Experimental And Numerical Investigation Of Slope Stability With Multiple Factors Based On Vegetation Protection

The stability of the soil slope of inland waterways is affected by perennial seepage,ship wave and rainfall.In order to prevent the instability of the slope to maintain the navigation safety,treatment should be taken against the dangerous states.As a technology benefiting both slope reinforcement and environmental protection,the slope vegetation has been widely used in regulation projects in recent decades.For the research on slope stability with multiple factors based on vegetation protection,the current research results didn't involve the discriminating standard about the influence of roots on slope shallow stability and the dynamic characteristics of grassroots reinforced soil under the action of ship wave.In addition,some research results were not perfect,which were the influence of seepage damaging on soil structural,slope strength reduction with ship wave and the analysis about vegetation coverage influencing on slope stability with rainfall.In this paper,soil tests combined with numerical simulation techniques were conducted,for the study of slope stability with seepage,ship wave and rainfall based on vegetation protection.The main work includes the following aspects:(1)Triaxial compression tests with seepage of undisturbed and remolded soil were carried out,in which the influence of seepage on soil effective stress strength indexes were classified,that were invariable effective angle of internal friction and decreasing effective cohesion.On this basis,the penetration destruction to the soil structure was quantified expressed as a form of “the reduction of the equivalent confining pressure".In addition,exponential functions were presented to characterize the effective stress intensity with hydraulic gradient change.(2)Triaxial compression tests with seepage of remodeled grassroots-reinforced soil(RGRS)were carried out,in which the effects of roots on the soil permeability and strength were analyzed,and the formula for calculating the depth of considering the seepage damage to the strength of grassroots reinforced soil was derived.(3)Dynamic triaxial tests of remodeled soil and RGRS were carried out.The developmental laws of pore pressure and residual strain were studied.The roots' roles were reducing the pore pressure and residual strain in the process of circulation.Moreover,the formula of shear strength reduction rate changing with dynamic stress ratio of RGRS after cycle was presented.(4)The improved Duncan-Chang model which considers the seepage damage on soil effective stress intensity was conducted on the basis of tests.And for overall stability,the energy integral change in dangerous circular slip zone was used as the instability criterion.The sum of the deformation energy in the area with vegetation roots was used as the indicator to determine roots' function.The study provides theoretical basis for the comprehensive analysis of overall and local slope stability under the action of seepage.(5)Based on the formulas of shear strength reduction rate changing with dynamic stress ratio,through the secondary development of software,the weakening model of shear strength indexes was set up.In addition,the state when the maximal displacement jumped was regarded as instability state.Accordingly,the instability modes were figured out with different ship waves.Consequently,the study provides theoretical basis for the research on the slope with herbaceous vegetation protection resisting dynamic damage.(6)Numerical analysis model of slope stability with rainfall based on vegetation protection which fully considered overland flow erosion and the influence of vegetation coverage was established.The development of plastic zone in the surface layer before whole circular sliding instability was used for characterizing the effect of rainfall on slope stability.(7)The slope stability analysis methods proposed by this paper were used to analyze the soil slope stability with different seepage,ship wave and rainfall conditions.Roots play a role in resisting slope surface deformation.There are large deformations near the water level and slope toe,so these two areas are needed to be strengthened by ecological and engineering protection measures.The surface damage area increases with reduced vegetation coverage and extended rainfall time,so the plastic failure zone in the surface layer is also needed to be strengthened by ecological and engineering protection measures.