基于孔压静力触探的修正土类指数土体分类方法与实例应用

CPTU-based modified soil behavior type index classification method and its application

孔压静力触探(piezocone penetration test,简称CPTU)常被应用于土层划分、土体分类,其各种土体分类方法有一定的适用性和局限性。引用两组实际工程案例,对5种常用的基于CPTU的土体分类图进行了分析比较。分析表明,已有分类图虽然能够区分黏性土和无黏性土,但对于粉质黏土、粉土和粉砂之间的判别均存在较大误差,且多数分类图采用过渡带分类,导致分类结果的准确性偏低。基于Robertson土类指数分类图,根据实际CPTU测试数据分类结果,对土类指数I_(c)进行了修正,将其同心圆模型修正为平行线模型,由此提出一种基于CPTU的修正土类指数土体分类方法。根据对实测数据的应用表明,提出的修正土类指数土体分类方法可以更好地满足土体分类,且能够满足粉质黏土、粉土和粉砂之间的判别。

The piezocone penetration test(CPTU)is widely applied in soil layer division and soil classification.However,its various soil classification methods have certain applicability and limitations.Five common classification charts are analyzed based on two groups of practical engineering cases.The results show that the existing classification chart can well distinguish cohesive soil and non-cohesive soil,but there are certain errors in the discrimination between silty clay,silty and silty sand.Besides,most classification charts adopt the transitional zone method,which will underestimate the classification accuracy.In this study,according to the actual test data classification results,the soil behavior type index I_(c) is modified through the soil behavior type index classification chart by Robertson.As a result,a new method of CPTU based modified soil behavior type index is proposed by modifying the concentric circle model to a parallel line model.The application results show that the proposed classification method can well satisfy the classification of practical engineering soil and the discrimination between silty clay,silty soil and silty sand,respectively.