磷尾矿改良膨胀土动变形与动强度特性试验研究

Experimental study on dynamic deformation and dynamic strength of expansive soil modified by phosphorus tailings

利用GDS真/动三轴仪,进行磷尾矿掺量0%,3%,7%,11%及围压100,150,200 kPa下的改良膨胀土一系列动三轴试验;探讨不同围压不同磷尾矿掺量对改良膨胀土动应变-动应力(εd-σd)关系、动弹性模量、动强度及其指标变化规律的影响。试验结果表明:改良土ε_d-σ_d曲线随着磷尾矿掺量增多先上移后下降,最优掺量为7%;动弹性模量E_d随动应变ε_d增大而减小,ε_d≤0.2%时,动弹性模量减小迅速,εd>0.2%时,土体进入塑性发展阶段,E_d减小变缓;动强度曲线符合幂函数关系,动强度随围压增大而增大,随磷尾矿掺量增加先增大后减小,相对于纯膨胀土,最大提高约40 kPa,增加量约30%;改良土动黏聚力c_d随磷尾矿掺量先增大后减小,相对于纯膨胀土最大提高约9 kPa,增加量达36%,磷尾矿掺量对动内摩擦角φ_d影响较小。通过非线性拟合动强度参数与磷尾矿掺量关系,给出动强度计算公式。

The ε~d-σ_d relationship,dynamic elastic modulus and dynamic strength was studied under different confining pressure and Phosphorus tailings by GDS dynamic triaxial test.The experimental results show that the dynamic strain-dynamic stress(ε_d-σ_d)curves of the improved soil rise first and then decrease with the increase of phosphorus tailings,and the optimal dosage is 7%.The dynamic elastic modulus E_d decreases with the increase of the dynamic strain ε~d,When ε_d≤-0.2%,the dynamic elastic modulus decreases rapidly.When ε_d>0.2%,the soil enters the plastic development stage,and E_d decreases and becomes slow.The dynamic strength curve conforms to the power function relationship;Dynamic strength increases with the increase of confining pressure,and increases first and then decreases with the increase of phosphorus tailings content.Compared with pure expansive soil,the modified soil dynamic strength increases by about 40 kPa,and the increase is about 30%.The improved soil dynamic cohesion c_d increases first and then decreases with the increase of phosphorus tailings content;Compared with pure expansive soil,c_d increases by about 9 kPa,and the increase is about 36%.The amount of phosphorus tailings has little effect on the internal friction angle φ_d.The dynamic strength calculation formula is given by nonlinearly fitting the relationship between dynamic strength parameters and phosphorus tailings.