学院论文代写-发生灾害的自然因素

本文讲的是发生灾害的自然因素,降雨诱发的滑坡发生在陡峭的斜坡上,是由于水的渗入以及随之而来的孔隙压力和土体抗剪强度的变化。水是引起边坡破坏的主要因素之一,易使边坡表面材料软化、强度降低,进而增大孔隙水压力,影响边坡的稳定性。如果土壤处于非饱和状态,则破坏是由于降雨入渗造成的。渗透通常是通过计算无限斜坡的渗透系数、安全系数或临界深度来解决的(Collins和Znidarcic, 2004)。本篇代写论文文章由英国论文通AssignmentPass辅导网整理,供大家参考阅读。

Rainfall induced landslides occur on steep slopes owing to water infiltration and subsequent changes in pore pressure and shear strength of the soil. Water is one of the main factors causing slope damage, and it is easy to soften the surface material and to reduce the strength, then increase the pore water pressure and the effects on the slope stability. If the soil is in the unsaturated state, the failure is due to rainfall infiltration. The infiltration typically addressed by calculating the factor, safety or critical depth for an infinite slope to seepage (Collins and Znidarcic, 2004).
Some scholars have pointed out that the most serious environmental factors to the natural slope are persistent rainstorms, which can easily lead the erosion and collapse of the slope. At the same time, the infiltration of rainwater will promote the elevation of groundwater level causing the instability of the slope. The distinction between the erosion and the pore water pressure is illustrated that soil erosion takes place by the removal of the layers of the soil and the pore water pressure is depicted to be the permanent writing point which indicates the minimal point at which the soil is able to hold water (Fredlund and Rahardjo, 1993).
Adverse effects of groundwater on slopes include: water pressure acting on vertical fractures and resulting in horizontal thrusts, which lead the slope to be pushed downward, the pore water pressure (u) effect acting on shallow sliding surfaces that it reduces the effective stress and friction of surface, the ground water acting on the sheeting minerals especially the clay minerals will produce the lubrication action. Then it will cause sliding and it will change the physical and chemical properties of soil and rock, making rock and soil deterioration, reducing strength and finally influencing the stability of the slope (Zhao, He and Wang, 2003).
After the weathering of slope and rocks, the strength is greatly reduced. Thus, the slope lies at one-side that brings about the increasing of erosion and then re-exposed of internal rocks leading to further erosion and weathering.The collapsed ground acceleration caused by the earthquake will increase the sliding force of the slope and reduce the resistance. The horizontal shock wave released by the earthquake will easily destroy the slope which lacks of the lateral shear force (Lu and Godt, 2008).

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