Study Of Slope Vegetation By Soil Test And Numerical Analysis Of Channel Bank Slope Stability

A large number of bank slope regulation projects of inland waterway will beperformed in recent years with the government’s policy on internal rivertransportation. During the construction of green channel, it’s crucial to figure out howto keep the shipping lanes open and safe without damage to the ecologicalenvironment along the channel. The slope vegetation, which is effective in bank slopestabilization and environment preservation, has been widely used in regulationprojects of bank slope in the last decades. Because few are known about vegetationroots-reinforced soil strength mechanism, no effective evaluation of change in soilshear strength under slope protection has been conducted till now. As a result, furtherdevelopment of the slope vegetation technique is constrained. The periodic changes ofwater level can be observed in channel bank. Unsaturated and unsteady seepagehappen occasionally. There is few similar article or relevant research oncomprehensive analysis of bank slope stability under the influence of various factorsof unsaturated unsteady seepage. Therefore, there is not sufficient referenceinformation for the evaluation of bank slope stability in water level dropdowncondition.Based on the research background and combined with Guangxi Naji reservoir bankslope regulation project, this paper conducted the following research withexperimental test and numerical analysis method.(1) The triaxial shear tests on undisturbed roots-reinforced soil and disturbed plainsoil samples were conducted by using the SLB-1type triaxial apparatus. On the basisof the test results, the stress-strain curve of undisturbed roots-reinforced soil underdifferent conditions was obtained and the influences of different morphology of rootsand root content on roots-reinforced soil strength were analyzed. The results indicatedthat cohesion force value of roots-reinforced soil is higher than that of disturbed plainsoil.(2) The triaxial shear tests on disturbed roots-reinforced soil samples were performedby using the SLB-1type triaxial apparatus. Based on the test results, the differences insoil strength reinforcement effect between undisturbed roots and disturbed roots were quantitatively analyzed and the variation rule of strength value of disturbedroots-reinforced soil was obtained. With the increasing root content, cohesion forcevalue of disturbed roots-reinforced increases until the root content reaching theoptimum value, and then it will reduce gradually.(3) The triaxial seepage shear tests on disturbed roots-reinforced soil and disturbedplain soil samples were performed by using the SLB-1type triaxial apparatus.According to the test results, strength value of disturbed roots-reinforced soil anddisturbed plain soil decreased with rising seepage pressure. The strength decreaseamplitude of disturbed roots-reinforced soil was lower than that of disturbed plain soiland the increasing confining pressure can help to slow the strength decline. The testresults also indicated that permeability coefficient of disturbed roots-reinforced soilwas higher than that of disturbed plain soil at low confining pressure (20kpa), whilepermeability coefficient of disturbed plain soil was greater than that of disturbedroots-reinforced soil at high confining pressure (27kpa,35kpa).(4) With the application of axis parallel translation technique, the matric suctioncharacteristic tests on unsaturated clay were undertaken by using the SLB-1typetriaxial apparatus and pneumatic control device. The soil-water characteristic curve（The corresponding relation curve of matrix suction and moisture content）of soil inconstruction site was obtained, and data points of the curve can be used as underlyingparameters for the numerical model of the analysis of bank slope stability.(5) The finite element software ABAQUS was developed. Through programming theuser subroutine DISP (ABAQUS user-defined boundary condition subroutine) andDLOAD (ABAQUS user-defined load subroutine), an effective simulation of thedeclining process of water level on the bank slope upstream face had been achieved.Based on the numerical model, the bank slope stability was calculated respectivelyunder the conditions of different depths of falling water level, the rate of decline,permeability coefficient and matrix suction.