CN1609351A - Establishment method of generalized Bingheim soft soil rheological deformation simulation body - Google Patents

Abstract

The generalized Bingham soft earth rheologic deformation model is for building structure deformation controlling design and relevant research. The model establishing process includes the following steps: a. inputting embankment design parameters; b. inputting composite foundation processing parameters; c. automatic grid division; e. inputting model parameters; f. embankment load increment; g. reclamation time increment; h. coupling plastomer with generalized Bingham body based on Bitot consolidation formula; i. determining unit stiffness matrix and establishing code and characteristic of each grid unit body; j. constituting overall rigidity matrix; k. finite element solving Bitot consolidation formula to find the solutions in the points within the researched space; l. judging whether to meet the boundary condition, and if no, returning to i.; m. calculating the node force, displacement and hole pressure and returning results to f. and g.; and n. outputting results to end.

Description

Establishment method of generalized Bingheim soft soil rheological deformation simulation body

Technical field

The invention is a method for controlling deformation design of building structure and related research. In particular, a method for establishing a generalized Bingheim soft soil rheological deformation simulation body directly applied in the field of civil engineering.

Background technique

In recent years, my country has been carrying out large-scale infrastructure construction, such as the construction of key projects such as highways and railways. During the construction of highways and railways, it is inevitable to pass through soft soil areas, and build highways and railways in soft soil areas. There are often many engineering problems, such as excessive subsidence and deformation of the subgrade, which affect normal traffic: vehicle jumping occurs at the bridgehead and box culvert connection parts, and the settlement of culverts affects the smooth flow of the water system, and there are hidden dangers of flood control. This is mainly due to insufficient understanding of the deformation characteristics of soft soil, or the inability to use an accurate deformation model to describe the rheological deformation characteristics of soft soil. Although many achievements have been made in this area, the understanding of the rheological properties of soft soils, such as the Maxwell model can only describe the stress relaxation phenomenon of soils, and the Kelvin model can only describe the elastic after-effect properties of soils. The -Huang model and Bingheim can only describe the ultimate strength of the soil, and these phenomena cannot accurately describe the process and phenomenon of subgrade deformation and failure. Because the deformation and failure of the subgrade is a process from gradual change to sudden change at the beginning, the gradual deformation at the beginning can be approximated as elastic-plastic, and the final sudden change is the ultimate failure phenomenon.

Contents of Invention

Technical problem: The purpose of this invention is to propose a method for establishing a generalized Binheim soft soil rheological deformation simulation body, which can accurately describe the rheological deformation characteristics of soft soil, so as to realize the controlled deformation design of highways and railways.

Technical solution: Many expressways and railways in my country are in operation (such as the Lianyungang section of the Longhai Railway being repaired every year, and the cumulative subsidence of the roadbed is close to 2 meters), and some of them are deformed and damaged during the construction process ( Such as the Lianyungang section of the second phase of Lianxu Expressway), which affects the normal operation of the project and causes a lot of economic losses. In order to accurately describe the characteristic phenomenon of subgrade settlement and deformation, and provide a reliable theoretical basis for engineering design, the inventor conducted on-site investigations, indoor tests and calculations to summarize and analyze engineering characteristic phenomena. A generalized Bingheim rheological model of soft soil can accurately describe the characteristic phenomena of rheological deformation of soft soil.

The model is composed of two parts, one part is elastoplastic body, which describes the elastoplastic deformation of embankment with gradual deformation; the other part is generalized Bingheim body, which describes the rheological deformation and failure characteristics of embankment. The two unit elements are linearly combined through the Biot consolidation equation, and the parameters of the relevant unit bodies are determined by experiments, and the relevant numerical algorithms are established to accurately describe the characteristics of the embankment settlement deformation.

