Experimental study on special physical and mechanical properties of white sandstone in North Xinjiang

The white sandstone is a commonly used soil material in the Gobi canal. In order to study its physical and mechanical properties, a series of indoor tests are carried out. The following conclusions are drawn: (1) The white sandstone can be classified as the silty sand, its main mineral composition is quartz sand with the mass percent of 66%, and the clay mineral is montmorillonite and kaolinite, accounting for 17%. The special mineral composition and grain size distribution of the silty sand makes it have special behavior, which is similar to that of sand and clay. Among them, the liquid plastic limit closes to that of the low liquid limit clay. The permeability coefficient is on the order of 10^-6 cm/s, closing to that of silt and clay. (2) Whether it is in loose or dense state, the stress of the white sandstone sand is shown as strain hardening, and no volume dilatation occurs. The cohesion increases significantly with the increasing compaction degree, when the compaction degree is 96%, c=41 kPa, which is close to that of the clay. The internal friction angle has little relation with the compaction degree, which is basically 31.8° under different compaction degrees. (3) The critical state line in the e-lnp space of the white sandstone is the same as that of brittle granular materials such as coral sand and even rockfills. Moreover, the critical state stress ratio is not a constant, but affected by the confining pressure and the initial density. All of those are significantly different from the critical state characteristics of the ordinary sandy soils.