| Longnan is the only area in Gansu Province that belongs to the Yangtze River system and has a subtropical climate.It is known as "Longshang Jiangnan".Alpine,valley,hilly,basin crisscross,steep mountains,earth-rock mountainous areas,and heavy rain,and even landslides,debris flows and earthquake disasters occur every year,seriously endangering China’s four major landslides and debris flows concentrated high-incidence areas,is currently plagued by regional economic development and people’s lives and property safety of the main disasters.With the rapid development of urban construction in recent years,the construction of Longnan City in various fields has developed vigorously.However,the unique landform and geological conditions of Longnan City have brought great difficulties to the design and construction of civil engineering,especially the stability analysis and treatment of slope has become a very important research topic of geotechnical engineering and geological engineering.Based on the analysis of site engineering geological conditions and landslides,this paper studies the engineering geological conditions of Longcheng No.3 Slope and its adjacent foundation pit in Longnan City Phase I Project in detail through the pre-geological investigation report,field investigation and test,analyses various factors affecting the slope stability,summarizes and counts the in-situ test indexes and the possibility of the slope.Patterns of destruction.Then,the simplified Bishop method is used to model and analyze the slope stability calculation.In the slope stability calculation model,the ultimate goal is achieved by solving the slope safety factor.Through the establishment of the model,the selection of parameters and the selection of calculation conditions,the calculation results of slope stability are finally obtained.According to the calculation results of slope stability,the slope of the case project is unstable.Based on the result that the slope of the case project is unstable slope,the foundation pit support and slope support scheme of the case project are studied.Foundation pit support is mainly based on the general situation of the surrounding environment of the foundation pit,analyzing the road,building location and foundation characteristics around the foundation pit,taking into account the construction space,construction personnel placement and construction load and other factors,combining with the slope and foundation pit engineering geological conditions,the "pile anchor" supporting measures are adopted.Considering the geological conditions,environmental requirements and surrounding slope conditions,the slope support mainly adopts the support measures of step-by-step slope drainage + pre-stressed bolt(cable)lattice structure.For the high fill slope,the slope support adopts the scheme of setting up buttressed retaining wall at the lower part and pre-stressed bolt lattice structure at the middleand upper part of the slope;for the excavated slope,the slope support adopts the step-by-step slope drainage + pre-stressed structure.The way of force bolt(cable)lattice.Based on the scheme of foundation pit support and slope support,the method of combined support of foundation pit and slope is proposed for case engineering.Through the study and analysis of the stress mechanism of existing double-row pile support,a practical calculation model of double-row pile support structure is put forward.At the same time,the single-row pile support structure is used in some areas of case engineering,and the single-row pile and double-row pile support structure are compared.Feasibility.The design scheme and principle of combined support in case engineering are discussed,but the working condition information and anti-overturning stability of calculation models of row piles and double row piles are discussed.Finally,all kinds of stability are checked and the results satisfy the requirements of the code are obtained. |
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