Properties of collapsible soil-a case study

摘要

According to engineering-geological and hydrogeological zoning, territory of Kazakhstan can be divided into following parts: Folded areas of Southern Kazakhstan (Tang-Shan; Zaisan; Altai; intermountain, piedmont lowlands); Turan plateau (Piedmont valleys of Chu depression and plains of Shymkent and Karatau), where predominantly collapsible soils form a sufficient stratum. Because of complex regional engineering-geological prospecting and following generalization, research came up with the following; mainly collapsible soils represent lower quaternary wind deposits, loess loams. The analysis reveals that majority of structures in developed areas are built on quaternary soils. Quaternary soils are notable for the variability of physical properties, complexity, and diversity of mechanical characters. Therefore, collapsible soils were chosen as a target of the following research. Mountainous area around Almaty city taken as an experimental zone. The underground water of 40 meters deep is untapped in this region. However, laboratory tests reveal characteristics of loam as following: density- 15-16kN/m~3; porosity-e ＞0.9 and minor mechanical properties. The value of the total settlement is 8.8-73.51 cm. According to the complex seismic zoning map, Almaty city and neighbour areas are adjacent to seismic district "UI-B-2". Section of given area represent in massive highly porous loess loam rested on gravel. According to seismic properties, following soil has the third category, because of high porosity coefficient (e ＞ 0.9). Preliminary retaining wall design reveals that all northern slope prone to landslide. According to physical properties in full saturation stage, the most unfavourable against slope stability is collapsible loam. Retaining wall stability analysis carried out in PLAXIS 2D reveal that slope in a saturated state prone to landslide. For retaining wall stability, physical and mechanical properties in saturated state influence greatly.