. The adjusted soil extraction sequence should be continuously optimized in combination with the dynamic simulation results of the plastic zone distribution.

[0106] If the model calculation shows that the blade foot contact area is unevenly stressed, resulting in a tilting trend in the caisson, it is necessary to balance the stress state at the bottom of the blade foot by adjusting the amount of soil taken in the tilting direction. Specifically, reduce the amount of soil taken in the inner or outer wellbore area in the tilting direction, while increasing the amount or range of soil taken on the opposite side. This adjustment requires real-time simulation and calculation of the changes in the blade foot contact pressure distribution P(x,y) to ensure that the force at the bottom of the blade foot tends to be uniform after adjustment to eliminate the tilting trend.

[0107] In the above adjustment process, each adjusted construction plan needs to be re-entered into the model for verification, including the plastic zone ratio index PCR, connectivity index CPI, blade foot contact pressure distribution and overall stability of the soil. If the adjusted construction plan still does not meet the requirements, continue to iteratively adjust the soil extraction amount, soil extraction depth and soil extraction sequence until the model calculation results meet all design indicators.

[0108] Through the above adjustment mechanism, this embodiment ensures that the construction plan meets the requirements of safety and stability before construction. During the adjustment process, combined with the above finite element model analysis results, the influence of different adjustment parameters on the distribution of plastic zone and the force in the contact area can be accurately predicted, thereby providing an efficient and scientific adjustment basis.

[0109] To sum up, this embodiment can effectively deal with potential risks caused by complex soil conditions or insufficient initial plans by adjusting the soil excavation depth, soil excavation sequence and soil excavation range in the construction plan and combining it with a dynamic verification mechanism, thereby ensuring the safety and stability of the caisson sinking process and improving the accuracy and operability of the scheme design.

[0110] In general, the present invention obtains the soil layer distribution and physical and mechanical parameters of the caisson location, establishes an interaction model between the caisson blade and the soil, uses the finite element method to calculate the pressure distribution in the blade contact area and simulates the distribution and connectivity of the plastic zone of the soil, designs a reasonable soil excavation construction plan, including the soil excavation sequence, soil excavation depth and plastic zone ratio index, and then determines whether the construction plan meets the safety and stability requirements of the caisson sinking. If the plan does not meet the requirements, it is optimized and re-verified by adjusting the soil excavation parameters until the requirements are met. The present invention combines numerical simulation with parameter adjustment to achieve precise control of the sinking state during the caisson construction process, thereby improving the safety, stability and reliability of the construction.

[0111] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A large-scale caisson soil extraction control method based on soil critical state, characterized in that: The following steps are involved: Obtain soil layer distribution and physical and mechanical parameters at the location of the caisson; Based on the soil layer distribution and physical and mechanical parameters, an interaction model between the caisson blade foot and the soil is established. The model calculates the pressure distribution in the blade foot contact area by the finite element method, simulates the distribution of the plastic zone of the soil, and performs connectivity analysis of the plastic zone. Design a construction plan for soil excavation in the caisson, including soil excavation sequence, soil excavation depth and plastic zone ratio index; Determining whether the construction scheme meets the safety and stability requirements of the caisson sinking state, the determination being based on a plastic zone proportion index and a plastic zone connectivity index; If the construction plan meets the requirements, the soil excavation construction is carried out, otherwise the construction plan is adjusted and the verification steps are repeated; The establishment of the interaction model between the blade foot and the soil includes the following steps: Obtain the soil layer distribution and physical and mechanical parameters of the contact area between the caisson blade and the soil, and define the finite element division of the contact area between the blade and the soil; Based on the blade foot contact area, the contact pressure distribution function is established , which is decomposed into vertical pressure and horizontal shear stress ,in: ； ； in, is the load in the vertical direction, is the unit area, is the friction coefficient of soil; The finite element method is used to perform mechanical calculations on the blade foot contact area and calculate the total resistance of the contact area , the total resistance formula is: ； in, is the shear stress, is the normal stress, is the contact area unit area; After the total resistance calculation is completed, the following formula is used to determine whether the soil in the contact area has entered a plastic state: ； in, For cohesion, is the internal friction angle; The calculation results are used to simulate the distribution of the plastic zone in the contact area between the caisson blade and the soil, and to determine the penetration range of the plastic zone.

2. A large-scale caisson soil extraction control method based on soil critical state according to claim 1, characterized in that: The soil layer distribution includes at least the soil type and the boundary elevation of adjacent soil layers, and the physical and mechanical parameters include the dry weight, saturated weight, water content, deformation modulus, Poisson's ratio, cohesion, internal friction angle and shear dilation angle of the soil.

3. A large-scale caisson soil extraction control method based on soil critical state according to claim 1, characterized in that: The critical state of the soil is determined by observing the continuity of the plastic zone in the model calculation results. When the plastic zone is completely connected, the soil reaches a critical state.

4. A large-scale caisson soil extraction control method based on soil critical state according to claim 1, characterized in that: The finite element division of the blade foot contact area includes dividing the contact surface between the bottom of the blade foot and the soil into a plurality of regular grid units, and calculating the vertical pressure and shear stress distribution for each unit respectively.

5. The large-scale caisson soil extraction control method based on soil critical state according to claim 1 is characterized in that: In the caisson soil excavation construction plan: The order of soil sampling is to first sample the soil from the inner well hole and then the soil from the outer well hole. The sampling range gradually expands from the center of the well hole to the surrounding area and is symmetrical on the plane. The soil sampling depth of the outer well hole is lower than that of the inner well hole, and the depth difference satisfies ; Plastic zone ratio index The range is .

6. A large-scale caisson soil extraction control method based on soil critical state according to claim 1, characterized in that: The steps of judging whether the construction scheme meets the safety and stability requirements of the caisson sinking state include: The distribution of the plastic zone in the blade foot contact area is calculated by numerical model, and the area of ​​the plastic zone is obtained. Total contact area with blade foot , calculate the plastic zone ratio index , to determine whether it meets the set range, the formula is: ; Determine the number of continuous failure paths in the plastic zone through connectivity analysis of the plastic zone in the numerical model , when the preset requirements are met, it means that sufficient penetration failure paths are formed; like and If all requirements are met, the construction plan is judged to be able to ensure the safe and stable sinking of the caisson; otherwise, the construction plan is adjusted and re-verified.

7. A large-scale caisson soil extraction control method based on soil critical state according to claim 1, characterized in that: The adjustment of the construction plan includes the following steps: When the model calculation results show that the plastic zone ratio index does not meet the reasonable distribution range, the ratio of soil extraction from the inner well hole and the outer well hole is adjusted, the soil extraction from the inner well hole is increased or decreased, and the soil extraction depth difference of the outer well hole is adjusted simultaneously; When the connectivity index of the plastic zone does not meet the requirements, the soil sampling sequence is adjusted to give priority to the inner borehole area and gradually expand to the outer borehole area; If uneven force is applied to the blade foot area, resulting in a tilting trend, the force on one side of the soil can be reduced by adjusting the amount of soil taken in the tilting direction, and the soil taking range on the opposite side can be increased to balance the force. After each adjustment, the distribution and connectivity of the plastic zone are re-verified, and adjustments are made cyclically until the construction plan meets the safety and stability requirements of the caisson sinking state.

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