A simulation prediction method for creep settlement of deep soft soil foundation

Abstract

The invention discloses a method for simulating and predicting creep settlement of a thick soft soil foundation. First, the consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth index of the soft soil foundation to be detected are obtained; then, the parameters of a generalized Kelvin model are solved according to the obtained consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth index; then, the strain of the soil body changing with time is obtained according to the obtained parameters of the generalized Kelvin model; finally, the creep settlement of the thick soft soil foundation is predicted according to the obtained soil body strain, combined with the thickness of the soft soil foundation and the required calculation time.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation settlement simulation analysis, and in particular relates to a method for simulating and predicting creep settlement of a deep soft soil foundation. Background Art

[0002] There are two major characteristics of soft soil foundation deformation: one is high compressibility and large deformation, and the other is poor permeability and long deformation duration, which has a great impact on the deformation characteristics of the foundation. The thick soft soil foundation has a large total settlement, and its post-construction creep settlement is often also large, making this problem more complicated. At present, the calculation of the creep settlement of thick soft soil foundation generally adopts a method combining indoor geotechnical tests and numerical simulations, that is, generally using uniaxial creep tests or triaxial creep tests to obtain the creep constitutive model parameters, and then bringing the creep parameters into the numerical analysis software to analyze the creep parameters. However, the above method has the following disadvantages: ① The creep test cycle is long and the data is numerous. Taking the uniaxial creep test as an example, the consolidation loads are 25kPa, 50kPa, 100kPa, 200kPa, 400kPa, 800kPa and 1600kPa, and the creep stability standard is 0.005mm / d, then the test cycle is 2 to 3 months; ② The model parameters are greatly affected by the load. When calculating, the average value of the creep parameters under each level of consolidation load is generally taken, resulting in inaccurate calculation of creep settlement; ③ There are many creep parameters, which is not conducive to engineering applications. For example, the five-element generalized Kelvin model has a total of five parameters. When the thickness of the deep soft soil foundation is 60m, in order to improve the creep calculation accuracy, a soil layer is divided every 1m, then there are 2100 creep parameters under 7 levels of consolidation load. Summary of the invention

[0003] In order to overcome the deficiencies of the prior art, the present invention provides a method for simulating and predicting creep settlement of a deep soft soil foundation.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for simulating and predicting creep settlement of a thick soft soil foundation comprises the following steps:

[0006] Step 1: Obtain the consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth index of the soft soil foundation to be tested;

[0007] Step 2: Substitute the consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth obtained in step 1 into equations (1) to (5) to solve the parameters of the generalized Kelvin model: E H、 E K1、 E K2、 or K1和 orK2；

[0008] (1) ;

[0009] (2) ;

[0010] (3);

[0011] (4);

[0012] (5);

[0013] In the formula, E H is the elastic modulus of the Hooke body; or K1、 or K2 is the viscosity coefficient of the Kelvin body; E K1、 E K2 is the elastic modulus of the Kelvin body; is the consolidation load; is the void ratio; is the liquid limit porosity ratio; is the atmospheric pressure; is the bulk density; For burial depth;

[0014] Step 3: The parameters of the generalized Kelvin model obtained in step 2 E H、 E K1、 E K2、 or K1和 or K2 Substituting into equation (6), we can obtain the strain of soil changing with time;

[0015] (6);

[0016] In the formula, is the soil strain, For time;

[0017] Step 4: Based on the soil strain obtained in step 3, combined with the thickness of the soft soil foundation and the required calculation time, the creep settlement of the deep soft soil foundation is predicted.

[0018] In the above technical solution, in step 1, the bulk density , porosity ratio Liquid limit porosity It can also be obtained through indoor geotechnical tests.

[0019] In the above technical solution, in step 4, the soft soil foundation is divided into n soil layers along the thickness direction, and the thickness of each soil layer is , predicted experience Creep settlement of soft soil foundation after time;

[0020] First, the creep deformation of each soil layer is calculated as:

[0021] (7);

[0022] In the formula, For the Elastic modulus of Hooke body of generalized Kelvin model of soil layer; , For the Kelvin volume viscosity coefficient of the generalized Kelvin model of soil layer; , For the Kelvin body elastic modulus of the generalized Kelvin model of soil layer; For the Creep deformation of soil layer;

[0023] but At this moment, the creep settlement of the entire soft soil foundation is:

[0024] (8);

[0025] In the formula, is the creep settlement of the entire soft soil foundation.

[0026] The advantages and beneficial effects of the present invention are:

[0027] The method of the present invention can directly obtain the parameters required for soft soil foundation creep prediction through survey data or conventional indoor geotechnical tests (density test, liquid limit test, etc.), greatly reducing the test cycle; the present invention establishes a creep equation that comprehensively considers consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth index, and simplifies the parameters of creep calculation. For example, when the thickness of the deep soft foundation is still 60m, a soil layer is divided every 1m, and the number of parameters considered is 300, which is only 1 / 7 of the original number of parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 yes E H Normalized fitting curve.

[0029] Figure 2 yesE K1 - E H Normalized fitting curve.

[0030] Figure 3 yes E K1 - E K2 Normalized fitting curve.

[0031] Figure 4 yes or K1 Normalized fitting curve.

[0032] Figure 5 yes or K2 Normalized fitting curve.

