CN-121980121-A - Method and system for predicting shrinkage cavity space-time change rule of compaction pile

CN121980121ACN 121980121 ACN121980121 ACN 121980121ACN-121980121-A

Abstract

The application discloses a method and a system for predicting a space-time change rule of shrinkage holes of compaction piles, and relates to the technical field of foundation treatment and geotechnical engineering; the method comprises the steps of establishing a functional relation of peak cohesive force, peak internal friction angle, residual cohesive force and residual internal friction angle relative to water content based on test data, establishing a softening constitutive relation of strength evolving from peak to residual according to accumulated plastic shear strain, determining far-field lateral stress by combining depth, soil weight and static soil pressure coefficients, constructing a three-partition stress field of a residual area, a softening area and an elastic area around a pile hole according to the far-field lateral stress, further constructing a system shrinkage factor according to a stress state at a hole wall and a viscoplastic strain rate relation, establishing an evolution equation of hole radius relative to time, depth and water content, and calculating a change result of the pile hole radius with time and depth in a target period according to the evolution equation. The method realizes the unified calculation of the shrinkage cavity process under the combined action of multiple factors.

Inventors

WANG XIN
HAN XIDONG
ZHANG HANG
REN XIUFANG

Assignees

陕西天地地质有限责任公司
陕西省煤田地质集团有限公司

Dates

Publication Date: 20260505
Application Date: 20260407

Claims (10)

1. A method for predicting the shrinkage cavity space-time change rule of an compaction pile is characterized by comprising the following steps: obtaining the depth of a pile hole to be detected, the radius of an initial hole, the soil body weight, the static soil pressure coefficient, the water content and shear strength test data; according to the shear strength test data, establishing a functional relation of peak cohesion, peak internal friction angle, residual cohesion and residual internal friction angle respectively with respect to water content; Establishing a softening constitutive relation evolving from a peak strength parameter to a residual strength parameter according to the accumulated plastic shear strain; Determining far-field lateral stress according to the depth, the soil body weight and the static soil pressure coefficient, and establishing a three-zone stress field of a residual zone, a softening zone and an elastic zone around the pile hole by combining the softening constitutive relation; constructing a system shrinkage factor according to the relation between the stress state at the hole wall and the viscoplastic strain rate, and establishing an evolution equation of the hole radius with respect to time, depth and water content; And solving the change result of the pile hole radius along with time and depth in the target period according to the evolution equation.
2. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 1, wherein the method comprises the steps of, The shear strength test data comprise triaxial shear test data and annular shear test data under different water content conditions; The triaxial shear test data correspond to the determination of peak cohesive force and peak internal friction angle, and the annular shear test data correspond to the determination of residual cohesive force and residual internal friction angle; and respectively fitting the peak intensity parameter and the residual intensity parameter obtained under each water content into continuous functions, and taking the continuous functions as the unified input parameters of the follow-up softening constitutive relation and the three-partition stress field.
3. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 2, wherein the method comprises the steps of, The softening constitutive relation takes accumulated plastic shear strain as an evolution variable, the current cohesive force is expressed as a continuous transition quantity between the residual cohesive force and the peak cohesive force, the current internal friction angle is expressed as a continuous transition quantity between the residual internal friction angle and the peak internal friction angle, and the continuous transition quantity is controlled by softening modulus and monotonically converges to the residual strength parameter along with the increase of the accumulated plastic shear strain.
4. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 3, wherein the method comprises the following steps of, The stress field of the three subareas is established through an axisymmetric round hole balance relation, and the stress field is divided into a residual area adjacent to the hole wall, a softening area positioned outside the residual area and an elastic area positioned outside the softening area in sequence along the radial direction of the pile hole; And respectively applying a radial stress continuous condition and a hoop stress continuous condition at the junction of the residual region and the softening region and the junction of the softening region and the elastic region, and representing the evolution of the hole circumferential stress field along time according to the corresponding relation between the junction radius of each region and the current hole radius.
5. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 4, wherein the method comprises the steps of, The far-field lateral stress is determined by depth, soil body weight and static soil pressure coefficient together and is input as the outer boundary of the three-zone stress field; the stress state at the hole wall is determined by the radial stress and the hoop stress of the three-partition stress field at the current hole radius, and the stress state at the hole wall and the current strength parameter jointly determine the yield state at the hole wall and serve as input quantity for constructing the viscoplastic strain rate relation.
6. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 5, wherein the method comprises the steps of, The viscoplastic strain rate relation is expressed by adopting a combination of super-yield driving force, a fluidity parameter, a rheological stress index and a time attenuation index, wherein the super-yield driving force is determined by the difference between the partial stress at the hole wall and the current yield strength at the hole wall, the fluidity parameter is a function of water content, the rheological stress index represents the nonlinear influence of the super-yield driving force on the strain rate, and the time attenuation index represents the attenuation law of the aperture shrinkage rate along with time.
7. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 6, wherein the method comprises the steps of, Constructing a system shrinkage cavity coefficient according to the fluidity parameter, the far-field lateral stress, the residual strength scale and the rheological stress index, and incorporating a stress conversion term at the hole wall into the system shrinkage cavity coefficient; The system shrinkage cavity coefficient, the current hole radius and the time attenuation term jointly form a hole radius evolution equation, and the hole radius evolution equation is solved by taking an initial hole radius and an initial time as initial conditions.
8. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 7, wherein the method comprises the steps of, And obtaining an explicit hole radius time-course expression after solving the hole radius evolution equation, inputting the depth, the water content, the initial hole radius and the starting time corresponding to any pile hole to be tested, calling a peak intensity parameter function, a residual intensity parameter function, a softening constitutive relation and a system shrinkage factor, calculating the hole radius at each time in a target period, and forming a data sequence of the change of the hole radius along with time and depth.
9. The method for predicting the shrinkage cavity space-time variation law of the compaction pile according to claim 8, further comprising the step of parameter inversion: And the parameter inversion step takes the actual measurement hole radius time course of the field monitoring hole as observation data, takes the sum of squares of residual errors between the theoretical calculation hole radius time course and the actual measurement hole radius time course as an objective function, carries out iterative solution on comprehensive coefficients in a flow parameter function coefficient, a rheological stress index, a time attenuation index and a system shrinkage cavity coefficient, and replaces an inversion result to the hole radius evolution equation.
10. The utility model provides a compaction stake shrinkage cavity space-time change rule prediction system which characterized in that includes: the data acquisition module is used for acquiring the depth of the pile hole to be detected, the initial hole radius, the soil body weight, the static soil pressure coefficient, the water content and the shear strength test data; The intensity parameter establishing module is used for establishing a functional relation of peak cohesive force, peak internal friction angle, residual cohesive force and residual internal friction angle respectively with respect to the water content according to the shear strength test data; The softening cost building module is used for building a softening cost structure relation evolving from a peak strength parameter to a residual strength parameter according to the accumulated plastic shear strain; the stress field construction module is used for determining far-field lateral stress according to the depth, the soil body weight and the static soil pressure coefficient, and establishing a three-partition stress field of a residual area, a softening area and an elastic area around the pile hole by combining the softening constitutive relation; The shrinkage cavity coefficient and evolution equation construction module is used for constructing a system shrinkage cavity coefficient according to the stress state and the viscoplastic strain rate relation at the hole wall and establishing an evolution equation of the hole radius with respect to time, depth and water content; and the evolution calculation module is used for calculating the change result of the pile hole radius along with time and depth in the target period according to the evolution equation.

