A Variation Study Of The High Loess Slope Pre-and Post Excavation Unloading Stability Of A Visibility Along The Freeway In Shanxi

With the rapid development of China’s infrastructure, high-grade and large excavation project carried out in the loess region more and more。high loess slope instability events happened frequently。In this paper, study the variation of high loess slope soil’s mechanical properties and stabilities before and after the excavation unloading.First, make a field survey on a highway in Shanxi Province along the high loess slope, Identify the status of each slope engineering, then select14of them representative high slope, and make a detailed analysis about geological background information and geological environmental conditions.At the same time, on the basis of field engineering geological survey, collect samples of each layer and make conventional soil test、undisturbed soil samples of triaxial shear tests and direct shear tests in the indoor; While, make remodeling repeated direct shear tests of soil samples and direct shear tests of unloading case。Reshape the soil samples repeated direct shear test shows:Different parts of the landslide remodeling peak direct shear tests of soil samples repeatedly, residual shear strength parameters change, Peak shear strength parameters Ccq:=3～20kPa,Φcq=10.8～29.2, Residual shear strength parameters Ccq=2～20kPa,Φcq=9.2～27.70, The same soil samples, sample preparation water content changes in plastic limit and liquid limit, Its peak and the residual shear strength index change little, this shows that the water content has little affect when it is greater than the plastic limit.Through Indoor unloading test, conclude the variation of shear strength of loess unloading conditions as follows:With undisturbed soil preconsolidation pressure unloading in the same unloading residence time increases with the preconsolidation pressure, After unloading, the shear strength also increases. when Preconsolidation pressure is200KPa, soil shear strength reduced with residence time increasing, But this reduced rate of change is gradually reduced, Strength after48hours of unloading no longer significantly reduced, Preconsolidation pressure of the same moisture content soil under the kind of strength in the same unloading residence time increases with the preconsolidation pressure, Also increases the shear strength of soil unloading. Under different moisture content and the same pre-consolidation pressure to unload the load time of soil shear strength law:when Moisture content close to the optimum moisture content, Its shear strength is the largest, when Soil moisture content is less than the optimum water content, Shear strength increases with the increase of moisture content, when soil moisture content is greater than the optimum moisture content, shear strength decreases with the increase of moisture content。At the same time, summarized and analyzed to16observation wells of four high slope, the section monitoring holes S-T curves can be quadratic curve fitting, correlation coefficients above0.8.Finally, make stability analysis using the limit equilibrium method and the finite element method along the slope, and make stability analysis to part of slope considering unloading state, the results of the analysis basically coincide with testing or monitoring results。...