Analysis Of Force Performance And Seismic Resistance Of Sloping Buildings Considering The Skid Resistance Of Engineering Piles

In the traditional design of sloping buildings,the supporting structure is generally separated from the main structure,and there are few related engineering cases of engineering piles and anti-slide piles.Based on the third phase project of Jiujiang Rongchuang Taoyuanli,this paper analyzes the stress and seismic performance of sloping buildings considering the anti-sliding effect of engineering piles.The project is located in Lianxi District,Jiujiang City,where the terrain is high in the east and low in the west.The slope angle of bedrock and site soil is about10.3 ° ～ 12.6 °.After the slope is excavated and filled in different areas,the slope with a height difference of 7 m on the westernmost side of the site is supported by cantilever row piles,and there is also a slope height difference of 9 m in the middle of the site.At this height difference,the basement side wall is used to retain soil.Engineering piles and anti-slide piles are used to maintain the stability of the slope.The main research contents are as follows:1.The most parameters of the HSS model of the soil layer of the site are obtained by the soil test of the dynamic compaction fill of the site.Small strain hardening soil(HSS)and Mohr-Coulomb constitutive model are used to simulate the lateral static load test of single pile,and the numerical simulation results are compared with the field measured data.Because the shear modulus of soil decreases nonlinearly with the increase of strain in HSS constitutive model,the simulation results are slightly better than those of Mohr-Coulomb constitutive model.The applicability of HSS constitutive model in this site is proved.2.In this project,the westernmost supporting pile is constructed first,and then all the engineering piles in the site are constructed,and then the west slope is excavated.During the excavation of the west slope,the west engineering piles in the site participate in anti-sliding,resulting in a bending moment of about 81.The slope in the middle of the site has a height difference of 9 m,and the soil is retained by the side wall of the two-storey basement.The soil pressure on the side wall of the basement is transmitted to the west engineering pile through the bottom plate,and the bending moment of the west engineering pile increases to 180 after the two-storey basement is completed.Due to the existence of engineering piles in the soil on the east side of the side wall of the middle basement,the engineering piles on the east side have a blocking effect,which reduces the soil pressure transmitted to the side wall of the basement to a certain extent.Assuming that the calculated retaining width of the east engineering pile is equal to the pile spacing,the plane finite element model is used to simulate the stress of the east engineering pile according to the construction sequence.The results show that the shielding effect of the engineering pile is obvious within the sliding fracture surface of the soil with a height difference of 9 m,and the maximum bending moment of the engineering pile reaches 422.The structural reinforcement ratio can not meet the stress requirements,so it is necessary to calculate the reinforcement.3.In the plane model,it is too conservative to assume that the calculated retaining width of the engineering pile on the east side is equal to the pile spacing.However,the diameter of the engineering pile on the east side of the basement side wall of this project is 900 mm,and the pile spacing is 5m.In fact,only part of the soil arch effect can be formed,and a considerable part of the soil pressure will leak through the middle of the project pile.Further analysis of the three-dimensional finite element model shows that the actual bending moment of the eastern engineering pile is only 42 ～ 55% of the bending moment of the pile calculated by the plane model,and the engineering pile only plays a partial role in shielding.This project finally adopts the average value of the bending moment of the east engineering pile calculated by the plane model and the three-dimensional model to design the reinforcement.4.In the two conditions of considering and not considering the pile-soil interaction,the dynamic time-history analysis method is used to simulate the seismic response of engineering piles and superstructure,and the results show that the pile-soil interaction has little effect on the seismic response of superstructure under frequent earthquake and rare earthquake.Although the acceleration of rare earthquake is about 7 times of that of frequent earthquake,the bending moment of engineering pile under rare earthquake is only 3.1 ～ 4.1 times of that under frequent earthquake because some soil enters plasticity under rare earthquake.According to the calculation results,engineering piles with diameters of 700 mm,800 mm and900 mm are used in this project,and reinforcement is carried out according to the calculation.The engineering pile and anti-slide pile supporting scheme for the two basements in the middle of the site saves about 25% of the cost compared with the scheme of separating the support from the main body,which has certain economic benefits.