Description

Method and system for predicting shrinkage cavity space-time change rule of compaction pile Technical Field The application relates to the technical field of foundation treatment and geotechnical engineering, in particular to a method and a system for predicting a shrinkage cavity space-time change rule of a compaction pile. Background The compaction pile treatment technology is widely applied to foundation reinforcement engineering in loess areas. In the actual construction process, a certain time interval is usually reserved between the pile hole forming and the packing tamping, and hole wall soil is influenced by hole forming unloading, in-situ stress redistribution and water condition change, so that shrinkage hole phenomena with different degrees are easy to occur. The shrinkage cavity can change the aperture size and the stable state of the hole wall, so that the subsequent filling amount, tamping construction and pile body forming quality are affected, and therefore, the aperture change rule after the compaction pile is formed is necessary to be analyzed and predicted. In the existing engineering analysis, for the shrinkage problem of the compaction pile, an empirical judgment method, an on-site observation method or a simplified static analysis method is mostly adopted. Although the method can reflect the shrinkage cavity phenomenon under the local working condition, the depth change, the water content difference and the continuous deformation characteristic of the pore-forming after the pore-forming are difficult to consider simultaneously. In particular to a yellow soil body, the shear strength is obviously influenced by the water content, and the soil body around the hole can undergo the process of evolving from peak strength to residual strength after unloading, and the actual stress and deformation state of the soil body near the hole wall are difficult to accurately describe only by adopting stress analysis of fixed strength parameters or single moment. In addition, the existing method is still not systematic enough for researching the relationship between the partition state of the soil body around the hole, the stress state at the hole wall and the shrinkage rate, and lacks a prediction method for unifying the relative strength parameters of the water content, the strength softening process, the distribution of the stress around the hole and the time-varying shrinkage rule. Therefore, under different burial depths, water contents and waiting time, the calculation result of the shrinkage cavity amount often has larger uncertainty, and the stability foundation is difficult to provide for construction organization and process control. Therefore, a prediction method for the shrinkage cavity space-time change rule of the compaction pile, which can comprehensively consider the moisture content, the strength evolution after unloading and time factors, is needed. Disclosure of Invention The embodiment of the application provides a method and a system for predicting a shrinkage cavity space-time change rule of a compaction pile, which are used for at least solving part of technical problems in the related art. According to a first aspect of the embodiment of the application, a method for predicting a shrinkage cavity space-time change rule of a compaction pile is provided, which comprises the following steps: obtaining the depth of a pile hole to be detected, the radius of an initial hole, the soil body weight, the static soil pressure coefficient, the water content and shear strength test data; according to the shear strength test data, establishing a functional relation of peak cohesion, peak internal friction angle, residual cohesion and residual internal friction angle respectively with respect to water content; Establishing a softening constitutive relation evolving from a peak strength parameter to a residual strength parameter according to the accumulated plastic shear strain; Determining far-field lateral stress according to the depth, the soil body weight and the static soil pressure coefficient, and establishing a three-zone stress field of a residual zone, a softening zone and an elastic zone around the pile hole by combining the softening constitutive relation; constructing a system shrinkage factor according to the relation between the stress state at the hole wall and the viscoplastic strain rate, and establishing an evolution equation of the hole radius with respect to time, depth and water content; And solving the change result of the pile hole radius along with time and depth in the target period according to the evolution equation. As an alternative, the shear strength test data comprises triaxial shear test data and annular shear test data under different water content conditions; The triaxial shear test data correspond to the determination of peak cohesive force and peak internal friction angle, and the annular shear test data correspond to the determination of residual cohesive f