Research On Evolution Of Earth Pressure Against Retaining Wall In Deep Excavation

With the acceleration of urbanization in China,the number of excavation projects has increased.Pile anchor support is widely used in various deep excavations due to its low cost,simple construction,and good support effect.However,due to the complex distribution of earth pressure behind piles,the distribution of earth pressure behind piles given by classical earth pressure theory often does not match the actual situation,and direct application has certain irrationality.Combined with experience,it is often too safe to cause material waste.Therefore,based on the actual measurement of engineering earth pressure,this article studies the earth pressure of pile anchored deep excavations from the perspectives of numerical simulation and theoretical analysis.The main work and conclusions are as follows:(1)A earth pressure gauge was installed using the jacking method to test the deep excavation in the sandy soil of the Weihe River terrace in Xi’an.The test results were analyzed from the perspectives of apparent earth pressure and total earth pressure.Based on the excavation project,a numerical model was established and analyzed.It was found that the apparent earth pressure distribution proposed by Tschebotarioff and FHWA is in good agreement with the actual measurement,and under the action of prestressed anchor cables,the earth pressure distribution behind the pile is approximately an "R" shape.(2)Based on the PLAXIS software,a two-dimensional numerical analysis was conducted on a deep excavation with single anchor support.It was found that the deformation of the pile body under the single anchor support form is a drum deformation,and the distribution of earth pressure behind the pile is an "R" shaped distribution with the top greater than the static earth pressure and the bottom less than the static earth pressure.The anchoring position affects the stress concentration,distribution,size,and range of earth pressure behind the pile.As the anchoring position moves downwards,the degree of earth pressure stress concentration tends to flatten,and the range of stress concentration becomes larger.The distribution shape of earth pressure behind the pile transitions from an "R" shape to a concave type,and the sliding surface of the excavation in the limit state is an arc shape,close to the distribution of Coulomb sliding surface.(3)Taking into account the equivalent friction angles between layers under different displacement modes,a theoretical analysis was conducted on the ultimate state earth pressure under single anchor support using the horizontal stratification method.The method presented in this paper can represent the "R" type distribution of earth pressure,and compared with previous methods,the calculated results are closer to experimental data.(4)The intermediate state coefficient is used to quantify the non limit state of the pile body,and based on the relationship between friction angle and displacement,a theoretical solution for the distribution of earth pressure in the non limit state under the single anchor support form is provided.The calculated results fit well with the experimental results.As the coefficient of intermediate state increases,the earth pressure on the pile decreases,while the height of the combined force point increases and remains higher than the height of the Coulomb combined force point.