Study On The Ultimate Bearing Capacity Of Strip Foundations On Slopes Or Adjacent To Slopes And Its Influencing Factors

In the field of engineering construction, foundations are sometimes placed on slopes or adjacent to slopes. In the present research work, there is still not a clear exposition about the failure mode of foundations on slopes or adjacent to slopes, there also has no accurate method to calculate the ultimate bearing capacity of these foundations. If we can accurately calculate the ultimate bearing capacity of these foundations, which will provide theoretical basis for designing of it, the design of foundation engineering will be more reliable and reasonable, and the construction cost of foundations will be effectively reduced. In the paper, the failure mode, the ultimate bearing capacity and its influencing factors of strip foundations on slopes or adjacent to slopes are discussed deeply and systematacially in the way of theoretical methods, such as limit equilibrium method, limit analysis method, etc. combined with centrifugal model test. Results are as follows:1. The computation model has been developed for obtaining the ultimate bearing capacity of foundations on slopes or adjacent to slopes, the computation formula to obtain the ultimate bearing capacity is also deduced using limit equilibrium and limit analysis approaches. Results indicate that the computation formula above has a high accuracy. Moreover, the influence of several factors on the ultimate bearing capacity is analyzed by programming. Compared with the existing achievements, the analysis on influencing factors for three bearing capacity factors are more comprehensive and in-depth. As the concept of "Equivalent free surface" and "virtual slide surface" is introduce, and considering the static balancing action of soil after the slope to elastic wedge ADE under the foundation, double sides slip failure model for foundations on small slope is developed. As a result, the computational accuracy for the ultimate bearing capacity of foundations on small slope is improved.2. Based on slip line theories, slip failure model for foundations on slopes or adjacent to slopes has been developed. According to the plastic boundary conditions of soil before and after the slope for foundations on slopes or adjacent to slopes, introducing the concept of "influence coefficient of distance from the edge of slope ", the analytical formula to calculate the ultimate bearing capacity of foundations on slopes or adjacent to slopes without considering the weight of the soil is deduced using slip line theories, which give a convenient approach to estimate the ultimate bearing capacity of foundations on slopes or adjacent to slopes quickly. For foundations considering the weight of the soil, the specific method is also proposed, namely the ultimate bearing capacity of it can be obtained by the way of making stress fields using finite difference method according to known boundary conditions. In the paper, the way how to get the slip line field and stress field in the whole foundation soil by finite difference method based on slip line theories is introduced. The results are also verified by way of examples. The method provides an effective way to obtain accurate displacement field, stress field for foundations on slopes or adjacent to slopes.3. The deformation and failure mechanism for foundations on slopes or adjacent to slopes is studied by numerical simulation, as a result, the displacement field and stress field under different conditions of these foundations soil are obtained. Bases on the results from the numerical simulation, the influence of factors such as soil cohesion, internal friction angle, angle of slope, distance from the edge of slope, depth of foundation below ground surface, the height of slope, roughness of foundation base on the ultimate bearing capacity of foundations on slopes or adjacent to slopes is analyzed. For pure clay, the concept of "transition point" and "critical intensity" are proposed, the quantitative corresponding relationship between soil strength and failure modes for foundations on slopes or adjacent to slopes is established, and the typical contour charts of the ultimate bearing capacity for these foundations are presented based on statistical analysis of simulation data, which will provide a reference for quickly and accurately determining the ultimate bearing capacity of foundations and studying slope stability in the actual slope project.4. By centrifugal model tests, the deformation mechanism and failure mode of foundations adjacent to slopes under strip loads are further studied; research contents also include the influence of factors such as location of load, roughness of foundation and width of strip foundation on the ultimate bearing capacity of foundations. Moreover, test results and theoretical calculation results are compared to verify the feasibility of the theoretical analysis method.