有明黏土各向异性固结特性的试验研究

Experimental study of anisotropic consolidation behavior of Ariake clay

由于大多数黏土矿物是片状的,在沉积和随后的固结过程中黏土颗粒和组构单元趋向水平定向排列,使天然沉积黏土呈现各向异性的固结特性。通过垂直切和水平切试样的恒应变速率固结试验研究了日本有明黏土的各向异性固结特性。试验结果表明,水平切试样的先期固结压力pch与垂直切试样的先期固结压力pcv的比值在0.5~1.0之间,主要是因为天然沉积黏土各向异性的屈服轨迹以及垂直切和水平切试样所经历的应力路径不同;在正常固结阶段,水平切试样的固结系数ch与垂直切试样的固结系数cv之比约为1.43,水平切试样的渗透系数kh与垂直切试样的渗透系数kv之比约为1.40,水平切试样的体积压缩系数mh与垂直切试样的体积压缩系数mv基本相等。因此,有明黏土固结系数的各向异性主要是因为渗透系数的各向异性,而渗透系数的各向异性本质上是因为其微观结构的各向异性。

Natural sedimentary clays exhibit anisotropic consolidation properties since most clay minerals are platy and the clay particles and fabric elements tend to be horizontally oriented in the deposition and subsequent consolidation processes.In this paper,the anisotropic consolidation properties of Ariake clay in Japan were studied by the constant rate of strain(CRS)consolidation test using vertically and horizontally cut specimens.The test results show that the ratios of the preconsolidation pressure of horizontally cut specimen(pch)to that of vertically cut specimen(pcv)are in the range from 0.5 to 1.0,which is mainly due to the anisotropic yield locus of natural sedimentary clay and the different stress paths experienced by the vertically and horizontally cut specimens.In the normal consolidation range,the ratio of coefficient of consolidation obtained from horizontally cut specimen(ch)to that from vertically cut specimen(cv)is approximately 1.43,and the ratio of hydraulic conductivity obtained from horizontally cut specimen(kh)to that from vertically cut specimen(kv)is approximately 1.40,while the coefficient of volume compressibility obtained from horizontally cut specimen(mh)is approximately equal to that from vertically cut specimen(mv).Therefore,the anisotropy of coefficient of consolidation of Ariake clay mainly arises from the anisotropy of hydraulic conductivity,which is essentially induced by the anisotropy of microstructure.