Site Monitoring And Optimal Design Of Support Combined Anti-Slide Pile With Soil Nail In Loess Slope

At the open excavation of the tunnel entrance in the GuanYinTang of Zhengzhou-Xi'an Railway, the height of the slope is up to 42.5m. During the construction process, the slopes on both sides of the tunnel collapsed several times, and the designing institute redesigned the slope with new reinforcement structure. Anti-slide piles and soil nails were used to support the slope.In order to study the mechanism of action and reinforcing effect of the anti-slide piles and soil nails, the author firstly did a site monitoring about anti-slide piles and the slope. The site monitoring was divided into seven stages which lasts 409 days.According to the site monitoring about the soil pressure, the displacement and the internal forces of the piles, it can be drawed the following conclusions:â‘ With the increase of excavation depth and the time growth, the displacement of piles increase unceasingly.â‘¡Soil pressure behind piles, above the excavation surface, can be seen as a triangle distribution. On the contrary, blow the excavation surface it appears the inverted triangle distribution and trends to decrease with the excavation depth increasing, while Soil pressure before piles increase or decrease along depth of piles.â‘¢the potential sliding surface of slope above the pile is a circular slip surface, while the potential sliding surface between the piles is similar to "0.3H" broken line slide face which can be summarized as "0.4H" broken line slide face broken line sliding surface.â‘£Through the site monitoring about internal force of anti-slide piles and Axial stress of soil nails, it can be find that the design of the anti-slide pile is very conservative.In order to find out the shortages of the design procedure of anti-slide pile, this thesis employed the "cantilevered-pile method" to recalculate the internal forces of the piles and the results show that the "cantilevered pile method" is feasible to be used in design procedure. But the key is the magnitude of the soil pressure behind the piles. this thesis points out that under the premise of a reliable parameter for the strength of the soil, it is feasible to calculate the remnant thrust according to the "slices method" and distribute the remnant thrust in a triangle behind the anti-slide pile, then design and calculate according to the cantilevered-pile method. The result can be used as the foundation of the engineering project. Anti-slide pile to ensure the overall stability of the slope, therefore, you just simply consider stability of the slope above the piles when conducting optimal design of soil nailing.Based on the above calculation method, the support system of the slope was optimized.