Study On The Deformation Mechanism Of Deposit Disturbance Zone And New Supporting Method Of Anti-slide Piles

In terms of road engineering in a mountainous area,in order to meet requirements of deployment for certain purposes,certain parts of deposit slopes need to be excavated to change the form of slopes and readjust the slope's stress so as to form a disturbance zone.Owing to unloading deformation as a result of excavation of deposit slopes,the disturbance zone has an apparent unloading damage effect,accompanied by the characteristics of porosity development and strong permeability.The rainfall has a critical effect upon the stability of the deposit slope.Therefore,systematic study is necessary because the disturbance zone of the deposit slope need to be quite different from common deposit slope in property,leading to a big disparity in deformation mechanism,deformation features and support design.Based on this,the paper carried out a research on the deformation mechanism,features and new support technology of the deposit slope disturbance zone by means of field investigation,laboratory test,numerical simulation,theoretical analysis and so,combined with the Guizhou Provincial traffic science and technology project of Research on the Technology of Treating Complicated Deposit.The corresponding research progress and achievements are mainly presented as follows.?1?We have investigated the geological features of deposit disturbance zone and tested the mechanical parameters of rock mass.The loose deposit structure is loose with large porosity and strong permeability and apparent interface with the country rock.Ordinarily it remains in an entire state of limit equilibrium but is inclined to slide along with the bedrock-overburden layer interface under the subsequent influences.It has a unique superiority to strengthen the loose deposit slope with anti-slide pile and the rock and soil body has an obvious damage property.?2?We have established a damage constitutive model has been established to describe the forming process of deposit disturbance zone.The forming of deposit disturbance zone is attributed to the unloading damage during excavation.On the basis of this understanding,we customize a damage constitutive model to simulate the mechanism of deposit slope deformation due to excavation with FLAC^3D program and define the cohesion after softening as the function of initial cohesion and plastic strain.We carried out a back analysis for the forming mechanism of the deposit disturbance zone and the result shows the calculation model which has considered the damage softening is fit in with the actual deformation characteristics.?3?We have established a strength reduction model for deposit disturbance zone in the process of water absorption until saturation based on mathematical statistics.Combined with on-site conditions,by means of infinite element modeling,we have analyzed the slope stability,the law of development and change of the slope's strain,displacement and plastic zones during rainfall and the slope stability from the aspects of geotechnical properties,mechanical principles and rainfall conditions.We also discuss the mechanism of slope failure and study the factors affecting the slope of disturbance zone,such as cohesion,friction angle,deformation modulus,Poisson's raio,rainfall intensity,duration of rainfall and slope seepage coefficient.We find the soil strength parameter is the major factor for the slope stability.As the rainwater infiltrates slowly during the rain,the soil strength parameter weakens gradually and so does the slope safety factor until the occurrence of landslide.?4?We have studied the new method for designing the anti-slide piles used to strengthen the deposit disturbance zone based on the calculation theory of point safety factor.The crossover point of the average of point safety factor and the curve of the point safety factor of the sliding zone is called demarcation point and the best location for the piles is on the demarcation point according to the study.So we can decide the best pile locations with the calculation model and point stability factor analysis to make the anti-slide piles work better.?5?We have verified the failure mechanism of deposit disturbance zone and new design method of anti-slide piles by adopting the indoor geomechanical model test and implemented a series of field settlement observation for nearly one year.The results show that the new method for designing the anti-slide piles based on the point safety factor calculation theory has a good significance and can be directly applied in the deposit disturbance zone.