| Landslides occur frequently and cause great damage to the development of social and economic stability and the safety of people's lives and estate in the locality.The great majority of landslides in our country are created immediately or indirectly by rainfall,and the happening of landslide is go hand in hand with rainfall.Therefore,with the Zhangjiayao landslide as the engineering background,geological surveys and drilling were carried out on the Zhangjiayao landslide and find out the hydrological and geological conditions of the landslide.Analyze the cause of the landslide based on the local meteorological and hydrological data.The characters of the loess in the landslide are studied through laboratory tests.The relationship between the change of seepage and stability of Zhangjiayao landslide and rainfall conditions is calculated by finite element method in the two-dimension and three-dimension case.The dynamic change of landslide under different rainfall conditions is studied from three fields of seepage,stress and displacement,and the internal mechanism of landslide instability is analyzed.Meanwhile,quantitative analysis of landslide stability change is carried out based on limit balance method and strength reduction method.At the same time,an I-D warning curve suitable for the landslide is proposed to play an early warning effect on the occurrence of the landslide.The influence of anti-slide piles on the stability of Zhangjiayao landslide under different pile positions,different embedded depths and different pile spacings is studied,and the design parameters of anti-slide piles are optimized to achieve a better treatment effect.The main research results are:(1)Measure the soil-water characteristic curve of landslide loess using the filter paper method.In the meantime,the matching effect of three different common models on the soil water characteristic curve is compared and analyzed.And it is recommended that V-G model is the most suitable model for fitting the SWCC of loess.Through the laboratory direct shear tests,it is found that the shear strength of loess is influenced extraordinarily by its water content.When the moisture content increases,the intensity parameters c and?reduce,and the reduction degree of c is larger.At the same time,the saturated permeability coefficient of loess measured by the variable head permeability test.The range of saturated permeability coefficient is 1.09×10-4-1.92×10-4cm/s.(2)The Morgenstern-Price method is used to calculate the stability coefficients of the four different sections of the landslide in natural state and saturated state.The stability coefficients of landslide in the saturated state are significantly lower than that in the natural state.Among them,the 3-3?and 4-4?sections are in an unstable state,and the rainfall causes local instability and failure of the landslide.(3)Using Geostudio software to calculate the seepage and stability of Zhangjiayao landslide,it is show that with the increase of rainfall duration,the pore water pressure of the soil mass increases and the matrix suction decreases.The unsaturated zone of the landslide body transitions to the saturated zone,and the range of the saturated zone gradually expands.The greater the rainfall intensity,the faster the pore water pressure of the soil increases,and the faster the matrix suction decreases.The slope toe is the first to reach saturation.The vertical effective stress inside the landslide body decreases with the increase of the rainfall duration,and the greater the rainfall intensity,the greater the vertical effective stress reduction and the faster the reduction rate.With the increase of rainfall intensity and rainfall duration,the displacement of landslide increases gradually.With the continuous rainfall,the landslide becomes instability step by step.And because of the increasing rain water,the value of stability coefficient also reduces faster.According to the critical moments of landslide instability with different rainfall intensities,an I-D warning curve is established as the critical rainfall judgment for landslide instability.(4)In order to more truly reflect the influence of terrain and rainfall on Zhangjiayao landslide,a three-dimensional terrain model is established based on CAD,and the variation law of seepage field,stress field and displacement field of Zhangjiayao landslide in three-dimensional state is calculated and analyzed by ABAQUS.The results are basically consistent with those of two-dimensional calculation results,and can better reflect the variation law of seepage and stability of the whole landslide.It is found that rain water infiltration has a great influence on the foot and gentle part of the slope,and it is adverse to the stability of those landslide's part.The reason for this is the rain water gathering and the influence of groundwater.At the same time,the principle of strength reduction is used to compute the landslide stability under different rainfall terms.It is found that the stronger the rain is and the longer the continuous rainfall time is,the worse the stability of landslide is.However,the overall stability coefficient of landslide calculated by three-dimensional method is larger than that calculated by two-dimensional method,so the two-dimensional method is conservative.(5)The study of anti-slide piles shows that when the pile position changes from the slope toe to the slope top,the stability coefficient first increases and then decreases.When the pile position is arranged at 100m away from the slope foot,the stability of the landslide is the best.Meanwhile,the deeper the anti-slide pile is embedded,the better the stability of landslide is.And the larger the pile spacing is,the worse the stability is.The relationship between landslide spacing and stability is negatively correlated.The treatment measures for Zhangjiayao landslide choose a rectangular cross-section anti-slide pile with a size of 2×3m.The pile position should be set at 100m away from the slope foot,the pile spacing should be 5m,and the embedded depth should be 1/3H. |
PDF Full Text Request