Abstract:

Abstract:  The saprolites derived from crystalline rock and clasolite and developed in slope unsaturated zones are usually sandwiched between residual or colluvial soil and weathered bedrock, and retained large structures such as bedding or fractures from their parent rocks. The color difference between saprolite blocks and their parent rocks is obvious and the texture and structure of the parent rock can be preserved in saprolites. Secondary clay minerals, quartz and ferrohydrite are most common in saprolites. Saprolites have spongy microtexture and are characterized by high porosity, high intrinsic permeability, high specific water capacity, low specific yield and low density. The development of saprolite is realized by the progressive propagation of the weathering front of low permeable rock blocks, and the condensate from the moisture and the unsaturated seepage flow are the key agents of the propagation process. The gaseous water molecules in unsaturated zones spread into the pore system of rock blocks at some depth and condense into liquid water which can dissolve rockforming minerals. In rainy season, the thin water film derived from precipitation on the surface of rock blocks in unsaturated zones absorbs the dissolution components of the rock block solution and carries them into saturated zones. At the same time, the dissolving capacity of solution between mineral grains in rock blocks is also restored. When the above process circulates to some extent, saprolitic crusts will be formed inside structural planes. Saprolitic crusts may absorb and store the liquid water flowing on their surfaces, and in dry season these saprolitic crusts provide unsaturated zones and weathering fronts of rock blocks with moisture. With the lapse of time, saprolitic crusts get thicker and thicker, corestones become smaller and smaller, and finally rock blocks evolve into saprolitic blocks. When all rock blocks within the research area have developed into saprolitic blocks, the rock mass turns into saprolite.

Key words:

Key words: rockmass evolution; slope stability; saprolite; development process