Study On Calculation Method Of Bearing Capacity Of Red-soil Mudstone Pile Foundation Considering Pile-rock Interaction

The pile-soil interaction is the core issue of the pile foundation's bearing capacity. However, there are rarely researches on the shear properties of mudstone and structure interfaces at present, and the existing interaction mechanism of coarse-grained soils, sand and piles are not suitable for the red mudstone stratum. The mud cake, which is buried between the pile body and the surrounding rock is an important factor influencing the pile-rock interaction. In brief, the mud cake can be treated as a weak interlayer which possesses high compressibility and low shear strength, leading to the decrease of lateral negative friction resistance of pile. The paper aims to solve the practical engineering problems combining with the pile-rock interaction mechanism. Firstly, the laboratory soil tests are performed to obtain the physical and mechanical parameters of red mudstone cake. Secondly, the shear properties of pile-rock interface and its constitutive relationship are studied via direct shear tests of the interface. Employing the finite-difference software FLAC3D, models of both the normal pile and mud-cake pile can be established. Finally, the the influence of mud cake on bearing capacity of red mudstone pile foundation is researched and the computational method of bearing capacity is modified based on the numerical methods. In detail, the paper mainly includes the following parts:(1)Collecting red mudstone samples and making concrete block. Through the laboratory large pile-rock interface shear test, the shear failure characteristics of pile-rock interface are obtained and the constitutive model of red mudstone pile-rock interface is established. Specifically, the detailed constitutive equation is deduced(2)First of all, the formation mechanism of mud cake is analyzed. The physical and mechanical parameters are obtained through field sampling and laboratory soil tests. Theses parameters are necessary for the later numerical model. Meanwhile, some literatures are collected to count the physical and mechanical parameters of mud cake from other stratum and the difference between the mud-cake soil and undisturbed soil is also studied.(3)Using finite-difference software FLAC3D, the red mudstone model for single pile static load test is established. Firstly, Compared to normal pile foundation, the bearing characteristics of red mudstone pile foundation with mud cake is analyzed. Then, the parameter sensitivity of mud-cake pile foundation static load test is conducted which mainly included the thickness, elastic modulus, cohesion, and the internal friction of mudcake(4)Through analyzing the numerical simulation results, the paper puts forward the correction coefficient of mud-cake thickness pile foundation, and the calculation formula of bearing capacity are modifiedNowadays, with the large-scale development of pile foundation engineering, the mud-cake defected pile foundation's bearing characters has got more and more attention. The research results of this paper aims at providing references to the determination of bearing characters of the mud-cake pile in red mudstone stratum.