| Kualiangzi landslide, in Zhongjiang county of Sichuan province, is a typicalgentle-dipped landslide in red rock area of eastern Sichuan, which has experiencedtwo dramatic slide in1949and1981, and it is still in a state of slow slide now. Thedip of Kualiangzi slide surface is only2°-5°, according to the traditional limitequilibrium theory, landslide with such a gentle inclination is difficult to slide,especially the creep deformation without high water pressure in the rear edge cracksin non-flood season, the genetic mechanism still need to explore. It is noteworthy thatgentle-dipped rock landslides often occur in the rock area which is composed by thenear horizontal sandstones and mudstones, such as the landslides group in Wanzhoucity Three Gorges Reservoir Area, the Tiantai village landslides in Xuanhan country,landslide in Yaochangping of Gaoqiao town in Nanjiang county. Therefore, it isnecessary to study strength properties of weak layer targeted in landslide. Kualiangzilandslide initial slip occurs mainly along the slide over the weak shale, presentdeformation mainly slides along the sliding surface formed during the initial slide, sothe deformation mechanism of Kualiangzi landslide studies should be conductedsliding and initial sliding stage separately.(1) Based on the analysis of engineering geological conditions of the landslide area,basic characteristics of landslide and the deformation history of landslide, the landslidedeformation mode classified into horizontal pushing sliding under extreme rainfall,present daily creep deformation and strong deformation under storm conditions.(2) Through the research of softening effect of mudstone in slide body and soil,that contains soil particles on slide-surface. It is founded that mudstone and soil onslide-surface occur softening, dissolution, hydrolysis and other chemical reactionsoccur and sliding soil soaked with water. it to become loose microstructure mineralparticles cementation deterioration in the micro, and shear strength with immersiontime significantly increased incidence of decay in macro. Combined with thesoftening effect of research results and influencing factors analysis of landslidedeformation, the author proposed deformation mechanism under the conditions of extreme rainfall, which is surface water pooling under storm conditions along thecrack surface and translate to groundwater infiltration in the final, when weak layerssoaked in groundwater interaction strength attenuation to a certain extent, while thehigh hydrostatic pressure in cracks and uplift pressure along the sliding surface.Landslides are pushed, along landslide sliding edge cracks after being opened, thewater level decreased rapidly, landslides restore a stable state gradually. The studyshows that slip zone has been soften and mud in to slip soil rather than the originalrock of mudstone structure, when landslide dramatic slide for the first time；the slideis did not occurred in a sudden, but through underground water trapped intensile-groove gradual osmotic to slide-surface forming uplift pressure, groundwatergradually soften and reduce the strength of sliding soil. Therefore the time of slidetends to lag of rainfall procession. And numerical simulation of landslide sliding isused to verify flat-push landslide deformation mechanism under heavy rain.(3) It is found that slip soil, formed shear plane, began to deform slightly lowerthan the residual strength under shear stress, through the experiments of ring shearand creep for slip soil. Combined with the result of experiments the author proposeddeformation mechanism for present daily creep deformation and strong deformationunder conditions of sudden rainstorm slide. That is creep deformation of Kualiangzilandslide occurs under low hydrostatic pressure along the trailing edge of, with thearrival of the flood season, rainfall increases, continued infiltration of surface water,increasing the weight of the slide and the slide with parts of the groundwater levelrises force status changes. After these factors are accumulated to a certain extent,sliding soil deformation rate increased dramatically, with the end of rainy season thengradually stabilized, the stress state in the new phase and recovery to creep.Previously, there have been many scholars doing a lot research on weak layers ofnearly horizontal strata landslide and strength characteristics of rock sliding but veryfew people studied on the strength characteristics of the sliding surface and creepproperties. Research on deformation mechanism of soil creep characteristics on thesliding surface is an innovative point of this article. |
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