| Soft rock is a special kind of the rock medium, which has many engineering properties suchas plasticity, rheological properties, easy to disturbance, expansion, disintegration, because ofthe vulnerability and particularity of soft lithology, the stability of the slope is difficult tocontrol. At the same time most of soft rock is water sensitivity rock, water will greatly changeits physical properties, the softening effect of soft rock with water is one of the importantreasons lead to soft rock slope deformation instability.This paper according to a soft rock slope’s soften test results of RuChen highway, base onthe method of Hoek-Brown standards to study for the soft rock softening rule. Using finiteelement analysis software Geo-studio (seep) and intensity software FLAC3D to analyze theexistence of pore water pressure and transient saturated zone physical and mechanicalparameters of rock mass under the condition of rainfall in the slope, the evolution rule ofside slope failure mode and stability in space and time under the joint action of the change.And take a certain contrast support measures, to provide the reference for soft rock slopeinstability of prediction and taking reasonable support measures. The main conclusions ofresearch that are as follows:(1) According to the difference between the saturated and unsaturated state of rock mass,put forward the soft rock in different water condition has some difference in softening law, soneed to adopt different mathematical relationship to describe. The main consideration of themoisture content of unsaturated condition change for softening effect on the strength;Saturation is main consideration soaking time rock to soft rock the influence of strength.Under certain conditions, especially under the condition of the rock mass of unsaturated,using the three order polynomial rule to describe the soften law has a higher fitting precisioncompared with the index.(2) Along with the growth of the rainfall duration, the suction matrix of the side slopereduced obviously, formed a large area of the transient saturated zone on the top of the slope;Slope under the action of various factors, the area influenced by rainfall of surface appearedtension and shear plastic zone, and the plastic area had a linear relationship with rainfallinfiltration depth. Meanwhile, in rainfall process and rainfall stop within a period of time theslope safety factor are gradually reduced.(3) Based on the soft rock slope under the action of the rainfall showed the characteristicsof shallow slip, the rain influence area of the soft rock slope only uses hallow support willensure the stability of the rain influence area in many factors influence. Contrast with the different length anchoring effects, consider the impact of rainfall to soft rock slope using10meters anchor grouting to support in shallow is safe and economic.(4) The proposed rainfall condition soft rock slope stability analysis method not only canconsider to seepage role in the downhill pore water pressure changes impact on slope stability,but also can express the softening effect of soft rock under water in the slope stability. Whichprovides a new method for the stability analysis of the soft rock slope under rainfall condition. |