[0033] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with specific embodiments.

[0035] A method for simulating and predicting creep settlement of a thick soft soil foundation comprises the following steps:

[0036] Step 1: Obtain the soil consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth of the soft soil foundation to be tested.

[0037] Obtain soil consolidation load based on soft soil foundation survey data and project construction plan , bulk density , porosity ratio , Liquid limit porosity And the depth ; Among them, bulk density , porosity ratio Liquid limit porosity It can also be obtained through indoor geotechnical tests;

[0038] Step 2: Substitute the consolidation load, bulk density, void ratio, liquid limit void ratio, and burial depth obtained in step 1 into equations (1) to (5) to solve the parameters of the generalized Kelvin model: E H、 E K1、 E K2、 or K1和 orK2。 The specific steps are as follows: Substitute the consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth into formula (1) to obtain the parameters ,like Figure 1 As shown; the consolidation load, bulk density, burial depth and E H Substituting into formula (2) we get the parameters E K1， like Figure 2 As shown; the parameters E H and E K1 Substituting into equation (3) we can solve the parameter E K2 ,like Figure 3 As shown; the consolidation load, bulk density, burial depth and parameters E H Substituting into equation (4) and equation (5) we get the parameters or K1和 or K2， like Figure 4 and Figure 5 As shown;

[0039] (1) ;

[0040] (2) ;

[0041] (3);

[0042] (4);

[0043] (5);

[0044] In the formula, E H is the elastic modulus of the Hooke body, kPa; or K1和 or K2 is the viscosity coefficient of the Kelvin body, kPa·min; E K1、 E K2 is the elastic modulus of the Kelvin body, kPa; is the consolidation load, kPa; is the void ratio; is the liquid limit porosity ratio; is the atmospheric pressure, kPa; is the soil bulk density, kN / m 3 ; is the burial depth, m;

[0045] Step 3: The parameters of the generalized Kelvin model obtained in step 2 E H、 E K1、 E K2、 or K1和 or K2 Substituting into equation (6), we can obtain the strain of soil changing with time;

[0046] (6);

[0047] In the formula, is the soil strain, For time;

[0048] Step 4: Based on the soil strain obtained in step 3, combined with the thickness of the soft soil foundation and the required calculation time, the creep settlement of the deep soft soil foundation is predicted.

[0049] According to the geological survey data, the deep soft soil foundation is divided into n soil layers along the thickness direction. The thickness of each soil layer is , predicted experience Creep settlement of thick soft soil foundation after time.

[0050] According to the data obtained from step 1 to step 3, firstly, the creep deformation of each soil layer can be calculated as:

[0051] (7);

[0052] In the formula, For the Elastic modulus of Hooke body of generalized Kelvin model of soil layer; , For the Kelvin volume viscosity coefficient of the generalized Kelvin model of soil layer; , For the Kelvin body elastic modulus of the generalized Kelvin model of soil layer; For the Creep deformation of soil layer;

[0053] but At this moment, the creep settlement of the entire soft soil foundation is:

[0054] (8);

[0055] In the formula, is the creep settlement of the entire soft soil foundation.

[0056] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. A method for simulating and predicting creep settlement of thick soft soil foundation, characterized in that: The following steps are involved: Step 1: Obtain the consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth index of the soft soil foundation to be tested; Step 2: Substitute the consolidation load, bulk density, void ratio, liquid limit void ratio and burial depth obtained in step 1 into equations (1) to (5) to solve the parameters of the generalized Kelvin model: E H、 E K1、 E K2、 η K1和 η K2； （1） ； （2） ； （3）； （4）； （5）； In the formula, E H is the elastic modulus of the Hooke body; η K1、 η K2 is the viscosity coefficient of the Kelvin body; E K1、 E K2 is the elastic modulus of the Kelvin body; is the consolidation load; is the void ratio; is the liquid limit porosity ratio; is the atmospheric pressure; is the bulk density; For burial depth; Step 3: The parameters of the generalized Kelvin model obtained in step 2 E H、 E K1、 E K2、 η K1和 η K2 Substituting into equation (6), we can obtain the strain of soil changing with time; （6）； In the formula, is the soil strain, For time; Step 4: Based on the soil strain obtained in step 3, combined with the thickness of the soft soil foundation and the required calculation time, the creep settlement of the deep soft soil foundation is predicted.

2. The method for simulating and predicting creep settlement of deep soft soil foundation according to claim 1, characterized in that: In step 1, bulk density , porosity ratio Liquid limit porosity It can also be obtained through indoor geotechnical tests.

3. The method for simulating and predicting creep settlement of deep soft soil foundation according to claim 1, characterized in that: In step 4, the soft soil foundation is divided into n soil layers along the thickness direction, and the thickness of each soil layer is , predicted experience Creep settlement of soft soil foundation after time; First, the creep deformation of each soil layer is calculated as: （7）； In the formula, For the Elastic modulus of Hooke body of generalized Kelvin model of soil layer; , For the Kelvin volume viscosity coefficient of the generalized Kelvin model of soil layer; , For the Kelvin body elastic modulus of the generalized Kelvin model of soil layer; For the Creep deformation of soil layer; but At this moment, the creep settlement of the entire soft soil foundation is: （8）； In the formula, is the creep settlement of the entire soft soil foundation.

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