Experimental Study Of Effects Of Loess Strength On Moisture Content

The loess is one kind of typical structural soil,generated as a result of its unique environment and the existence of the historical environment,the formation of columnar joints obvious and pore structure,having special structural and sensitiveness of water,influencing loess engineering mechanics directly,that's why the loess mechanics studies particularity.With the strategic plan of Development of the West Regions,the quantity and scale of regional project expand in the loess day by day;making it is very important to study the unsaturated loess characteristic.The paper finishes different testing with two places loess of Shaanxi and Henan,through the static's test of the original state loess,saturation loess and compactive loess,having the further investigated to unsaturated loess of structural and strength characteristic.First of all,on the foundation of analysing the loess structural mechanism,discuss the moisture content with shear strength through changing the moisture content of the original state loess and finishing shear test directly,indicate:As the moisture content increases,the shear strength present the downward trend,cementation strength and moisture content and present the index relation,angle of friction and moisture content present the line sexual relations,find that the moisture content has more greatly sensitivity than the angle of friction in cohesion.Original sample moisture content increased from 19%to 23%when the lower cohesion larger,reaching 85%;from 23%to 27%increase,the lower the rate of cohesion is relatively small,with the water gradually increased cohesion will tend to zero.Cohesion of comp active loess the relationship between moisture content curve"Z"shape,the characteristics of the moisture content in the = 14%,16%; friction angle and moisture content relationship was quadratic polynomial.The shear strength of comp active remodeling loess showed a downward trend when the dry density decreased;friction angle increase with age was first lowered growth and more stable state;cohesion increases with the age increase.Making the original state loess and compactive loess structural strength under of different round pressure,moisture content of loess and give play to the course through 3 axle shear test,indicate:Unless with round pressure increasing,original state loess structure strength tend towards stability,the stress-strain curve is hardening,as the strain increasing,the strength of body structure of soil accords with Duncan-Change hyperbolic model.Secondly,some key elements,such as the moisture content,density and age,do further through the structural test in the room to find the regulation of strength of structure,finish the moisture content and matric suction relation,Under the same moisture content,dry density of different kind of compactive remodeling is the stress-strain curve is different from that played by the process of structural strength of loess is different.Maximum dry density in compactive remodeling like stress-strain curve of a hardening-type or near-ideal plastic shells.Yellow sticky compactive remodeling cohesion,friction angle and the linear relationship between dry densities. Remodeling is like to compactive loess as a standard sample of the structural parameters of Xie amendment,as the pressure increases,the value of m_p^' reduced and stabilized,soil that is as stress increases in the process,the structural strength is a continuous play.When m_p^' is more than 300kPa of pressure,the more stable soil structure.The results show that the structural parameters are reasonable,and that theoretically m_p^' should be at a later stage return to 1.Test through micro collapse,combine GIS software and divide the shape theory,the hole and particle change the characteristic to draw the loess in the course of falling into collapse,study the quantity soaked with water with fall into the grade regulation wetly in ration.Qualitative analysis: water and collapsible loess closely related,with increasing moisture content,large pores were filled with particles and debris disappear overhead intergranular porosity and pore still exist,with dense granular soil;contacts between particles way by the point-point contact,point-face to face contact with the gradual-change contact;middle like a lesser degree of collapsibility collapsibility obviously like cement;large pores suction generalized reduced gradually close overhead inter-granular porosity and broad pore suction,soil pores become saturated,the reorganization of soil particles are no longer mobile,wet soil subsidence process is complete,more stable soil structure, but the structural strength of the weak;structural deformation for the provision of collapsible space between the suction tablets provide drivers for collapsibility force.Quantitative Analysis:collapsible loess microstructure with the increase in moisture content was reduced porosity,particle aggregation.The quantity and size of the pore size of the number of particles is defined as the ratio of k,the volume of water derived exponential relationship between w and k,the formula is k=0.5755e^-0.0847w.On the above experimental foundation,combine forefathers about the structural parameter research results,and put forward strength parameter of macrostructure and microstructure on the basis of shear test and micro collapse test,and analyse that two kinds of parameters define according with and feasibility.Use system talk about dynamic idea,express moisture content,hole, particle between change and soil body structure regulation with structural strength,find that the moisture content has greater sensitivity to strength parameter of macro and micro structure.With a gradual increase in the volume of water,if the micro-parameters change slower than that of soil structural stability,porosity and particle size,etc.with less affected by water immersion,which can show a higher structural strength of soil.In contrast,changes in micro-parameters of water baptized fast,that easy collapsibility soil,soil water structural changes easily,then the structural strength is also smaller.Volume of water has a strong sensitivity of micro-parameters.Analysis of macro-and micro-structural strength parameters of structural strength and feasibility of the basis of parameters defined in order to Bertalanffy based on general systems theory to geotechnical engineering system theory as a guide,from the soil of both macro-and micro -combined with the existing structural parameters of research results,to try to establish the structural parameters of the theoretical system of loess research framework for the study of the structural parameters of soil to provide a new idea.On the dynamic use of the system,thus allowing the expression of strength parameters of the structure of moisture content,porosity,particle changes and structural strength of soil between the regulations and found that the moisture content of macro-and micro-structural strength parameters of structural strength parameters have a greater sensitivity.Finally,the combination of Henan Province and West-East Gas Transmission Yanshan Reservoir spillway Zichang paragraph of geological disasters in emerging phenomenon,the use of macro and micro-parameters and structural parameters of the theory parameters analysis and control measures in Henan Province Yanshan Reservoir spillway slope on both sides of the major slump triggered by rainfall,precipitation,slope moisture content lead to increase in intensity of macro-structure parameters change,degradation of soil structure;followed by the design of the slope is too large than the factor of safety not lead to stability.West-East Gas Transmission Zichang above the surface as a result of precipitation,runoff and groundwater the role of subsidence caused by wet soil,micro-structural strength parameters of a sharp reduction of structural strength of soil collapse,emergence of potential erosion,subsidence and cave,and that leads to exposed pipes,overhead and shift phenomenon.