Analysis Of Failure Mechanism And Stability Of The Soil-rock Mixture

As a special engineering geological body,soil-rock mixture is widely distributed in China.Because of material composition’s particularity,the current domestic and international’s research about of soil-rock mixture concentrate on its physical and mechanical properties. But the study of soil-rock mixture slope is little.In this paper, the main object of study is soil-rock mixture slope in Manas River Basin.With the development of a large number of infrastructure, problems about soil-rock mixture slope will come out, and therefore our research about the stability and instability mechanism of soil-rock mixture slope will make great sense.Around this theme,a series of work were conducted,such as data collection,site investigation, in-situ test and numerical simulation.First, the engineering geology of the basin was analyzed.Secondly, soil-rock mixture’s distribution and causes, basic properties, characteristics of soil-rock mixture slope were analyzed,combined with investigation and existing research data.Then the situ-in horizontal push-shear test was operated,and the test results was analyzed.Finally,the numerical simulation test was operated. Several factor that can influences slope’s stability and instability mechanism was on study,such as rock content,rock distribution, structure of slope.The main conclusions are as follows:(1) On the basis of field investigation,combined with the existing data,the distribution and cause,basic properties of soil-rock mixture,characteristics of soil-rock mixture slope were analyzed. The results show that: soil-rock mixture was widely distributed in alluvial fan and alluvial plain, upper formation of these area is typical dual structure.And it is formed by the action of the river alluvial.As in mountains and hills,soil-rock mixture was banded distribution.It is formed by the action of the river alluvial and gravity accumulation.The soil-rock mixture slope could divided into single structure slope,dual structure slope,ternary structure slope due to slope’s structure.The natural angle of repose is large,the average slope height is 14.1m, the average slope angle is 71.1°.Most slope is stable but little slope’s rock dropped.(2) The situ-in horizontal push-shear test of soil-rock mixture was operated,so its shear strength parameters was gotted,for cohesion c is 16.28 kPa, internal friction angle φ is 44.98°. Shear stress has its peak in the test,and shear stress-shear displacement curve shows a complete stress-strain curve.Shear stress-shear displacement curve could divided into 5 stages:compaction stage, elastic-plastic deformation stage, the initial yield stage, the strain hardening stage and after-destroy stage. Instability path of soil-rock mixture was analyzed, it was found that instability path is around rock.(3) Rock content, rock distribution, structure of slope has a greater impact on slope’s stability and instability mechanism.The stability of slope is increased with the increase of rock content:when rock content is low,the sliding band of slope is arc shape,slope’s failure is in a rotary-type landslide; when rock content is high, slope’s failure is collapse-crack landslide. Due to the different rock distribution, slope’s failure could divided into rotary-type landslide and collapse-crack landslide when rock content is 30%.This is because critical areas has different rock content. Due to the different slope structure,slope’s sliding band could divided into linear and linear-arc shape,but its all translation-type landslide.