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天然土层静止侧压力系数的确定是岩土工程中一个十分重要的问题。用可以测量侧向应力的K_0固结仪对不同含水率Q_3原状黄土进行侧限压缩试验,分析加载卸载路径、竖向应力及含水率对侧向应力及静止侧压力系数的影响,基于试验结果提出加载时静止土压力系数K_0与竖向应力及含水率关系的表达式。研究结果表明,原状黄土的静止土压力系数值不是常数,且不能用Jaky公式进行预测,而是与竖向应力、含水率及加卸载条件密切相关;加载时K_0随竖向应力的增大而增大且趋于稳定值,卸载时静止土压力系数K_(0OC)随竖向应力的减小而增大,且可能大于1;加载及卸载时静止土压力系数皆随含水率的增大而增大;含水率及竖向应力相同时,卸载时K_(0OC)值比加载时K_0值大。加载时不同含水率原状黄土的K_0与竖向应力关系皆可以用双曲线模式描述,用此模式可以较好地预测K_0值;卸载时K_(0OC)与超固结比间呈幂函数关系,但幂指数不等于前人的建议值。
The determination of static lateral pressure coefficient of natural soil is a very important issue in geotechnical engineering. The unconfined compressive strength of Q_3 undisturbed loess with different water content was tested by K_0 consolidation instrument which can measure lateral stress. The influence of loading and unloading path, vertical stress and moisture content on lateral stress and static lateral pressure coefficient were analyzed. Based on the experimental results The expression of the relationship between the static earth pressure coefficient K_0 and the vertical stress and moisture content is proposed when loading. The results show that the value of still earth pressure coefficient of undisturbed loess is not constant and can not be predicted by Jaky’s formula, but is closely related to vertical stress, moisture content and loading / unloading conditions. When loading, K 0 increases with vertical stress Increases and tends to a stable value. The unloading static earth pressure coefficient K_ (0OC) increases with the decrease of vertical stress, and may be greater than 1. The static earth pressure coefficient at the time of loading and unloading increases with the increase of water content Increases; when the moisture content and vertical stress are the same, the value of K_ (0OC) at unloading is larger than the value of K_0 when loading. The relationship between K_0 and vertical stress of undisturbed loess with different water contents can be described by the hyperbolic model. The K_0 value can be predicted well by this model. When unloaded, the relationship between K_0OC and overconsolidation ratio is a power function, However, the power index does not equal the previous recommendation.