Layered frozen soil unfreezing and consolidation prediction method, storage medium and equipment

Abstract

The invention discloses a layered frozen soil unfreezing and consolidation prediction method. The method comprises the following steps: step 1, obtaining related parameters of layered frozen soil; 2, solving the unfreezing and consolidation pore pressure distribution model of the layered frozen soil in the seasonal frozen region to obtain a pore pressure distribution relational expression of the unfreezing region; and step 3, solving the consolidation ratio of unfreezing consolidation of the layered frozen soil in the seasonal frozen area. The invention further discloses a storage medium, and the storage medium stores a computer program used for executing the method. The invention also provides an apparatus comprising a memory storing a computer program for performing the aforementioned method, and a processor. According to the invention, the influence mechanism of the initial transient pressure and the heat source unfreezing coefficient on the layered frozen soil unfreezing consolidation pore water pressure distribution can be disclosed, and the heat source unfreezing coefficient most suitable for different soil structures is explored while the consolidation efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of frozen soil thawing and consolidation, and in particular relates to a layered frozen soil thawing and consolidation prediction method, storage medium and equipment. Background Art

[0002] Frozen soil refers to the phenomenon that water in the soil freezes under low temperature conditions. Frozen soil areas account for about 20% of the earth's land area, mainly distributed in high latitudes and high altitudes. These areas have a significant impact on global climate change, ecosystems and human activities due to their unique climate and geological conditions. First of all, frozen soil is very harmful to buildings. Studies have shown that the frost heave force of frozen soil poses a great threat to buildings. With the change of seasonal temperature, the expansion and contraction of frozen soil volume causes damage to the basic structure of buildings. Coupled with the degradation of frozen soil caused by climate warming, the problem has become more and more serious, especially in high latitudes and high altitudes. In addition, plateau frozen soil areas are very sensitive to climate change. Studies have shown that with the rise in global temperatures, plateau permafrost is undergoing significant degradation, which has not only affected the local ecological environment, but also brought considerable challenges to human society. It also brings new challenges to the safe operation of roads. Therefore, studying the impact of climate change on the stability of frozen soil and formulating corresponding response strategies have become the most urgent issues at present. The long-term impact of roadbed engineering behavior on frozen soil in high altitude areas is a complex problem. Long-term monitoring data show that engineering structures such as railways and highways significantly affect the temperature field of frozen soil, causing the upper limit of frozen soil to decrease and the thickness of the active layer to increase. The stability of engineering structures will be affected by these changes, and the risk of roadbed diseases will also increase. Therefore, in order to ensure the long-term safety of transportation infrastructure, it is crucial to conduct in-depth research on the impact of engineering behavior on frozen soil.

[0003] Since the existing layered soil consolidation prediction method has not yet taken into account the thawing consolidation of frozen soil, the existing frozen soil consolidation model lacks consideration of the heterogeneity of the soil and the influence of its own weight, which leads to huge errors between the prediction results and the actual situation. Therefore, it is necessary to design a new prediction method for the thawing consolidation of layered frozen soil. Summary of the invention

[0004] The purpose of the present invention is to provide a method, storage medium and device for predicting the thawing and consolidation of layered frozen soil, so as to solve the problem that the existing layered soil consolidation prediction method proposed in the background technology has not yet taken into account the thawing and consolidation of frozen soil, and the existing frozen soil consolidation model lacks consideration of the heterogeneity of the soil and the influence of its own weight, which results in huge errors between the prediction results and the actual situation.

[0005] To achieve the above object, the present invention provides a method for predicting thawing and consolidation of layered frozen soil, comprising the following steps:

[0006] Step 1: Obtaining relevant parameters of layered frozen soil;

[0007] Step 2: Solve the pore pressure distribution model of thawing and consolidation of layered frozen soil in seasonally frozen areas to obtain the pore pressure distribution relationship in the thawing area; specifically, the steps include:

[0008] The first step is to input the external influencing parameters required by the model;

[0009] The second step is to construct boundary condition equations. Based on the different positions of the thaw line in the soil layer, the thaw line is defined as the first stage when it is at the top layer, and as the second stage when it is at the bottom layer. The bottom boundary conditions of the first stage and the second stage are obtained by solving the external influencing parameters and layered frozen soil related parameters in the first step. The top boundary conditions are defined based on the completely permeable interface in Terzaghi's theorem.

[0010] The third step is to obtain the general solutions of the excess pore water pressure in the first and second stages of the model based on the control equation of soil consolidation and the Gaussian error function.

