Search

CN-121996963-A - Unsaturated sand roadbed filler permanent deformation prediction model and establishment method thereof

CN121996963ACN 121996963 ACN121996963 ACN 121996963ACN-121996963-A

Abstract

The invention discloses a permanent deformation prediction model of unsaturated sand subgrade filler and a building method thereof, wherein the building method comprises the steps of preparing sand meeting the grading requirement of a highway subgrade to prepare a sand sample; the method comprises the steps of measuring permanent deformation curves of sand samples under different matrix suction forces, different net confining pressures, different dynamic stress amplitudes and different compactibility through experiments, introducing matrix suction force and compactibility influence factors into a basic frame by using a Karg model, establishing a prediction model for coupling the matrix suction forces, the net confining pressures, the dynamic stress amplitudes and the compactibility simultaneously, and calibrating model parameters by adopting a normalized main curve method to obtain an improved permanent deformation prediction model. The invention can accurately capture the permanent deformation of the unsaturated sand roadbed filler under different matrix suction forces, different net confining pressures, different dynamic stress amplitudes and different compactibility, realizes the unified description of span stress, span suction force, span state and span soil class, and is convenient for engineers to understand and apply to actual design.

Inventors

  • ZHANG CHUANG
  • ZHANG JUNHUI
  • YIN HONGFEI

Assignees

  • 长沙理工大学

Dates

Publication Date
20260508
Application Date
20260123

Claims (9)

  1. 1. The method for establishing the unsaturated sand subgrade filler permanent deformation prediction model is characterized by comprising the following steps of: S1, preparing sand meeting the grading requirement of a highway subgrade to prepare a sample; s2, measuring permanent deformation curves of the sand sample under different matrix suction forces, different net confining pressures, different dynamic stress amplitudes and compactness through experiments; S3, taking a Karg model as a basic frame, introducing matrix suction and compactness influencing factors, and establishing a prediction model for simultaneously coupling the matrix suction, net confining pressure, dynamic stress amplitude and compactness; And S4, calibrating model parameters by adopting a normalized curve method, and compressing the accumulated strain curves under different working conditions into a unique dimensionless main curve.
  2. 2. The method for establishing the unsaturated sand subgrade filler permanent deformation prediction model according to claim 1, wherein in the step S2, the permanent deformation curves of the sand samples under different matrix suction forces, different net confining pressures, different dynamic stress amplitudes and different compactibility are measured through a GDS unsaturated triaxial test system.
  3. 3. The method for building a prediction model of permanent deformation of unsaturated sand subgrade filler according to claim 1, in which said S3 comprises the steps of: the expression of the axial cumulative strain with respect to the number of cycles N based on the Karg model is shown in the formula (1), (1) Wherein c 1 、c 2 、c 3 is a constant parameter; Is axial strain, N is cyclic loading times, The two sides of the formula (1) can be obtained by respectively deriving N about the cyclic vibration times: (2) Considering that the plastic deformation of the soil mass in the stable phase is far smaller than the compression deformation in the initial stage of the test, karg et al neglect the term c 3 N in the formula (1), it is possible to obtain: (3) And (3) in the combined type, eliminating the cyclic loading times N in the two formulas, and obtaining the expression of the axial accumulated strain rate as follows: (4) the formula (4) is simplified as: (5) Wherein alpha f and theta f are parameters describing the axial accumulated strain rate in an initial stage, and beta f is a parameter describing the axial accumulated strain rate entering a stable deformation stage; assuming that the plastic deformation curve of the soil body is in different stress states And (3) with The ratio between the accumulated axial strain of the soil body and the reference accumulated axial strain is constant, and the function expression of the accumulated axial strain of the soil body relative to the reference accumulated axial strain can be: (6) Wherein sigma n is net confining pressure, q ampl is dynamic stress amplitude, s is matrix suction force, and K is compactness; Respectively is Is used as a reference value for the (c), Is that Cumulative axial strain under conditions, f σ is a function about σ n to account for the effects of net confining pressure, f q is a function about q ampl to account for the effects of dynamic stress amplitude, f s is a function about s to account for the effects of substrate suction, f K is a function about K to account for the effects of compaction; The expression of the function f σ 、f q 、f s 、f k is as follows: (7) (8) (9) (10) Wherein: in order to refer to the net confining pressure, For reference to the magnitude of the dynamic stress, For reference to the suction force of the substrate, As reference compactibility, a, b, m, n, k 1 、k 2 are model parameters respectively; Deriving the formula (6): (11) substituting formula (5) into formula (11) to obtain: (12) Wherein: , , a constant related to the axial cumulative deformation; substituting formula (6) into formula (12): (13) the corresponding terms of the left and right sides of the equation (13) are equal to each other and can be obtained: (14) (15) (16) The improved Karg model expression for the integration of the number of loops N on both sides of equation (12) is: (17)。
  4. 4. The method for building a prediction model of permanent deformation of unsaturated sand subgrade filler according to claim 1, characterized in that in S4, the net confining pressure is normalized, and the parameters a: Determining a parameter a in a net confining pressure influence factor f σ , selecting test data for calibration, fixing f q 、f s and f K unchanged, only changing f σ , wherein f N is a function for representing the influence of cyclic loading times, and setting reference strain The expression is as follows: (18) Thus, the expression of the axial cumulative strain can be written as follows: (19) Substituting formula (7) into formula (19) to obtain: (20) Fitting the test data by equation (20) yields parameter a.
  5. 5. The method for building a permanent deformation prediction model of unsaturated sand subgrade filler according to claim 1, characterized in that in S4, the dynamic stress amplitude is normalized, and the parameter b is calibrated: Determining parameter b in dynamic stress amplitude influencing factor f q , selecting test data for calibration, fixing f σ 、f s and f K unchanged, only changing f q , and setting reference strain The expression is as follows: (21) Thus, the expression of the axial cumulative strain can be written as follows: (22) Bringing equation (8) into (22) yields: (23) Fitting the test data by equation (23) yields parameter b.
  6. 6. The method for building a prediction model of permanent deformation of unsaturated sand subgrade filler according to claim 1, wherein in S4, the matrix suction force is normalized, and the parameters m and n are calibrated: Determining parameters m and n in matrix suction influence factor expression f s , selecting test data for calibration, fixing f σ 、f q and f K unchanged, only changing f s , and setting reference strain The expression is as follows: (24) Thus, the expression of the axial cumulative strain can be written as follows: (25) substituting formula (10) into formula (25): (26) fitting the test data by equation (26) yields parameters m and n.
  7. 7. The method for building a permanent deformation prediction model of unsaturated sand subgrade filler according to claim 1, wherein in S4, the compaction degree is normalized, and the calibration parameters k 1 and k 2 are: Determining parameters k 1 and k 2 in a compactness influence factor expression f K , selecting test data for calibration, fixing f σ 、f q and f s unchanged, only changing f K , setting reference strain The expression is as follows: (27) Thus, the expression of the axial cumulative strain can be written as follows: (28) Substituting formula (10) into formula (28): (29) The parameters k 1 and k 2 were obtained by fitting the experimental data by equation (29).
  8. 8. The method for constructing a model for predicting permanent deformation of an unsaturated sand subgrade filler according to claim 1, characterized in that in S4, the parameters of formula (17) are 、 、 Calibrating: from equation (6), the reference axial cumulative strain The expression of (c) can be written as: (30) fitting the axial cumulative strain by (17) Curve to obtain model parameters , , 。
  9. 9. An unsaturated sand subgrade filler permanent deformation prediction model, which is characterized by being obtained by the method for establishing the unsaturated sand subgrade filler permanent deformation prediction model according to claim 1.

