Research And Application On The Erosion Resistance Characteristics Of Remolded Cohesive Soil And Cohesive/non-cohesive Mixtures

The erosion characteristics of geomaterials are widely applied to many water conservancy and civil engineering,such as local scour of pier foundation,channel excavation and dam break problems.Currently,the studies of erosion characteristics of geotechnical materials are mainly focused on coarse particles and fine grain sediment,but for cohesive soils,especially remolded overconsolidated cohesive soils and cohesive/non-cohesive mixtures are deficient.Based on mesomechanics,the force and motion characteristics of geomaterial under the water flow were analyzed.The formula and model of critical shear stress for uniform non-cohesive soils and cohesive soils were derived.According to the scour failure characteristic of cohesive soils,the time required for the destruction of cohesive micro mass was defined.By the means of dimensional analysis,the expression of the time of soil loosening and fracture was acquired.Combining with the bed stress distribution regulation and the definition of scour rate,a unified erosion rate formula for soil erosion was obtained.The erosion resistance of two kinds of remolded pure cohesive soils as well as cohesive/non-cohesive mixtures with 20%,40%,60% non-cohesive fraction respectively was tested in Erosion Function Apparatus.In order to ensure that the physical and mechanical properties of soil are relatively stable during the test,a saturated consolidation method was used to prepare remolded samples.The test results were compared with the erosion rate models proposed in this paper.The result shows that the prediction results of proposed model coincide with the trend of erosion rate-shear stress curves obtained from different samples in the tests and with the high degree of anastomosis,which verified the validity of this model.The critical shear stress and erosion coefficient of different soil samples are obtained through regression.The influencing factors of critical shear stress and erosion coefficient were analyzed.According to the test results,the expression of critical shear stress of cohesive soil-sand mixtures was put forward.Combining the IWHR DB dam break model with the erosion rate formula proposed in this study,the applicability of the erosion rate model in dam break procedure was analyzed by using the data of the Tang Jiashan barrier dam break due to overtopping and the overtopping dam break experimental results of a small homogeneous sand dam model.The results show that the erosion rate formula can be used in IWHR DB model to calculate the failure process of dam break caused by overtopping,and the predicted results are in good agreement with the measured values.The sensitivity analysis of parameters of the erosion rate model proposed in this study was carried out.The analysis results show that the parameters of the model can be calculated in the IWHR DB model under a wide variation range,and the results are less sensitive to the parameters,which can be used in the calculation of practical engineering.