[0011] Step 4: Based on the general solution of the first stage obtained in the third step and combined with the bottom boundary conditions and top boundary conditions of the first stage, the pore pressure distribution of the single-layer soil thawing consolidation in the first stage is obtained, and the initial conditions of the bottom layer in the second stage are obtained according to the bottom pore pressure at the end point of the first stage of pore pressure;

[0012] Step 5: Based on the general solution of the pore pressure of the bottom soil in the second stage obtained in the third step and combined with the bottom boundary conditions of the second stage and the initial conditions of the second stage obtained in the fourth step, the distribution of the pore pressure of the bottom soil in the second stage is obtained; then, according to the Schiffman continuity condition, the top boundary condition and the general solution of the pore pressure of the top soil in the second stage, the distribution of the pore pressure of the top soil in the second stage is obtained;

[0013] Step 3: Calculate the consolidation ratio of thawing and consolidation of layered frozen soil in seasonally frozen areas:

[0014] Substitute the excess porosity pore pressure distribution obtained in the first and second stages in step 2 into the consolidation ratio solution formula respectively, and then obtain the consolidation ratio prediction structure of each stage, and compare the prediction results with the actual engineering requirements. If the engineering requirements are not met, return to the first step in step 2 to reset the external conditions until the engineering requirements are met.

[0015] In a specific embodiment, the layered frozen soil related parameters include the thickness, permeability, volume compression coefficient, and saturated density of different soil layers.

[0016] In a specific embodiment, the layered frozen soil related parameters also include the movement of the thawing line S(t), and the consolidation coefficients of the top soil and the bottom soil.

[0017] In a specific implementation, the external influencing parameters include a thawing coefficient of a thawing heat source and an initial external transient pressure.

[0018] In a specific embodiment, in step 3, the first stage consolidation ratio obtained is:

[0019]

[0020] The consolidation ratio of the second stage is obtained as:

[0021]

[0022] The present invention also provides a storage medium storing a computer program, wherein the computer program is suitable for being loaded by a processor and executing the above-mentioned layered frozen soil thawing and consolidation prediction method.

[0023] The present invention also provides a device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the layered frozen soil thawing and consolidation prediction method as described above is run.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention comprehensively considers the initial transient pressure, the thickness of different soil layers after stratification of layered soil, the permeability coefficient, the volume coefficient and the saturated density, and the thawing coefficient of the thawing heat source, and can reveal the influence mechanism of the initial transient pressure and the thawing coefficient of the heat source on the distribution of pore water pressure of thawing consolidation of layered frozen soil, while improving the consolidation efficiency and exploring the most suitable heat source thawing coefficient for different soil structures.

[0026] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention is further described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0028] Figure 1 It is a flow chart of a method for predicting thawing and consolidation of layered frozen soil according to the present invention;

[0029] Figure 2 is a schematic diagram of a layered frozen soil thawing model in one embodiment of the present invention;

[0030] Figure 3 It is a schematic diagram of model rationality verification of consolidation ratio in one embodiment of the present invention;

[0031] Figure 4 It is a schematic diagram of the rationality verification of the model of excess pore water pressure distribution in one embodiment of the present invention;

[0032] Figure 5 Schematic diagram of the difference in pore pressure prediction distribution between the homogeneous frozen soil model and the heterogeneous frozen soil model in the present invention;

[0033] Figure 6 It is a schematic diagram of the change of consolidation ratio of different models in the present invention with the thawing coefficient. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] See also Figure 1 The present invention provides a method for predicting the thawing and consolidation of layered frozen soil. The frozen soil is composed of two layers of soil with completely different properties. The top layer has a limited thickness and the bottom layer is a semi-infinite space. The Neumann phase change heat conduction model, Terzaghi consolidation theory and layered soil consolidation theory are used. The migration of water during the consolidation process conforms to Darcy's law. The thawed soil is saturated soil (without considering the influence of air). The consolidation control equation is assumed based on the Gaussian error function. The bottom boundary condition is obtained based on the thawing rate of the thawing front and the consolidation coefficient of the soil, thereby obtaining an analytical solution for the pore pressure distribution and establishing a layered frozen soil thawing model. Specifically, the following steps are included:

[0036] Step 1: Obtain relevant parameters of layered frozen soil.

[0037] The relevant parameters of layered frozen soil include the thickness, permeability, volume compression coefficient and saturated density of different soil layers.

