抄録
The delayed compression and progressive failure of a saturated assembly of crushed mudstone pebbles that occur under constant load application are presented and concluded to be the results of the"slaking"of the mudstone pebbles. The mudstone itself is first idealized as a heavily overconsolidated clay, and the slaking is interpreted as softening behavior with swelling under shear stress application. Due to the slaking, overconsolidated mudstone pebbles tend to return from the initial stiff solid state to a previous, almost normally consolidated soft clayey state. The occurrence of excess shear stress between pebbles is considered to occur possibly due to the concentrated contact forces between them. To substantiate this, one-dimensional compression tests and triaxial compression tests are carried out on the assembly of crushed mudstone pebbles. Although this assembly is to be submerged in water, the individual mudstone pebble itself may initially be in a dry, unsaturated, or saturated condition. The main results obtained through experiment are as follows. (1) The one-dimensional compression tests show that states of the loose specimens in e∼σv space move down gradually towards the normal consolidation line of the clay that was remolded from the mudstones. To prevent long lasting large settlements, it is necessary for the assembly of mudstones to be compacted densely to get their overall void ratio below the normal consolidation line. (2) Even packed densely, the assembly still exhibits progressive failure with time under high shear stress application. (3) Both the delayed settlement and the progressive failure mentioned above are caused by the slaking of mudstone pebbles that could occur due to high contact force concentration between pebbles' boundaries. (4) When mudstone pebbles are initially in unsaturated or dry condition, slaking occurs at a faster rate compared with the saturated case.
