Permeability Of Phyllite Talus And Its Influence On Slope Stability

The phyllite talus along the Wenchuan-Maerkang expressway are widely developed.During the rainy season,such deposits are often unstable,causing frequent landslide disasters.When scholars conduct instability model analysis and stability calculation on the phyllite talus,they mostly regard it as homogeneous soil.In fact,phyllite fragments are characterized with flattened shape,and field investigations have shown that the fragments will maintain orientation in the talus.To study the permeability of the talus with orientational characteristics,and to grasp its characteristics and mechanism of seepage failure under the action of seepage has important theoretical significance for further research on the mechanism of rainfall disaster.This article defines "orientation angle" and "orientation rate" to describe the orientation of fragments.The angle between the maximum area of the fragment surface and the horizontal plane is called the orientation angle.If the difference between the tendency of the fragment and the slope angle of the talus is less than or equal to30 °,the fragment is considered to be orientational.The ratio of the mass of the orientational fragment to the total mass of the fragment is called the orientation rate.The permeability of phyllite talus were studied through laboratory tests,and the influence of the permeability of phyllite talus on slope stability was analyzed according to the test results.The main work and results are as follows:(1)In order to make the test instrument accommodate the phyllite with larger particle size to achieve better test results,and in order to better observe the test phenomenon,a large-scale permeability experimental apparatus was designed by myself.Combined with the apparatus,the corresponding test method is proposed,and the effect of the instrument is good.(2)Through the experiment,the influence law of the orientation angle on the permeability of the phyllite talus is obtained: the larger the orientation angle,the easier the sample will appear the phenomenon of fine particles jump and turbidity of the aqueous solution during the sample test.When the orientation angle is 0°,it is the most difficult to cause piping,and then 60°,90° and 30° in sequence;the greater the orientation angle,the greater the permeability coefficient;the orientation angle increases,and the critical hydraulic gradient decreases,and the failure hydraulic gradient decreases first and then increases,then it decreases again.(3)Through the experiment,the influence law of orientation rate on the permeability of the phyllite talus is obtained: the greater the orientation rate,the easier the sample will appear the phenomenon of fine particles jump and turbidity of the aqueous solution during the sample test,and the easier it is to develop piping;the greater the orientation rate,the greater the permeability coefficient;the greater the orientation rate,the critical hydraulic gradient and the failure hydraulic gradient both show a decreasing trend.(4)Through the experiment,the influence law of phyllite content on the permeability of the phyllite talus is obtained: the larger the content,the more difficult the sample is to beat fine particles,the turbidity of the aqueous solution,and the more difficult it is to generate piping;The smaller the content,the greater the permeability coefficient;when the content decreases,the critical hydraulic gradient and the failure hydraulic gradient show a decreasing trend.(5)Through the experiment,the influence law of the phyllite particle size on the permeability of the phyllite talus is obtained: the larger the particle size,the easier the sample is to appear fine particle jumping,aqueous solution turbidity,and the easier it is to generate piping.The smaller the particle size,the smaller the permeability coefficient;when the particle size decreases,the critical hydraulic gradient and failure hydraulic gradient show an increasing trend.(6)Through theoretical calculations,the influence of the phyllite orientation angle on the slope stability under rainstorm is obtained: when the phyllite orientation angle is the same,the longer the storm,the bigger the thickness of the sliding body of the phyllite talus slope.When the rainstorm time is the same,as the orientation angle increases,the thickness of the sliding body gradually increases.(7)Through theoretical calculation,the influence of rain intensity on the slope stability is obtained: under the same rain intensity,the longer the rainfall,the greater the thickness of the sliding body of the phyllite talus slope.When the thickness of the sliding body is the same,the weaker the rain,the longer the rainfall time required.