[0038] Step 2: Solve the pore pressure distribution model of thawing and consolidation of layered frozen soil in seasonally frozen areas to obtain the pore pressure distribution relationship in the thawing area; specifically, the steps include:

[0039] The first step is to input the external influencing parameters required by the model, including: the thawing coefficient of the thawing heat source and the initial external transient pressure;

[0040] The second step is to construct boundary condition equations. Based on the external influencing parameters of the first step and the relevant parameters of the soil, the bottom boundary conditions of the first stage and the second stage are obtained by solving them. The top boundary conditions are defined based on the fully permeable interface in Terzaghi's theorem.

[0041] The third step is to obtain the general solutions of the excess pore water pressure in the first and second stages of the model based on the control equation of soil consolidation and the Gaussian error function.

[0042] Step 4: Based on the general solution of the first stage obtained in the third step and combined with the bottom boundary conditions and top boundary conditions of the first stage, the pore pressure distribution of the single-layer soil thawing consolidation in the first stage is obtained, and the initial conditions of the second stage are obtained according to the bottom pore pressure at the end point of the first stage of air compression;

[0043] Step 5: Based on the general solution of the pore pressure of the bottom soil in the second stage obtained in the third step and combined with the bottom boundary conditions of the second stage and the initial conditions of the second stage obtained in the fourth step, the distribution of the pore pressure of the bottom soil in the second stage is obtained; then, according to the Schiffman continuity condition, the top boundary condition and the general solution of the pore pressure of the top soil in the second stage, the distribution of the pore pressure of the top soil in the second stage is obtained;

[0044] Step 3: Calculate the consolidation ratio of thawing and consolidation of layered frozen soil in seasonally frozen areas:

[0045] Substitute the excess porosity pore pressure distribution obtained in the first and second stages in step 2 into the consolidation ratio solution formula respectively, and then obtain the consolidation ratio prediction structure of each stage, and compare the prediction results with the actual engineering requirements. If the engineering requirements are not met, return to the first step in step 2 to reset the external conditions until the engineering requirements are met.

[0046] Example 1

[0047] A method for predicting thawing and consolidation of layered frozen soil comprises the following steps:

[0048] Step 1: Obtain relevant parameters of layered frozen soil based on soil survey results, including thickness, permeability, volume compression coefficient, and saturated density of different soil layers.

[0049] Layered frozen soil is composed of two layers of soil with completely different properties. The top layer of soil is of limited thickness, while the bottom layer of soil is a semi-infinite space.

[0050] There is a heat source. The solution to the heat conduction problem was proposed by Newumann. The motion of the thawing line S(t) is given by:

[0051]

[0052] Among them, α is the thawing coefficient determined in the solution of the heat conduction problem, S(t) is the distance from the soil surface to the thaw surface, and t is the time.

[0053] Then the consolidation coefficient of each layer can be obtained through the permeability coefficient and volume compression coefficient:

[0054]

[0055] Among them, k v1 , k v2 Represent the permeability coefficient of the top soil and bottom soil, m v1 、mv2 Represent the volume compression coefficient of the top soil and bottom soil, C v1 , C v2 denote the consolidation coefficients of the top and bottom soils, respectively, w Indicates the weight of water.

[0056] Step 2: Solve the pore pressure distribution model of thawing and consolidation of layered frozen soil in seasonally frozen areas.

[0057] The first step is to input the external influencing parameters required by the model, including: the thawing coefficient of the thawing heat source and the initial external transient pressure.

[0058] The second step is to construct boundary condition equations. Since the thaw line is located in different soil layers, the thaw line is defined as the first stage when it is at the top layer and as the second stage when it is at the bottom layer. The bottom boundary conditions of the first stage and the second stage are obtained based on the external influencing parameters and the relevant parameters of the layered frozen soil; the top boundary conditions are defined based on the fully permeable interface in the Terzaghi theorem.

[0059] The top boundary condition relationship is:

[0060] u1(0,t)=0,t>0Formula (3)

[0061] The specific method for solving the bottom boundary conditions is as follows:

[0062] At the thaw line, the ice in the frozen soil is melted and the melted water is released; under the combined action of transient pressure and self-weight, the water flows upward. For saturated soil consolidation, the boundary condition here is that any flow out of the thaw line is replaced by the change in soil volume. According to Darcy's law, as the thaw line advances, the volume of pore fluid discharged from the bottom boundary with the increase of time is:

[0063]

[0064] Where u1 and u2 are the excess pore water pressures of the top and bottom soils, respectively, and A R is the cross-sectional area of ​​the soil element. The volume change ΔV is also equal to the volume change of a layer with a thickness of ΔS(t), and the volume strain is:

[0065]

[0066] The volumetric strain of compressible soil is:

[0067]

[0068] Among them, Δσ i '(z,t) is the effective stress difference.

