Experimental Research On Piles Supporting Rock And Soil Foundation Pit Slope

Due to its low environmental impact and strong adaptability to the strata, soldier pile retaining structure is widely used in pit slope support project. In the design theory of soldier pile retaining structure, it is assumed that the piles are embedded in soil or rock. In some areas(e.g., Chongqing and Dalian), this is often the case that the soldier piles are embedded in both soft rock and soil, and the embedded length in the soil and in the soft rock is almost equal. Because of the quite different properties of soil and rock, the complex interaction mechanism between the pile and them, there is some difficulty in ignoring the embedded length in soil or rock and simply applying the design theory that assumes the pile is embedded in soil or rock to the design the soldier pie retaining structure that are embedded in that condition. This paper takes a soldier pile retaining pit slope engineering in Chongqing as background, designs a model experiment that simulates the excavation and loading process, of which the foundation pit is retained by soldier piles and the piles are embedded in both soft rock and soil. Based on the result of the experiment, this paper discuss how the existence of the rock, stiffness of the piles, the strength of the soft rock and the embedded length influence the pile lateral pressure, the moments and the displacement of piles' top, which may provide a reference for the design of soldier piles under such geological conditions.In this paper, the main work done is as follows:1According to the test object and the specific experimental conditions, a model experiment of single factor was designed to research how he existence of the rock, stiffness of the piles, the strength of the soft rock and the embedded length influence the pile lateral pressure, the moments and the displacement of pile top. Motor and stainless steel pipe were used to simulate soft rock and retaining piles. By changing the thickness and length of the stainless steel pipe, mix ratio of mortar to simulate the variation of stiffness of retaining piles, the length of retaining piles and the strength of soft rock respectively. A pile that is embedded in full soil was set as comparison.2According to the model results, experimental data were analyzed and the property of how the pile-top displacement, the pile lateral pressure and the moment of the pile vary during the excavation and loading process was obtained. And the law of how he existence of the rock, stiffness of the piles, the strength of the soft rock and the embedded length influence the soil pressure on the pile, the moments and the displacement of pile top during the excavation and loading on the top of the foundation pit process was obtained.3Based on the analysis of experimental data the conclusion presented, some advices were proposed on the design of soldier pile retaining structure that is embedded in both soil and rock.