强结构性天然沉积土的强度变形特性

广泛分布在日本大分县的天然硅藻土是一种令人惊奇的具有正常固结历史的天然沉积结构土，其含水量如豆腐，却硬如石头。由于具有强结构性，其土样不会受到取样及成形过程的扰动影响，能够在室内对其天然状态进行力学性状研究，是一种难得的天然沉积结构性土。采用最大压力达10 MPa的高压三轴仪对天然沉积硅藻土进行试验，以探讨强结构性天然沉积土的力学性状。结果表明，其固结屈服压力达到上覆压力的57倍以上，固结屈服前的压缩曲线是水平的，固结压力达到固结屈服压力时，压缩性突增。强度试验结果显示，处于固结屈服前状态的强度与应力水平无关，而处于固结屈服后状态时其强度包络线与重塑粘土同样为通过原点的直线。

Mechanical behavior of a.strongly-structured natural sedimentary soil

The natural diatomaceous soil widely-deposited in Ohita Prefecture of Japan is a surprising natural sedimentary soil with a normally-consolidated history. Its water content is very high, but its stiffness is so high that it can keep its intact state without suffering from the effects of sample disturbance during sampling and handling. The high quality and strong resistance of soil structure provide a unique chance to investigate the mechanical behavior with intact samples in laboratory. A high-pressure triaxial apparatus is used to perform isotropic consolidation tests and triaxial consolidated undrained shear tests. The results indicate that the compression curve of structured soils is a horizontal line from the initial void ratio in preyield state, and the compressibility changes dramatically in the vicinity of the consolidation yield stress. The strength behavior shows that the strength of structured soils is independent of stress level in preyield state, but the strength envelop in postyield state is a straight line through origin which is similar to that of remolded soils.