南票矿区松散层土体结构性参数试验研究

The experimental study on structural parameters of unconsolidated layers soil of Nanpiao mining

为了研究采空区影响下地表建(构)筑物的变形与破坏,必须首先全面认识建(构)筑物地基土的结构力学特性。基于综合结构势理论,利用TSW-40型土壤真三轴仪,以南票矿区松散层土体为研究对象,开展一系列不同围压、含水率和中主应力比条件下的真三轴试验,揭示了真三维应力状态下松散层土体应力比结构性参数的变化规律,建立了结构性参数数学模型。研究结果表明:原状土的q-ε_s曲线呈现出应变软化型、理想弹塑性型和应变硬化型3种典型的状态。重塑土和饱和土q-ε_s曲线一般均表现为应变硬化型。应力比结构性参数m_η随剪应变、含水率、固结围压和中主应力比的增加而降低;剪切作用初始阶段,m_η下降较快,当ε_s达到5%左右后,m_η逐渐趋于平稳,至ε_s=15%时,m_η趋近于1;结构性参数数学模型结果表明,固结围压对m_η影响最大,含水率次之,中主应力比对m_η影响最小。利用所建立的数学模型预测不同试验条件下松散层土体结构性参数变化规律,模型验证结果与试验结果吻合,证明了模型的有效性,可以作为进一步研究的理论基础。

The structural and mechanical properties of the soil foundations on the construction site are critical for the investigation on the deformation and failure of structures in the goaf region. A series of true triaxial tests on the unconsolidated soils from Nanpiao mining area was conducted using TSW-40 apparatus. The variations of stress ratio and structural parameters of unconsolidated layers soil under true 3D stress state were measured under different conditions of the confining pressure, the moisture content and the intermediate principal stress ratio. A mathematical model of the structural parameters was established. The results show that undisturbed soft present three types of relationships between q and ~, i.e., strain softening, ideal elastoplasticity, and strain hardening. However, the remolded soil and saturated soil exhibit strain-hardening type of q-~ relationship. The structural parameters mn decrease with increasing the shearing strain, moisture content, confining pressures, and intermediate principal stress ratio. In hhe initial stage of sheafing, the structural parameter mn decreases significantly. Then mn tends to be stable gradually as ~ is equal to 5%. The mn equals to 1 When ~s equals 15%. The proposed mathematical model shows that of the number ofmn is significantly dependent on confining pressures, whereas less sensitive to the moisture content, and the intermediate principal stress ratio. The proposed model describes well on the structural parameter of unconsolidated soils under different experimental conditions, and compares well with the experimental measurements.