Study On The Strength And Deformation Characteristics Of Compacted Loess And Glass Fiber Reinforced Loess

The special Loess Hilly and gully terrain in Yanan restricts the rapid development of its urbanization process.In order to solve the problem of land use and adapt to the rapid economic development model,the Loess Slope filling project has appeared in Yanan area.A large number of high fill works have changed the original groundwater drainage system,and the mechanical properties of intact loess and compacted loess are different.At present,the deformation and slope stability of high fill have become the key issues in engineering construction.Therefore,it is of great engineering significance to study the strength and deformation characteristics of compacted loess in this area.And the research results have a certain guiding value for the analysis and calculation of the deformation of compacted loess filling foundation.At the same time,how to effectively eliminate the deformation of loess high fill engineering failure and improve the strength of compacted loess has become a key problem in the remove hills and fill gullies construction.Therefore,on the basis of the previous research,this paper combines the existing conditions and takes the loess high fill project in Yanan New Area as the research object.Aiming at the two main factors that affect the deformation and failure of compacted loess,moisture content and compaction degree,the strength and deformation rule of compacted loess under different initial water content and compactness are analyzed by consolidation and non drainage three axis test.In addition,glass fiber is used as the improved reinforcement material for loess high fill to explore the strengthening mechanism of glass fiber reinforced material for compacted loess.The main research results and conclusions of this paper are as follows:?1?The stress-strain curves of compacted loess show the form of S shape,which is an elastoplastic curve.During the shearing process,they generally undergo four stages:nonlinear elastic compaction?OA stage?,linear elasticity?AB stage?,shaping?BC stage?and strain growth?CD stage?.The stress-strain curves of loess reinforced by glass fiber reinforced concrete show a growth type "S" curve.During the shearing process,there are three stages of nonlinear elastic compaction?OA stage?,linear elasticity?AB stage?and plastic strain hardening?BC stage?.?2?The initial modulus E₀,elastic modulus E and secant modulus E50 of compacted loess increase linearly with confining pressure and compaction degree,and linearly decrease with the increase of moisture content.The change trend of the secant modulus Es as the strain increases is hilly.When the secant modulus Es increases linearly with the strain growth to the maximum secant modulus,the secant modulus decreases exponentially with the increase of strain and eventually tends to be stable.With the decrease of water content or the increase of compactness,the failure stress of compacted loess tends to increase linearly,and its increasing amplitude increases with the increase of confining pressure.The yield stress of compacted loess increases linearly with the increase of confining pressure,the degree of compaction and the decrease of water content.With the decrease of water content or the increase of compactness,the failure stress of compacted loess tends to increase linearly,and its increasing amplitude increases with the increase of confining pressure.The yield stress of compacted loess increases linearly with the increase of confining pressure,the degree of compaction and the decrease of water content.In the stress plane of p-q,the critical lines of yield state under different water content and different compactness are linear.?3?With the increase of the degree of compaction and the decrease of water content,the cohesive force and the internal friction angle of the compacted loess will increase.But the influence of water content and compactness on cohesive force is greater than that of internal friction angle.The internal friction angle of compacted loess has a power function relationship with moisture content:?=a+bwc.it has exponential function relationship with compaction uegree;?=a1-b1c1k;cohesion and water content is a power function relation:c=a2-b2wc2.it has a linear relationship with compaction degree.?4?Compared with the compacted loess without reinforcement,the initial modulus and elastic modulus of compacted loess reinforced by glass fiber reinforced concrete increased significantly,and all showed a linear growth relationship with the increase of reinforcement length L and fiber content R.The relationship between the initial modulus EO and the increase of the reinforcement length L and the fiber incorporation R can be expressed as En =?aL + b?R +?a'L + b'?Pa??3/pa?n';The relationship between the elastic modulus of glass fiber reinforced loess with the length of reinforcement L and the content of fiber R is E=?a1?3+mR+i?L+E1+a1RPa??3/pa?a2R2?5?The three-dimensional scatter plot of glass reinforced loess R?L???₁-?₃?ff presents a convex surface form,and the two element composite function equation of failure stress with the length of reinforcement and fiber content is established:??₁-?₃?f=Z0+Be-?R/C+L/D?.Under the different reinforcement length,the surface of the yield state of the glass fiber reinforced loess in the stress space of p-q-R is a parallel quadrilateral plane.The establishment of glass fiber reinforced loess yield formula with the increase of glass fiber reinforcement length L and the fiber content of the R force critical state surface:q= aL+b+aR+cLdp.?6?With the increase of the length of reinforcement and the increase of the amount of fiber,the cohesive force shows a logarithmic relationship.The increase of fiber content is more obvious than the increase of the length of reinforcement on the enhancement of cohesive force.The relationship between the cohesive force of glass fiber reinforced loess and the amount of glass fiber added and the length of reinforcement are established:c=c1+Ke-?L/M+R/N?.Although the internal friction angle increases with the increase of glass fiber content and the increase of reinforcement length,the increase range and growth range are very small.?7?According to the stress-strain curves of s compacted loess in the study area,a typical s type function Logistic function is applied to fit the stress-strain curves,and the stress-strain curve relationship model of compacted loess under different confining pressures is obtained:?8?The reinforcement effect of the fiber mainly depends on the interaction between the fiber and the soil.The relative slip function fm and the strength reinforcement effect coefficient Koare introduced into the stress-strain relationship of compacted loess,and the stress strain relation equation of compacted loess reinforced by glass fiber reinforced concrete is further established:??₁-?₃?= KA₂[1-1/?1+??/fm?50??^p].