青藏公路沿线通信光缆埋设地段冻土工程地质条件及评价

Effect of Confining Pressure on the Dynamic Features of Frozen Silt

青藏公路沿线季节冻土和多年冻土的总长度为７６０ｋｍ。根据气温冻结指数和融化指数可估算最大季节冻结深度和最大季节融化深度。根据含水量划分出５种冻土类型和５个冻胀敏感性等级。提出了光缆埋设若干选线和施工建议。

The relation of stress-strain, dynamic strength, time and vibrating number to failure and rebound dynamic modulus under different confining pressure are discussed based on triaxial compressive tests with constant strain amplitude controlled by constant strain rate in this paper. Confining pressure effect includes effect of enhancing strength and effect of weakening strength. In lower confining pressure the effect of enhancing strength plays a leading role, where dynamic strength increases with increasing of confining pressure; after the confining pressure reaching a limit the effect of weakening strength plays a major role, where dynamic strength decreases with decreasing of confining pressure. As a result, dynamic strength-confining pressure curve is a parabola in shape. One of the principal reasons resulting in above features is that increasing of unfrozen water content and decreasing of basic strength are caused by the drop in freezing temperature of the soil under confining pressure. The deviation of triaxial strength from the Mohr-Coulomb line is in direct proportion to the increased value of unfrozen water content multiplying by the reduced value of basic strength.