攀枝花地区冰期膨胀土的工程特性研究

攀枝花地区冰期膨胀土生成于二冰期晚期中更新统冰期,通过室内和现场物理力学试验和分析,揭示攀枝花地区冰期膨胀土的物理力学性质具有很大的离散性,其性质受土体的矿物成分、含水率、裂隙面、埋藏深度、级配、试验条件等因素、条件的影响。试验研究表明:膨胀土中的裂隙面按光滑程度不相同,可分为两种类型,即光滑裂隙面和光滑擦痕裂隙面; 粗粒矿物对胀缩性影响不大,而细粒矿物对胀缩性影响较大; 裸露或近地表,土层风化剧烈,裂隙较发育,膨胀力度就稍大; 同一地区的膨胀土,蒙脱石含量愈高,自由膨胀率愈大,其膨胀等级就愈高; 不同场地内的膨胀土其物理力学性质指标存在一些差异,但差异性较小; 攀枝花冰期膨胀土层的黏粒含量并不大; 不同场地内的膨胀土抗剪强度值变化较大,同一场地内的膨胀土抗剪强度值有起伏; 攀枝花冰期膨胀土多数呈硬塑-坚硬状,自然状态下其抗压变形能力较好,在浸水饱和状态下,膨胀土的承载力几乎成倍数下降。

ENGINEERING PROPERTIES OF EXPANSIVE SOIL FORMED DURING GLACIAL PERIOD AT PANZHIHUA ARE

The expansive soil in Panzhihua region was generated during the Pleistocene glacial period of the second late glacial period.Based on physical and mechanical tests and analysis of laboratory and field,this paper reveals the physical and mechanical properties of the expansive soil.The properties have a great dispersion and are related with many factors including soil mineral composition,moisture content,fracture surface,buried depth,gradation,test conditions.Experimental results show that the fracture surface of the expansive soil can be divided into two types with different smooth degrees.They are the types of smooth fracture surface and smooth surface scratches.Coarse-grained minerals have little effect on the expansion and shrinkage.But fine-grained minerals have a greater impact on the expansion and shrinkage.For exposed or near-surface soils,they have been weathered intensely,,developed more cracks,have larger expansion efforts.For the expansion soil from same site with higher montmorillonite content,it has a greater freedom of expansion,a higher level of expansion.The physical and mechanical property indices of the expansive soils from different sites have limited differences.The clay contents in the expansion soil is not significant.The shear strength values of the expansive soil from different sites can change greatly.The shear strength values of the expansive soil from the same site can have some fluctuations.A majority of the expansive soils are hard plastic to hard state.Their compressive deformation at natural state is small.Their bearing capacity at natural state can be doubly reduced when they are fully saturated.