Physical Simulation Study On The Formation Mechanism Of Typhoon Landslide In Wenzhou Region

Typhoon strikes Wenzhou region yearly which lies on the east coast of China, andconsequently causes dramatic losses to the people and nation. Its great destroying is notonly the direct cause for buildings to collapse, fields to be swollen by floods, also theusual inducement for the secondary geological disasters such as landslides, collapsesand debris flows.The writer has concluded the developing characteristics of the typhoon landslidesin Wenzhou, obtained the major influential factors, analyzed the causes, and realizedthe typhoon landslides have a close connection with not only the effects of thegeological environment but also the combination effects of both the strong wind andrainstorm along with typhoon. The writer combined the interior factors and exteriorfactors which affect the stability of slope, and then established the conceptual model.According to the different types of vegetation on the slope, we divided them into treesslope, shrubs slope, and without vegetation growth slope. Consequently, after the studyof the failure process of typhoon landslides under the coupling of the single and multifactors through physical simulation with the similarity principle, the writer got severalconclusions as following:The typhoon landslides are mainly small-scale soil landslides, the volume within1000m3, and the upper part of the body is overburden, and the lower is bedrock.Besides, most of the destroying focuses on the interface between the contact interfaceof them, or on the weak plane inside the soil. Most of the plane shapes are either inround-chair or irregular circular-arc. The gradients of these slope concentrate on20o~40o, and there are different kinds of vegetation on the slope covers.According to the characteristics of the typhoon landslides and the equipmentconditions in the laboratory, the writer referred to the typical typhoon landslide,selected a reasonable similarity coefficient for the experiment according to the similarity principle, designed a working condition with the single rainfall factor thatcan be changed, and a condition under the effect of multi-factor coupling fixed by theorthogonal experiment method.Under the single factor condition, the displacement in the middle of the slopechanges most dramatically, according to the monitoring curves, and that in the upperpart increases with rainfall. There is a consistency between the monitoring curvesthemselves, and the monitoring curves and the experimental phenomena.As for the arbor slopes, when they under the multi-factors coupling conditionespecially the super typhoon rainstorm, the lower part of the slope will see the greatestdisplacement, and the soil mass destroyed severely. The consequence shows that therainstorm gradually soften the soil through the heavy rain, and the typhoon wind loadforces the slope to crack by swaying the arbors which contributes to the infiltration ofrainfall and further soften the soil. Thus the arbors begin to fall down under the windload leading the slope to destroy gradually and the decrement of stability. Thevegetation mainly showed a detrimental effect on the stabilityAs for the shrub slopes, the upper and middle parts of arbor slopes, there is noobvious displacement and experimental phenomena under the multi-factor couplingeffect which mainly due to the fact that it is hard for the typhoon wind load to cause anobvious effect through the vegetation to the slope, meanwhile the crown can resist therain, which will reduce erosion of the slope, and that the roots have the power toreinforce the soil mass, enhance the shear strength and erosion resistibility. Thevegetation showed a beneficial effect on the slope stabilityThe achievements would offer reference to further study on the stability of thetyphoon landslides, and has a significant guidance and reference for the harmfulnessevaluation and risk assessment, forecast and prediction of the typhoon landslides in theheavy stricken regions by typhoon in our country.