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SOIL MECHANICS - CHAPTER 31

Biến dạng của ĐẤT lớp Một vấn đề quan trọng của thực hành cơ học đất là dự đoán của các khu định cư của một cấu trúc được xây dựng trên đất. Đối với một vật liệu đồng nhất và đẳng hướng đàn hồi tuyến tính biến dạng có thể được tính bằng cách sử dụng lý thuyết đàn hồi. Đó là một lý thuyết hoàn toàn phù hợp, dẫn đến biểu hiện cho những căng thẳng và chuyển vị. | Chapter 31 DEFORMATION OF LAYERED SOIL An important problem of soil mechanics practice is the prediction of the settlements of a structure built on the soil. For a homogeneous isotropic linear elastic material the deformations could be calculated using the theory of elasticity. That is a completely consistent theory leading to expressions for the stresses and the displacements. However solutions are available only for a half I.I space and a half plane not for a layered material at least not in closed form . Moreover soils exhibit . non-linear.properties such as a stiffness increasing with the actual stress often have anisotropic . properties .and in many cases the soil consists of layers of different properties. For such materials the J- J-.z J- J. . . . description of the material properties is already a complex problem let alone the analysis of stresses and deformations. For these reasons an approximation is often used based on a semi-elastic analysis. In this approx-Figure 31 1 Load on layered soil imation it is first postulated that the vertical stresses in the soil whatever it true properties are can be approximated by the stresses that can be calculated from linear elastic theory. On the basis of these stresses the deformations are then determined using the best available description of the relation between stress and strain which may be non-linear. If the soil is layered the deformations of each layer are calculated using its own properties and then the surface displacements are determined by a summation of the deformations of all layers. In this way the different properties of the layers can be taken into account including a possible increase of the stiffness with depth. The procedure is not completely consistent because in a soil consisting of layers of different stiffness the stress distribution will not be the same as in a homogeneous linear elastic material. A partial justification may be that the stresses following from an elastic computation at least