昆明泥炭土工程性质原生各向异性试验研究

基于一系列室内试验结果,系统分析了昆明泥炭土原生各向异性对固结变形、抗剪强度和渗透性质的影响,并从分析泥炭土特殊组分入手,探讨了其工程性质原生各向异性的产生机制。试验结果表明:高分解度泥炭土水平向与垂直向表现出来的变形特性差异不大,θ=45°方向土样在固结压力p较小时压缩模量E_s及固结系数C_v较小,但当p增大到一定程度时,3个方向的变形特性趋于一致;分解度低的泥炭土更多呈现变形各向同性。抗剪强度方面,不含或含微量残余纤维的高分解度泥炭土抗剪强度原生各向异性程度较弱,主要体现在粘聚力上,内摩擦角的差异较小,且抗剪强度各向异性程度随着腐殖质含量增多而减弱;残余纤维含量多对泥炭土的强度各向异性能起增强作用。渗透特性方面,渗透系数k随切样角度θ增大而增大,即泥炭土水平方向的渗透性比垂直方向的强。泥炭土的各向异性机制复杂,在导致各向异性效应方面,矿质土颗粒、腐殖质及残余纤维产生了不同的效果。

Study on the Engineering Properties Inherent Anisotropy Characteristics of Peaty Soil from Kunming

Based on a series of laboratory tests results, the influence of inherent anisotropy on the shear strength, deformation and permeation characteristic of peaty soil from Kunming were studied, and the mechanism was discussed by analyzing the special material composition of peaty soil. Test results show that compression and consolidation behaviors of the amorphous peaty soil sampled both from vertical and horizontal directions are not remarkable. But the amorphous peaty soil, sampled angle θ=45°, modulus of compression E_s and coefficient of consolidation Cv are relatively small when the consolidation pressure p is smaller. The deformation characteristics of three directions are reaching unanimity when the consolidation pressure p becomes large enough. The peat soil with lower decomposition is closer to isotropic in compression and consolidation. The main inherent anisotropy in shear strength are as follows: first, the anisotropy in shear strength is relatively weak. The anisotropy in shear strength is mainly externalized by cohesion but the friction is nearly the same. The anisotropy degree of the shear strength is weakened along with the increase of the content of humus. Second, the content of the residual fibers plays a role in enhancing the shear strength anisotropy performance of the peat soil. The permeability coefficient of peaty soil is increased with sampled angle. The permeability coefficient of peaty soil sampled from vertical is larger than the horizontal directions. The mechanism of inherent anisotropy is extremely complicated, which is the gaming result of the mineral soil particle, humic substances and residual fiber.