[0069] In equations (4) to (6), i refers to the position of the layer where the thaw line is located. When i=1, the thaw line is located in the top layer of soil; when i=2, the thaw line is located in the bottom layer of soil.

[0070] Therefore, the bottom boundary conditions of the two stages are:

[0071] Phase 1:

[0072] Phase 2:

[0073] Where h1 is the thickness of the top soil.

[0074] In the third step, based on the control equation of soil consolidation and the Gaussian error function, the general solutions of the excess pore water pressure in the first and second stages of the model are obtained respectively.

[0075] The governing equation for thawing consolidation in the first stage is:

[0076]

[0077] In the second stage:

[0078]

[0079] Among them, z is the depth and P0 is the transient pressure. Then, based on the consolidation equation and Gaussian error equation, a two-stage general solution is obtained. In the first stage:

[0080]

[0081] Among them, A, B, and C are relevant assumption parameters.

[0082] In the second stage:

[0083]

[0084] Among them, A1, B1, C1, A2, B2, and C2 are relevant assumption parameters.

[0085] The fourth step is to obtain the general solution of the first stage obtained in the third step and the bottom boundary conditions and top boundary conditions of the first stage to obtain the pore pressure distribution of the single-layer soil thawing consolidation in the first stage, and obtain the initial conditions of the second stage according to the bottom pore pressure at the end point of the first stage of pore pressure.

[0086] The first stage general solution related parameters A, B, and C are:

[0087]

[0088] C=0 Formula (17)

[0089] in,

[0090] And obtain the bottom initial conditions of the second stage:

[0091]

[0092] The fifth step is to obtain the pore pressure relationship of the bottom soil in the second stage based on the general solution of the pore pressure of the bottom soil in the third step, combined with the bottom boundary conditions of the second stage and the initial conditions of the second stage obtained in the fourth step; then, the pore pressure relationship of the top soil in the second stage is obtained according to the Schiffman continuity condition, the top boundary condition and the general solution of the pore pressure of the bottom soil in the second stage.

[0093] The relevant parameters A2, B2, and C2 of the second-stage bottom soil pore pressure solution are obtained as follows:

[0094]

[0095] in, According to the Schiffman continuity condition:

[0096] u1(h1,t)=u2(h1,t) Formula (24)

[0097]

[0098] The relevant parameters A1, B1, and C1 of the second stage top soil pore pressure solution are obtained as follows:

[0099]

[0100]

[0101] C1=0 Formula (28)

[0102] Step 3: Substitute the excess porosity pore pressure distribution obtained in the first stage and the second stage into the consolidation ratio solution formula respectively, and then obtain the consolidation ratio prediction results of each stage, and compare the prediction results with the actual engineering requirements. If the engineering requirements are not met, return to step 2 to set the external conditions until the engineering requirements are met.

[0103] The consolidation ratio U1 of the first stage and the consolidation ratio U2 of the second stage are calculated by Stieltjes integral:

[0104]

[0105]

[0106] The present invention sets the good consolidation ratio to 0.8, so when U>0.8, the thawing consolidation engineering effect is good; when U≤0.8, the thawing consolidation effect is poor, and the external parameters need to be changed until U>0.8.

[0107] This embodiment also provides a storage medium, which stores a computer program. The computer program is suitable for being loaded by a processor and executing the above-mentioned layered frozen soil thawing and consolidation prediction method.

[0108] This embodiment also provides a device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the above-mentioned layered frozen soil thawing and consolidation prediction method is executed.

[0109] like Figure 2 As shown in the figure, the layered frozen soil model consists of two layers of soil with completely different properties. The top layer has a limited thickness, and the bottom layer is a semi-infinite space. v1 , k v2 Represent the permeability coefficient of the top soil and bottom soil, m v1 、m v2 Represent the volume compression coefficient of the top soil and bottom soil, C v1 , C v2 Respectively represent the consolidation coefficient of the top soil and the bottom soil, γ'1 and γ'2 represent the saturated density of the top soil and the bottom soil, and h1 is the thickness of the top soil. The model undergoes thawing consolidation under the action of transient pressure P0 and heat source.

[0110] like Figure 3 and Figure 4 As shown, the technical solution of this embodiment is compared with the MN model and Zhou model for thawing consolidation pore pressure distribution and consolidation ratio. Figure 3 and Figure 4 As known, the present invention can also be applied to the thawing consolidation model of homogeneous frozen soil.

[0111] like Figure 5 As shown, the heterogeneous model in the technical solution of this embodiment is compared with the homogeneous model for verification. The consolidation coefficients of each layer of the soil model are shown in Table 1, and the other parameters are P0 = 10 kN, h1 = 0.5 m, α = 3 × 10 -4 m / s 0.5 .