For the simulation calculation of the model, firstly, the research object is meshed for the foundation and embankment under study and related control parameters, including the height of the embankment, the width of the embankment up and down, the average bulk density parameter and the layered thickness parameter of the soil layer of the foundation, and then The model parameters are obtained through the conventional triaxial test and the K ₀ consolidation triaxial rheological test. These parameters mainly describe the test parameters of the elastic-plastic deformation and rheological deformation characteristics of the soil; set the load increment and Time increment, the Biot consolidation equation couples the elastoplastic body with the generalized Bingheim model, determines the stiffness matrix of the unit body and the overall stiffness matrix, and uses finite elements to solve numerically, and numerically calculates the stress, displacement and The pore water pressure value is used to finally calculate the settlement deformation of the subgrade.

The method to build the model is:

a. Input the embankment design parameters, namely embankment crest, bottom width, embankment height and average bulk density;

b. Input composite foundation treatment parameters, namely treatment depth, replacement rate and soil layer parameters;

c. Automatic grid division;

e. Input model parameters, that is, input the elastic-plastic unit parameters of the conventional triaxial test, and the rheological unit parameters of the triaxial rheological test of the K ₀ consolidation method; the K ₀ consolidation method is a set geotechnical test method, which requires The ratio of the lateral pressure to the vertical pressure that the tested soil sample bears is equal to the constant _K0 for deformation testing:

f. Embankment load increment, that is, the filling height of a certain layer of embankment, is equivalent to the action force, that is, the magnitude increment of the load;

g. Filling time increment, that is, the filling time of a certain layer of embankment, which is equivalent to the interval increment of continuous filling time;

h. Establish the Biot consolidation equation to describe the deformation of the soil, and couple the plastic body with the generalized Binheim body, that is, establish the connection between the elastoplastic body and the Binheim limit failure body through the Biot consolidation equation:

i. Determine the unit stiffness matrix, and establish a code for each grid unit body, such as the magnitude of the force and the displacement deformation generated:

j. Constitute the overall stiffness matrix, that is, describe the force and displacement deformation of the entire research object according to its encoding and sorting for all grid units:

k, finite element solution to the solution of Biot's consolidation equation at each point in the research space (the position of each point in the space is determined by the automatic grid subdivision of step c), which includes the force and deformation on the grid unit and grid nodes :

l. Whether the boundary conditions are satisfied, if not, return to step I to determine the element stiffness matrix; if the boundary conditions are satisfied, perform the following step m,

m. Calculate the nodal force, displacement, and pore pressure, and return the calculation results to step f and step g for circulation;

n. Output the calculation result and end.

Beneficial effects: Based on this generalized Bingheim rheological model of soft soil, the deformation characteristics of soft soil roadbed can be accurately described, and a theoretical basis can be provided for determining a reasonable soft soil foundation reinforcement treatment method, so as to realize control deformation design and ensure the safety of highways and railways At the same time, it reduces the economic loss caused by the out-of-control settlement and deformation, and saves a lot of maintenance costs, which has obvious economic benefits.

Description of drawings

Figure 1 is a schematic diagram of the generalized Bingheim soft soil rheological deformation simulation method.

Figure 2 is a schematic diagram of a calculation example.

Fig. 3 is a schematic diagram of the establishment method of the generalized Bingheim soft soil rheological deformation simulation body.

Detailed ways

The establishment method of generalized Binheim soft soil rheological deformation simulation of the present invention is an example illustration at the expressway K20+395 place of four lanes in the Lianyungang section of Lianxu Expressway, embankment height 5m, embankment top width 28m, bottom width 43m, The average bulk density of the embankment is generally 20kN/m ³ ; the soft soil foundation is relatively simple, the thickness of the soft soil is 12m, and the soil layer under the soft soil layer is also relatively single and uniform. 0.157.

