Study On Seepage And Mechanical Characteristics Of Soil-Rock Composite Under Rainfall

In recent years, infrastructure construction is developing quickly inour country.Along with the road scale expanding, a large number of slopestability problems also arise subsequently; many high-rise buildings havebrought issues of deep foundation pit excavation and support. Water playsan important role in slope and foundation pit failure. In the southernregion, there is a class of the soil-rock mixture slope. Compared withgeneral soil or rock slopes, its failure law is different.Soil-rock mixture is a kind of special soil which is different withgeneral soil and fragmentized rock in terms of grain composition. Thatcauses it many characteristics in physical and seepage aspects. This paperresearched soil-rock mixture slope stability under rainfall through themethod of indoor test, model test, numerical simulation combined. Majorachievements have been made in the following aspects.（1）Through the large direct shear test, the strength properties ofsoil-rock mixture were studied with different stone content and watercontent. Research shows that: With water content increasing, the internalfriction angle of soil-rock mixture decreases slowly, its cohesion is fastdeclining; with stone content increasing, cohesion and internal frictionangle of soil-rock mixture is bigger. Compared with change of watercontent, the change of internal friction angle is relatively large under thechange of stone content. But the change of cohesion is just in theopposite.（2） Through the modified permeability test, the permeabilitycoefficient of soil-rock mixture is studied with the different stone content,control density and block stones shape. The results show that: with theamount of stone increasing, the permeability coefficient of soil-rockmixture is almost exponential growth; the bigger the control density, thesmaller the permeability coefficient; compared to macadam, permeabilitycoefficientof soil-rock mixture is larger which its interior is pebble.（3）Through the indoor model test, stability of soil-rock mixtureslope under the rainfall conditions is studied. Research shows that: thesoil pressure changes primarily in the first day of rainfall, later tends to be constant; settlement occurred mainly in the first two days of rainfall, andthe settlement is far greater than that in the period of stopping rainfall;water content changes repeatedly with rainfall and stopping rainfall.Generally speaking, it has a gradually increasing trend.（4） The water infiltration process is simulated through FLACsimulation software. Saturation changing with time is converted tovolumetric water content changing with time, and they were comparedbetween simulated data of volumetric water content and soil pressurewith measured data, the result is consistent with model test.