[0112] Table 1

[0113] Model Model A Model B Model C Model D <![CDATA[Coefficient of consolidation at the top layer, C v1 (×10 -8 m 2 / s)]]> 3 5 3 5 <![CDATA[Coefficient of consolidation of the underlying layer, C v2 (×10 -8 m 2 / s)]]> 3 5 5 3

[0114] Depend on Figure 5 As is known, ignoring the heterogeneity of layered frozen soil will affect the prediction of pore pressure distribution. This also reflects the advancement of the present invention.

[0115] like Figure 6 As shown (P0 = 10 kN, h1 = 0.5 m, C v2 =4×10 -8 m / s 2 ), in most cases, the consolidation ratio will decrease with the increase of the thawing coefficient, mainly because the larger the thawing coefficient means that more ice will thaw into water, and the drainage capacity of the soil itself is limited, so this situation occurs. The third step of the present invention is to adjust the heat source to make the consolidation ratio meet the engineering requirements. Therefore, when the consolidation ratio does not meet the engineering requirements, the thawing coefficient can be reduced to make the project meet the standards.

[0116] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for predicting thawing and consolidation of layered frozen soil, characterized in that: The steps include: Step 1: Obtaining relevant parameters of layered frozen soil; Step 2: Solve the pore pressure distribution model of thawing and consolidation of layered frozen soil in seasonally frozen areas to obtain the pore pressure distribution relationship in the thawing area; specifically, the steps include: The first step is to input the external influencing parameters required by the model; The second step is to construct boundary condition equations. Based on the different positions of the thaw line in the soil layer, the thaw line is defined as the first stage when it is at the top layer, and as the second stage when it is at the bottom layer. The bottom boundary conditions of the first stage and the second stage are obtained by solving the external influencing parameters and layered frozen soil related parameters in the first step. The top boundary conditions are defined based on the completely permeable interface in Terzaghi's theorem. The third step is to obtain the general solutions of the excess pore water pressure in the first and second stages of the model based on the control equation of soil consolidation and the Gaussian error function. Step 4: Based on the general solution of the first stage obtained in the third step and combined with the bottom boundary conditions and top boundary conditions of the first stage, the pore pressure distribution of the single-layer soil thawing consolidation in the first stage is obtained, and the initial conditions of the bottom layer in the second stage are obtained according to the bottom pore pressure at the end point of the first stage of pore pressure; Step 5: Based on the general solution of the pore pressure of the bottom soil in the second stage obtained in the third step and combined with the bottom boundary conditions of the second stage and the initial conditions of the second stage obtained in the fourth step, the distribution of the pore pressure of the bottom soil in the second stage is obtained; then, according to the Schiffman continuity condition, the top boundary condition and the general solution of the pore pressure of the top soil in the second stage, the distribution of the pore pressure of the top soil in the second stage is obtained; Step 3: Calculate the consolidation ratio of thawing and consolidation of layered frozen soil in seasonally frozen areas: Substitute the excess porosity pore pressure distribution obtained in the first and second stages in step 2 into the consolidation ratio solution formula respectively, and then obtain the consolidation ratio prediction structure of each stage, and compare the prediction results with the actual engineering requirements. If the engineering requirements are not met, return to the first step in step 2 to reset the external conditions until the engineering requirements are met.

2. The method for predicting thawing and consolidation of layered frozen soil according to claim 1, characterized in that: The layered frozen soil related parameters include the thickness, permeability coefficient, volume compression coefficient and saturated density of different soil layers.

3. The method for predicting thawing and consolidation of layered frozen soil according to claim 2, characterized in that: The layered frozen soil related parameters also include the movement of the thawing line S(t), and the consolidation coefficients of the top soil and the bottom soil.

4. The method for predicting thawing and consolidation of layered frozen soil according to claim 1, characterized in that: The external influencing parameters include the thawing coefficient of the thawing heat source and the initial external transient pressure.

5. The method for predicting thawing and consolidation of layered frozen soil according to claim 1, characterized in that: In step 3, the first stage consolidation ratio obtained is: The consolidation ratio of the second stage is obtained as:

6. A storage medium, characterized in that: The storage medium stores a computer program, and the computer program is suitable for being loaded by a processor and executing the layered frozen soil thawing and consolidation prediction method according to any one of claims 1 to 5.

7. A device, characterized in that: The device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the layered frozen soil thawing and consolidation prediction method according to any one of claims 1 to 5 is executed.

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