a. Input the design parameters of the embankment, namely, embankment crest, bottom width, embankment height, and average bulk density; the specific values are 28, 43, 5, and 20 respectively;

b. Input the composite foundation treatment parameters, namely treatment depth, replacement rate and soil layer parameters; the specific values are 12.5, 0.157 and 4 respectively;

c. Automatic grid division;

e. Input model parameters, that is, input the elastic-plastic unit parameters of the conventional triaxial test, and the rheological unit parameters of the triaxial rheological test of the K ₀ consolidation method; the K ₀ consolidation method is a set geotechnical test method, which requires The ratio of the lateral pressure to the vertical pressure that the tested soil sample bears is equal to the constant K ₀ for deformation testing; take K ₀ =0.65 (obtained by the test), and the rheological viscosity parameter η=3.5*10 ^-5 (min ^-1 ), and some other parameters are experimental statistical parameters;

f. Embankment load increment, that is, the filling height of a certain layer of embankment, is equivalent to the action force, that is, the increment of load; embankment height is 5m, which is approximately divided into four times of filling, and the load increment is 25kPa;

g. Filling time increment, that is, the filling time of a certain layer of embankment, which is equivalent to the interval increment of continuous filling time; the construction time of expressway is generally 3 to 4 years, and the calculation time interval can usually be taken as 20 ~ 40 days, the calculation time interval is 20 days;

h. The Biot consolidation equation couples the plastic body and the generalized Bingheim body, that is, the elastic-plastic body and the Bingheim limit failure body are connected through the Biot consolidation equation;

i. Determine the unit stiffness matrix, and establish codes and characteristics for each grid unit body, such as the magnitude of the force and the displacement deformation generated;

j. Constitute the overall stiffness matrix, that is, sort all grid units according to their codes and characteristics, and describe the force and displacement deformation of the entire research object;

k. Solve the solution of Biot's consolidation equation on each grid unit and grid node by finite element method, including the force and deformation on the grid unit and grid node;

l. Whether the boundary conditions are satisfied, if not, return to step I to determine the element stiffness matrix; if the boundary conditions are satisfied, perform the following step m,

m. Calculate the nodal force, displacement, and pore pressure, and return the calculation results to step f and step g for circulation;

n. Output the calculation result and end. The calculation results are shown in Figure 2.

Aiming at the consolidation deformation and rheological characteristics of marine soft soil in Lianyungang, Jiangsu, a generalized Bingheim soft soil rheological body is established, and the elastic-plastic deformation body of the soil is organically combined with the generalized Bingheim limit failure body. Compile relevant calculation software for settlement calculation, the settlement calculated by the elasto-viscoplastic model considering rheology is relatively close to the measured settlement (the error is less than 10%), and the settlement accuracy calculated by the elastoplastic deformation body is increased by more than 40%. It has been successfully applied to the design of the second phase of the Lianyungang section of the Lianxu Expressway, and at the same time, this research achievement has been extended and applied to the design of the Fenguan Expressway and the Lianyan Expressway.

Claims (1)

1, a kind of method for building up of broad sense Bingham soft soil rheological deformation simulative is characterized in that method for building up is as follows:

A, input embankment design parameters, i.e. levee crown, bottom width, dike height, average unit weight;

B, input composite foundation processing parameter are promptly handled the degree of depth, replacement ratio, soil layer parameter;

C, grid automatic division;

E, input model parameter are promptly imported the elastoplasticity cell parameters of ordinary triaxial test, K ₀The rheological unit parameter of concretion method triaxial rheology test;

F, embankment load increment, i.e. certain one deck embankment filled height, being equivalent to active force is the size increment of load;

G, fill incremental time, be certain one deck embankment and fill the time, be equivalent to the space increment of the time of filling continuously;

H, Biot consolidation equation are coupled plastic body and generalized Bingham body, are about to the elasticoplastic body and Bingham limit destruction body and get in touch by Biot consolidation equation foundation;

I, determining unit stability matrix are set up coding and feature to each grid cell body, as stressed size, and the displacement deformation of generation;

J, formation global stiffness matrix are about to all grid cell bodies according to its coding and ordering, describe the stressed and displacement deformation of whole research object;

K, finite element solving Biot consolidation equation separating on the each point of research space, this comprises stressed size and distortion size on grid cell and the grid node;

L, fringe conditions satisfy not, if do not satisfy fringe conditions, then return step I, the determining unit stability matrix; If satisfy fringe conditions, then carry out following step m,

Press in m, calculating joint forces, displacement, hole, simultaneously result of calculation is back to step f and step g and circulates:

N, output result of calculation finish.