Numerical Simulations And Experimental Studies Of The Effects Of Mudcake On The Vertical Bearing Behavior Of Bored Piles

With the rapid development of high-rise buildings, bored pile foundation has become one of the main foundation forms, but due to imperfection of construction technologies and engineering levels, it is common that some pile foundations contain defective piles. At present, the academic researches about defective piles mainly focus on detection and location.However, few researches have been made on the bearing mechanism of defective piles. Based on the fact, the thesis presents a study on the vertical bearing mechanism and working behavior of piles with mudcake.With establishing finite axisymmetric element models of pile-mud-soil, a study has been made on the effects of thickness, modulus of elasticity, friction angle, cohesion of mud and friction coefficient on vertical ultimate bearing capacity of single pile with the help of the finite element analysis software ABAQUS. Also, the load-bearing mechanism about mudcake piles has been obtained by studying and analyzing load settlement graphs, shaft resistance curves and axial force curves. The results of the study show the existence of mud will affect vertical ultimate bearing capacity of single pile from two aspects: normal stress and tangential stress. The increasing of mud thickness and decreasing of the elastic modulus lead to normal stress reducing and squeezing weakening; the decreasing of angle of friction, cohesion of mud and the coefficient of friction made limit friction stress smaller and pile slipping ahead of time, pile tip displacement much larger. In a word, as weak intercalated layer between pile and soil, mud has greatly reduced shaft resistance and resulted in lower load-capacity. The thesis also compares load settlement graphs from the laboratory model experiment and the numerical simulation and the results show that the regularities from the two are consistent.The research of this thesis, to some extent, reveals the bearing behavior and working mechanisms of mudcake piles and it may present positive guidance to analyses and assessments of defective piles behavior with mudcake.