The Interaction Of Loess Area Caisson Wall And Soil

The research focuses on the sinking process of the shaft foundation of YF’70and YF’71in Xi’an. The author examines the engineering and hydrographicgeology there through a close reconnaissance survey, and monitors the wholesinking process of the shaft. In order to learn the changing law of shear behaviorof soil-concrete structure surface，an experimental study on soil-concrete structurecontact surface is carried out by considering various soil water contents andvarious soil density.64shearing tests， which are related to soil-soil andsoil-concrete contact surface，are conducted by using the large-scale direct shearapparatus. According to experimental data analysis and the shearing stress-straincurve, basic mechanical principles of soil-concrete structure interface are obtained.In conclusion, shear strength specimen decreases with large water content of soiland increases with large soil density. Experimental data also shows thatmechanical properties of soil-concrete structure contact surface, such as shearstrength, cohesion force and friction angle，closely depend on soil water contentand soil density. Through the systematic analysis of the properties, the distributionof wall side friction and end bearing, daring penetrating into different soil strata isobtained. Specifically speaking, the earth pressure on the foot blade of an opencaisson is the passive earth pressure, while the earth pressure on the wall of anopen caisson is the active earth pressure or the earth pressure at rest. Based on thetheory of failure of subsoil, the compressed core sinking with the open caisson isregarded as part of the foundation, then the displacement of soil, the height and thewidth of the foot blade of a open caisson and the changes of the properties of soilare analyzed in the process of sinking of open caisson.The value of passive earth pressure on the foot blade of open caisson varies between the value of the earthpressure at rest and the limit value of passive earth pressure. On the basis ofcoefficient of passive earth pressure, the formulas of passive earth pressure onopen caisson and lateral friction of sinking open caisson are given. And thus thecomputing method and experimental formula of sinking coefficient K, and thevalue of side friction ofσf, as well as reference value of earth pressure, are putforward. Then, the computation model of penetration resistance is established. Thecalculation formula and distribution characteristic of the maximum side frictionf₀is submitted. The conclusions obtained in this paper can be used for thereference of other engineering projects.