Description

Unsaturated sand roadbed filler permanent deformation prediction model and establishment method thereof Technical Field The invention belongs to the technical field of road engineering, and relates to a non-saturated sand subgrade filler permanent deformation prediction model and an establishment method thereof. Background With the rapid development of the transportation infrastructure in China, the expressway and municipal road engineering have higher requirements on the safety, durability and service performance of roadbeds. Under the action of long-term traffic circulating load, roadbeds are easy to generate diseases such as sedimentation, uneven deformation, ruts and the like, and the diseases can gradually aggravate and influence the structural integrity of the pavement, thereby seriously threatening the safe operation and the service life of the highway. In actual engineering, roadbed soil is often in an unsaturated state, and the existence of matrix suction changes the effective stress state of soil body, so that the permanent deformation characteristic of roadbed is obviously influenced. Meanwhile, the compactness is used as a core index for roadbed construction quality control, the compactness, pore structure and mechanical property of a soil body are directly determined, the deformation resistance of unsaturated sand soil can be obviously changed, when the compactness is insufficient, the soil body is large in porosity and weak in inter-particle connection, particle rearrangement and plastic accumulation are easy to occur under the action of cyclic load, the permanent deformation development is accelerated, and when the compactness is too high, the soil body structure is possibly damaged, the long-term stability of the roadbed is also not facilitated, so that the compactness and the matrix suction form key factors affecting the permanent deformation of the unsaturated sand roadbed together. In the prior art, roadbed permanent deformation prediction models are mostly based on complex mechanical frames such as viscoplastic theory, fractional order constitutive or envelope surface plasticity, and the like, and the problems of complex model form, multiple parameters, low calculation efficiency and the like exist, so that the requirements of rapid prediction and construction guidance of engineering sites are difficult to meet. More importantly, most models are only suitable for deformation prediction under saturated soil or small cycle times, not only neglect the regulation and control effect of matrix suction on the effective stress and deformation characteristics of the soil, but also do not fully consider the influence of compactness on the pore structure and particle occlusion effect of unsaturated sand, and the deformation evolution rule of the unsaturated sand subgrade under long-term traffic cyclic load under different compactibility conditions cannot be accurately described. In addition, the universality of the existing model is poor, uniform prediction of the stress level, the suction force, the soil state and the soil state is difficult to consider, and the model is particularly difficult to provide reliable basis for roadbed construction quality control, service performance assessment and disease prevention due to larger limitation of the model in practical engineering application because deformation prediction requirements under different compactness working conditions cannot be adapted. In conclusion, the existing roadbed permanent deformation prediction model has the problems of complex form, narrow application range, insufficient consideration of key influencing factors (especially the synergistic effect of compactness and matrix suction), insufficient prediction precision and universality and the like, and brings a plurality of inconveniences to practical engineering application. Therefore, there is a need to develop a compact, efficient, highly accurate, portable, and fully coupled method for predicting permanent deformation of an unsaturated sand subgrade that is affected by compaction and matrix suction. Disclosure of Invention In order to solve the problems, the invention provides a model for predicting the permanent deformation of the unsaturated sand subgrade filler, which can accurately capture the permanent deformation of the unsaturated sand subgrade filler under different matrix suction forces, different net confining pressures, different dynamic stress amplitudes and different compactibility, realizes the unified description of cross-stress, cross-suction forces, cross-state and cross-soil types, and is convenient for engineers to understand and apply to actual design. The invention further aims at a method for establishing the unsaturated sand roadbed filler permanent deformation prediction model. The technical scheme adopted by the invention is that the method for establishing the unsaturated sand subgrade filler permanent deformation prediction model comprises the followin