The Research on a Confined Modeling Method of the Effect of Deformable Ground Soil and Crawler Board

There is a great relationship between the passing capacity of vehicles on the ground deformation road and the properties of confined and shear of ground soil, so it is necessary to establish a model that can reflect the soil pressure of the deformation. Physical significance of classic soil pressure experience parameters model is indeterminate, it was generally obtained by a lot of specific soil test. In this paper a new analysis model was built though introducing the maximum stress value of the crawler board and soil surface on basis of a kind of existing analysis model. This model reveals the relations among the confined characteristics of soil, soil parameters and the geometry of confined crawler board. These soil parameters can be obtained through the conventional soil mechanics test without a large number of specific soil test. Through the contrast experiment and predictions results, this model can effectively predict the sinkage of ground soil under the load, and provide a theory basis for the prediction of vehicle mobility.


Introduction
The passing property of vehicles on the soft ground is closely related with soil pressure and shear resistance characteristics. In the study of vehicle ground mechanics, the empirical model is usually used to describe the confined characteristics of the soil. The most representative model is the model [1][2] made by M.G.Bekker. The model is based on the test of vehicle and soil parameters. The simplified equation is used to establish the relationship between the external load and the subsidence deformation of the soil, which provides a theoretical basis for vehicle performance testing. However, the physical meaning of the empirical parameters of the model is not clear. It is necessary to determine the parameters through a large number of expensive and time-consuming soil test tests, and the model is limited to a particular type of model. In recent years, many scholars have established a number of new empirical models [3][4], hoping that the model parameters are not dependent on specific soil tests, but the results show that these model parameters are still directly or indirectly related to the parameters of the Bekker model, and in essence the empirical parameters of the model need to be obtained through a large amount of specific pressure plate subsidence soil tests. Kacigin, Ageikind [5] establish an analytical model, including the external load of soil, the geometric size of the plate, the subsidence of soil and the mechanical properties of soil, which reflects the relationship between the amount of soil subsidence, the load of the soil and the stress in the soil, in which the model parameters can be obtained through the conventional soil mechanics test without a large number of specific soil test. It is only the model that considers the external load applied by the plate / wheel as the uniformly distributed load, which results in inaccurate prediction of the model. On the basis of the analysis model, considering the influence of the soil stress on the maximum stress on the contact surface of the Caterpillar board and the soil, a new analysis model is established to establish the relation between the soil subsidence and the size of the load, the parameters of soil characteristics and the size of the plate, and the test method of the model parameters is given, and the test is tested. It is reasonable to predict the subsidence of soil by the model, which provides a theoretical basis for studying the subsidence deformation of deformable ground soil under the action of vehicle.

The influence of contact stress between track plate and soil on normal stress
Ageikind et al [6] believes that the normal stress at the z depth of soil is related to the geometric characteristics of the plate and the uniform load of the contact surface, as shown in formula (1) and The recent research shows that the stress in the soil is related to the maximum stress of the contact surface, not the average stress of the contact surface. Therefore, the maximum stress of the contact surface is introduced in this paper to amend the analysis model proposed by Ageikind and to establish a new analytical model, such as formula (3). According to the classical soil mechanics [7], the maximum stress on the contact surface between the plate and the soil is 3 times that of the average stress on the contact surface, and the relationship between them is shown by formula (4).  (4) [ is a dimensionless constant, independent of the state of the soil, and only related to the width

Soil pressure characteristic model
According to the dynamic soil theory, the force of the crawler and the soil is shown in Figure 2, and the normal pressure on the vertical crawler and the passive earth pressure p V the depth of Z below the a point can be expressed by the formula (5) [8].

Test verification
The soil parameters are

Conclusion
Based on the dynamic soil pressure and limit equilibrium theory, this paper analyzes the interaction relationship between the crawler plate and the ground soil, and establishes an analysis model of the soil pressure characteristics. The model establishes the relationship between the geometric parameters of the crawler plate, the soil subsidence, the external load and the vehicle driving parameters, and These soil parameters can be obtained through the conventional soil mechanics test without a large number of complex and specific soil test. It's discovered that the prediction results of the model are basically the same as those of the test results by comparison with test results, which provides a theoretical basis for predicting the mobility of vehicles.