Deterioration Processes And Mechanism Of Phyllite From The Slope Surface In Typical Debris Flow Channel In Zhouqu Region

The region of Zhouqu in the Gansu province is one of the areas with the most intensive development of mudslides in China.Degradation of surface phyllite in debris flow channel in this region under the influence of environmental dynamics is one of the main reasons for the highly development of debris flow in the region.Based on the correlation analysis of engineering geological rock formations and geological disasters in the Zhouqu area,we selected the typical weakly weathered phyllite rock in the study area as the research object.In combination with local meteorological data,according to the factors of precipitation,evaporation,surface temperature,we summarized a total of four types of water-rock degradation conditions,including daily dry-wet condition,common dry-wet condition,extreme dry-wet condition and freeze-thaw condition.After the field investigation and on-site sampling,through testing the physical and mechanical properties of the phyllite after different water-rock interactions cycles maintenance in different times,the results explain the degradation behavior and mechanism of phyllite under different water-rock degradation conditions.(1)According to the past scholars' research and site survey data,We systematically analyzed the geological environment in the debris flow ditch in the study area:(1)Based on the comprehensive study of geological environment conditions in the Zhouqu area,We have discovered that formation lithology is a controlling factor in the frequent occurrence of geological disasters in the region.Then we chose the typical collapse in the debris flow ditch in this area as an example,Emphasis was placed on the analysis of the relationship between collapse,source material of debris flow and the phyllite strata.(2)Based on the systematic analysis of the climate characteristics of Zhouqu,it is concluded that the precipitation and temperature characteristics are the main factors causing the deterioration of phyllite.The main reason for the development of the collapse and debris flow disaster in the study area is that the surface phyllite in the slope of the debris flow ditch has deteriorated under the dry-wet condition and freeze-thaw condition.(2)Based on the qualitative understanding of the relationship between the main factors causing the deterioration of phyllite,degradation and source material of debris flow.Through the observation of the macroscopic observation,quality,stress-strain relationship,uniaxial compressive strength test.The systematic analysis of the degradation of physics and mechanical properties of phyllite after different water-rock degradation condition(daily dry-wet condition,common dry-wetcondition,extreme dry-wet condition and freeze-thaw condition)cycles in different times.With the increase of the number of cycles,the macroscopic morphology,mass,elastic wave velocity,and uniaxial compressive strength of phyllite will significantly deteriorate,and the degradation intensity is in order of extreme dry-wet condition,common dry-wet condition,freeze-thaw condition,daily dry-wet condition.(3)The qualitative analysis of the failure process of phyllite was performed using the related theories of petrology.The quantitative analysis of the parameters of phyllite was performed using the field environment and laboratory tests,our results build a relationship between the deterioration of phyllite and the collapse of slope and the formation of source material of debris flow is described.