基于孔压静力触探试验的水运工程土分类方法研究

Soil classification method for port and waterway engineering based on piezocone penetration test

土的工程分类是工程勘察和设计应用的关键问题之一。基于孔压静力触探测试(piezocone penetration test,简称CPTU)原位测试参数进行土分类是高效实用的方法。国内外现有分类方法的名称及标准与我国《水运工程岩土勘察规范》(JTS 133-2013)不符合。因此,建立基于CPTU原位测试参数、符合我国行业标准的土工程分类方法具有重要工程意义。在收集大量国内外水运工程CPTU测试资料的基础上,对比分析了616个间距小于5 m的CPTU测试孔和相应钻孔取样与室内土工试验成果。选择国内外7种常用的CPTU土分类图进行应用比较,发现这些土分类图所采用的应力修正计算方法在考虑浅层土体的有效上覆应力修正时存在一定的缺陷,通过引入新的应力修正方法和修正土分类边界线,建立了适合我国水运工程的CPTU土分类方法。对比应用分析表明,该分类图能够准确地进行水运工程土类划分,尤其适合于软土、粉细砂和中粗砂的划分,可作为我国水运工程的土工程分类方法。

Soil classification is one of the key issues in geotechnical investigation and design.And soil classification based on cone penetration test with pore water pressure measurement(CPTU)is an efficient and pragmatic method.The classification standards of existing methods are not consistent with Chinese code for geotechnical investigation on port and waterway engineering(JTS133-2013).Therefore,developing a CPTU-based soil classification method for port and waterway engineering is an urgent and meaningful task.This objective is achieved in this study by collecting database from a large number of worldwide water transportation projects including 616 CPTU and corresponding sampling boreholes,with spacing less than 5 m between them,and comparing and analyzing data and corresponding laboratory test results.Seven existing CPTU-based soil classification charts are selected for performance evaluation using the compiled CPTU and soil type database.It is shown that the stress normalization methods employed in existing soil classification charts may have limitation in shallow soils.A more adequate CPTU-based soil classification method is developed by introduction of new stress normalization method and modification of zone boundaries.It is implied that the proposed method can properly describe the general variation of soil types from CPTU data,particularly for soft soils,silty or fine sands and medium to coarse sands.And the developed CPTU-based soil classification method will provide a more accurate result as compared other existing methods in Chinese port and waterway engineering.