A Study On Seismic Bearing Capacity Of Sloping Ground Based On Unified Strength Theory

Ultimate bearing capacity of foundation as one of the three classical problems of the soil mechanics, has been deeply studied by lots of scholars. However, the present the formula of ultimate bearing capacity of foundation doesn't take the influence of intermediate principal stress into account. Experiments prove that the calculations of the present the formula of ultimate bearing capacity of foundation will lean to conservation because actually intermediate principal stress has considerable influence on submit and failure of materials, thus the strength potential of Geo-materials cannot be fully exploited. Furthermore, in the case of sloping ground condition which are happening with increasing frequency in the projects, as to how to ascertain ultimate bearing capacity, there is no specific computational methods in current norms. In addition, China is a nation of earthquake. Therefore, the issue of seismic bearing capacity and stability of foundation,has attracted more and more concern. Resting on the research achievements of other scholars and experts, the thesis aims to study seismic bearing capacity of soil sloping ground,rock sloping ground and reinforced-earth sloping ground on the basis of unified strength theory. The main research results are as follows:1. As to soil sloping ground. Based on the unified strength theory, by supposing composite curved failure plane and employing pseudo-static approach and the method of limit equilibrium analysis, a new formula of seismic bearing capacity of slope foundation in mountainous areas is obtained. The formula can be denoted by the combining form of three seismic bearing capacity coefficients as cohesion, surcharge and own weight ( N_cd, N_qd,N_γd).2. As to rock sloping ground. By applying the unified strength theory to Hoek-Brown failure criterion, a new form of Hoek-Brown failure criterion is obtained which is based on the unified strength theory. Then the form of shear strength of Hoek-Brown failure criterion based on the unified strength theory is deduced, and the method of fitting c,φis put forward. Finally, a new formula of seismic bearing capacity of rock slope foundation is deduced.3. As to reinforced-earth sloping ground. Based on the unified strength theory which takes the effect of intermediate principal stress into consideration, by supposing composite curved failure plane and employing pseudo-static approach the method of limit equilibrium analysis, and meanwhile considering the effect of reinforcement, a new formula of seismic bearing capacity of reinforced-earth of slope foundation in mountainous areas is obtained.4. By case study, analysis and comparison have been conducted on the unified answer and non unified answer of bearing capacity of slope foundation, seismic load's influence on bearing capacity, and the coefficient b's influence on the seismic bearing capacity coefficients. Thus come a serious of useful conclusions.