Seepage Characteristics And Fluid-solid Couple Analysis Of Typhoon Precipitation-induced Land Slide In Fujian Province

The coastal areas in Fujian is the focus areas of coastal development, the geological environment of the coastal areas is complex and the geological disasters happened there frequently. As a major regional where typhoon happened, the duration of the heavy rainfall is more than 5 month and the total rainfall can reach as much as 2400-2600mm/y. In the areas where the geological environment is poor,the geological disasters such as collapse, landslide, induced by typhoon, caused serious casualties and property losses and especially the landslide induced by typhoon precipitation called typhoon precipitation-induced landslide. In order to reveal formation mechanism, it is necessary to have a research on the variation of seepage and slope stability.The paper first explains the basic laws of typhoon precipitation-induced landslide from the two aspects of geological environment characteristic of the study region and the basic characteristics of typhoon precipitation-induced landslide. Subsequently, the paper selects the typical slope as testing point, on the basis of understanding soil engineering geological characteristics, artificial rainfall simulation experiment is operated to reveal the variation of saturation, matric suction and soil stress. Further, based on Green-Attempt infiltration theory, combining with the characteristics of typhoon precipitation-induced landslide, the paper analyze the relationship between the rainwater infiltration depth and infiltration time. Finally, combined the unsaturated soil Extended Mohr-Coulomb Criterion,the empirical formula with the strength reduction method, sensitivity analysis method, the paper determines the sensitivity of different disaster-causing factors. The results show that,(1) The material composition characteristics of typhoon precipitation-induced landslide is that the surface part is residual soil accumulation layer and the lower part is breeze or weathered bedrock. The destruction formal characteristic is that typhoon precipitation-induced landslide in the study region is mainly small shallow landslides. The disaster-causing rainfall intensity characteristic is that the induced factors of typhoon precipitation-induced landslide heavy rainfall.(2) The artificial rainfall simulation experiment reveals that soil saturation and pore water pressure increase, but soil stress decrease conversely. The smaller the soil depth is, the larger the variation of saturation, pore water pressure and soil stress is.The larger the soil depth is, the smaller the variation of the monitoring parameters is.(3)The result of fluid-solid couple analysis of typhoon precipitation-induced landslide reveals that rainwater infiltration rate on the slope surface soil before r ain is close to Om/h. In the rainfall region, rainwater infiltration rate at different depths in the duration showed an increased trend, but the increasing point of ra inwater infiltration rate at different depths is not the same. Simultaneously, the in filtration rate increased faster in the early stages of rainfall, and the growth tren d of rainwater infiltration rate become slower along with rainfall. The direction o f rainfall infiltration is mainly vertical slope down firstly, and advance to the slo pe depth gradually. The direction of rainfall infiltration in central rainfall region is still vertical slope down. However, the direction of rainfall infiltration in the f ront areas and rear areas are deflected toward the down slope direction and reve rse slope direction, and the rain occurred respectively lateral flow. After the rain, rainwater spread around in the form of arc sharply.(4) Analyze the stability of typhoon precipitation-induced landslide with a ty pical example, it reveals that during the gradual infiltration of rainwater, the safe ty factor continues to decrease. In the early stages of precipitation, wetting front advance to shallow depth gradually and the slope safety factor reduced slower. In the late rainfall stage, rainwater reachs to the potential sliding surface and the safety factor decrease fastly.(5) Analyze and calculate the sensitivity of typhoon precipitation-induced Ian dslide, it reveals that the impact of matric suction on the safety factor is least. The impact of moisture on slope stability is greatest. The order of significant inf luence of various factors on the factor of safety factor from large to small is wa ter content, effective cohesion, internal friction angle, matrix suction and suction friction angle.