Research On The Computational Method Of Earth Pressure For The Excavations In Fissured Clay In Chengdu Area

Some pit accidents of the clay area often appear in Chengdu. Through a research and analysis, it shows that the deformation and destruction of pits is related to water and cracks in the clay. Due to the estimation of earth pressure, which is an important part of designing excavation, it is very important for the research on earth pressure of fissured clay in Chengdu.This paper is involved with the research on the effect of moisture, fracture spacing and angle on shear strength of Chengdu clay through lot of laboratory experiments. Besides, the paper also includes the analysis on the impact of moisture on the pit earth pressure through the finite element software. At last, with the help of discrete element software the paper makes an a analysis on the effect of fracture spacing, fracture angle, more sets of cracks, cohesion and internal friction angle of cracks on the pit earth pressure. The results are concluded as follows:(1) The soil strength is influenced by the changes in the moisture content obviously. And, the strength of undisturbed soil is greater than that of saturated soil. Because of the increasing of moisture content and the decreasing of the soil strength, its pit earth pressure will increase with the increasing of horizontal displacement of retaining pile.(2) Fissure angle has a significant impact on the pit earth pressure. When the angle of cracks is less than the internal friction of cracks, the pit earth pressure is almost not influenced by fissures. Moreover, when the angle of cracks is more than its internal friction angle, pit earth pressure increases to the maximum but then decreases with the increasing of angle.(3) The results for fracture spacing show that the smaller the fracture spacing is, the bigger the pit earth pressure is. But the pit earth pressure will not increase indefinitely. When the growth of cracks is up to a certain extent, earth pressure will stabilize gradually.(4) The research on multiple fracture sets shows that the more fracture sets are, the more complicated the engagement and dislocation of fractures are and the larger their mutual influence is. The strength of the other set of cracks is weakened by one set; therefore, earth pressure of multiple fracture sets is stronger than one set under the same conditions.(5) The impact of fracture Strength on pit earth pressure is not ignorable. The increase of internal friction angle and cohesion of fracture will lead to the decrease of the earth pressure. When the strength of fracture is very close to that of earth, the pit earth pressure will be reduced.