| Rainfall infiltration is an important cause of instability on steep loess slopes.Landslides on steep loess slopes will cause significant property losses and casualties.It is of great practical significance to study the instability evolution law and stability control method of steep loess slopes under rainfall conditions.In this thesis,the 4 #high-steep loess slope of Shuo Huang Railway is taken as the research background.Based on the theory of soil seepage,the stress and deformation characteristics of a steep loess slope under rainfall conditions are studied by means of theoretical analysis and numerical simulation.The influence of different factors on slope stability is discussed,and then the instability risk of a 4 # high-steep loess slope is evaluated,and the slope reinforcement methods are compared and selected to provide guidance for the stability protection of a high-steep loess slope.The research contents and conclusions of this thesis are as follows:(1)The failure law of a high-steep loess slope under continuous rainfall is studied.Studies have shown that throughout the rainfall process,the rainwater infiltration rate is negatively correlated with the infiltration depth and duration;shortterm rainfall leads to the slope top water storage infiltration,a greater soil displacement increment than other parts of the slope,and the slope top collapse phenomenon;long-term continuous rainfall leads to the deterioration of the slope,and the displacement of the slope surface is greater than that of the slope top.The slope slips along the slope to the lower left until the plastic zone penetrates and the slope is unstable.The slope safety factor in the process of rainfall is calculated using the strength reduction method.The value is 1.543 at the initial stage of rainfall,1.012 when the rainfall reaches the limit equilibrium of the slope,and 0.881 when the rainfall reaches the instability of the slope.The change process corresponds to the slope instability process.During the whole failure process,the displacement increment of the slope toe is the largest,the stress change is the most obvious,and it is the most vulnerable part of the slope.(2)The influence of six factors such as rainfall intensity,rainfall duration,cohesion,internal friction angle,elastic modulus,and Poisson’s ratio on slope stability is studied.The results show that the influencing factors for slope stability are as follows: Rainfall intensity > rainfall duration > internal friction angle > cohesion.Elastic modulus and Poisson’s ratio have little effect on the safety factor but mainly affect slope displacement.Cohesion,internal friction angle,elastic modulus,and Poisson’s ratio are positively correlated with slope stability.Rainfall intensity and rainfall duration are negatively correlated with slope stability.(3)The rainfall instability risk assessment system for high-steep loess slopes is established.By using the literature research statistics method,the qualitative screening method,and the objective weighting method,the risk evaluation index of slope instability is obtained,and the risk evaluation model of rainfall instability on a high and steep loess slope is constructed.The model includes four first-level evaluation indexes and ten second-level evaluation indexes.The first-level evaluation indexes are stratum lithology,slope geometry,rock mass physical characteristics,and natural environmental factors.The second-level evaluation indexes are the weathering coefficient,rock and soil permeability coefficients,slope height,slope angle,soil cohesion,soil internal friction angle,soil elastic modulus,soil Poisson’s ratio,rainfall duration,and rainfall intensity.(4)The instability risk of a 4 # high and steep loess slope after six days of heavy rainfall was studied.The risk classification standard of the evaluation index is formulated using the relationship between the influencing factors of slope stability and the modified safety factor function,and the fuzzy comprehensive evaluation method is improved.The instability risk of a 4# high and steep loess slope is calculated by the fuzzy comprehensive evaluation theory.The result is that the slope instability risk level is grade IV under heavy rainfall,and the slope is unstable and needs to be reinforced.(5)The anti-slide effects of two slope reinforcement methods,anchor frame beam and anti-slide pile,are compared and studied.The results show that when the slope is reinforced by the anchor frame beam,the anti-sliding time is not increased.In short-term rainfall,the displacement of the protective position is significantly reduced compared with that without protection.When the rainfall reaches the limit state of the slope,the slope slip is reduced by 22.5 cm.When the anti-slide pile is used to reinforce the slope,the anti-slide time is increased by 3 days.In the short term,the displacement of the protective position is not significantly reduced compared with that without protective measures.When the rainfall reaches the limit state of the slope,the slope slip is reduced by 20 cm. |
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