膨胀土侧向膨胀力试验研究与应用

Experimental Study and Application of Lateral Swelling Stress of Expansive Soil

侧向膨胀力是膨胀土支挡结构设计计算中的关键参数。为揭示并表征膨胀变形影响下侧向膨胀力的变化规律,研制二维膨胀仪,提出侧向膨胀力试验方法,以广西百色压实膨胀土为对象,分别研究竖向膨胀和侧向膨胀影响下侧向膨胀力的变化规律,并建立相应的关系表达式。试验结果表明:恒体积浸水条件下,侧向膨胀力与竖向膨胀力之比为0.42;完全侧限条件下,侧向膨胀力会因竖向膨胀的增大而减小;竖向应力通过影响竖向膨胀变形从而间接影响侧向膨胀力;竖向膨胀相关的侧向膨胀力折减系数Df随竖向应力比(竖向应力与竖向膨胀力之比)的变化可用幂函数表征。保持竖向膨胀不变条件下,侧向膨胀力会随侧向应变(侧向膨胀率)的增大而减小;侧向膨胀力越大,最终侧向应变越大;侧向膨胀相关的侧向膨胀力折减系数R随侧向应变比(侧向应变与最终侧向应变之比)的变化亦可用幂函数表征。以浸水条件下大型膨胀土挡墙为例,应用该试验成果分别计算挡墙静止和被推移时的侧向膨胀力沿深度的分布,实测结果验证了计算结果的合理性。提出的侧向膨胀力试验方法和表征公式简单实用,可提高膨胀土支挡结构设计计算中关键参数取值的准确性。

Lateral swelling stress is a key parameter for the design and stability analysis of retaining structures.To obtain and characterize the variation of lateral swelling stress affected by swelling deformation,a two-dimensional swelling apparatus was developed,and a test method for measuring the lateral swelling stress was proposed.A series of tests on compacted specimens of Baise expansive soil were conducted to investigate the change in lateral swelling stress under vertical and lateral swelling deformations;thus,the corresponding expressions were established.The test results show that the ratio of lateral swelling stress to vertical swelling stress is 0.42 under constant volume soaking conditions.The lateral swelling stress decreases due to the increase of vertical swelling ratio under full lateral confinements.The vertical stress affects the lateral swelling stress indirectly by affecting the vertical swelling.The variation of the reduction coefficient(Df)of the lateral swelling stress due to vertical swelling with the verticalstress ratio(i.e.the ratio of vertical stress to vertical swelling stress)can be characterized by apower function.When vertical swelling remains unchanged,the lateral swelling stress decreases with the increase in lateral strain(i.e.lateral swelling strain).Under this condition,the variation of the reduction coefficient(R)of lateral swelling stress due to the lateral swelling deformation with the lateral strain ratio(i.e.the ratio of lateral strain to final lateral strain)can also be characterized by apower function;the greater the lateral swelling stress is,the greater the final lateral strain is.For application,a retaining wall in expansive soil under soaking conditions was selected.Based on the current laboratory test results,the lateral swelling stress distributions along the depth of the retaining wall were calculated at rest and active conditions,respectively.The measured data verify the rationality of the calculated results.The proposed laboratory test method and derived expressions are simple and practical,providing accurate key parameters for the design and stability analysis of retaining structures in expansive soil.