酸性环境对污染土力学性质的影响

为研究水-土化学作用的物理力学效应,人工方法制备经硫酸长期浸泡后造成的3种不同pH环境下的土样试件,通过压缩变形性质、界限含水率和三轴固结不排水试验研究了不同酸性环境对污染土的力学性质和变形特性的影响.结果表明:硫酸浸泡过的土的压缩变形包括土体中孔隙水排出带来的弹性变形,还包括土体结构链接发生破坏和变位引起的塑性变形,导致其压缩量较原状土的压缩量大;pH值越低,硫酸溶液浓度越大,发生溶蚀破坏越剧烈,孔隙比越大,压缩系数越大,压缩模量越小;随着pH值的降低,扩散双电层被稀释,土的可塑性变弱,液限和塑性指数都减小;3种pH环境下土体均表现出应变硬化现象,pH=6.0时土体强度增高,而pH=4.0的土体强度低于蒸馏水浸泡过的土体;这与土壤黏粒部分所含的矿物成分密切相关;随着pH值的降低,土的有效应力路径都向左发生偏转,说明土体中的孔隙水压力的上升值和上升速度越大.

Effects of Acidic Geoenvironmental on the Mechanical Properties of Polluted Soil

In order to reveal the physical mechanics of soil-chemicals-water interaction， soil samples were artificially made in three different pH environments induced by immersed in sulfuric acid solution for a long term to carry out experiments on the compressible and deformable properties， consolidated undrained triaxial test and limit moisture content. Results showed that: the compressive deformation for soils immersed in sulfuric acid solution became greater， including the elastic deformation brought about by the remove of pore water and the plastic deformation resulting from the destruction of the soil structure and the conjugation; the lower the pH， the more the sulfuric acid contents， the severer the chemical corrosion， the greater the void ratio of soil， the greater the compression coefficient， the smaller the compression modulus; the pH reduction led to thinner diffuse double layer， so the plasticity became weaker and liquid limit and plasticity index were smaller; all the soils exhibited strain-hardening in the three different pH environments; the strength slightly increased when the pH of pore fluids decreased to 6.0 but significantly decreased at low pH conditions (pH=4.0)， which is related with the mineral composition of the clay fraction; as the pH decreased， effective stress path deflected towards the left due to greater increment rate of pore water pressure.