基于孔压静力触探的连云港海相黏土的固结和渗透特性研究

STUDY ON CONSOLIDATION AND PERMEABILITY PROPERTIES OF LIANYUNGANG MARINE CLAY BASED ON PIEZOCONE PENETRATION TEST

针对连云港海相黏土,分别进行室内试验和孔压静力触探原位测试,并通过现场监测资料进行反分析,比较固结参数的差异性。不同方法得到的结果比较表明:孔压静力触探消散试验确定的水平固结系数为(3.0～6.5)×10-3 cm2/s,通常比竖向固结系数高2～4倍;变水头渗透试验得到的水平渗透系数和孔压静力触探测试现场得到的水平渗透系数值一致性很好;反分析得到的水平固结系数值略低于孔压静力触探测试得到的的水平固结系数值。对连云港海相黏土,地基处理设计采用孔压静力触探方法确定的固结参数能很好地符合工程实际。

The coefficient of consolidation and coefficient of permeability of the Lianyungang marine clay are studied by laboratory and piezocone penetration test（CPTU） in order to evaluate the consolidation and permeability characteristics.The horizontal coefficient of consolidation ch of the clay is also back analyzed according to field data of monitored settlement.Comparisons of the results obtained by different methods indicate that the values of horizontal consolidation coefficients determined by CPTU are in the range of（3.0–6.5）×10-3 cm2/s,typically 2–4 times higher than those of vertical consolidation coefficients.The value of horizontal consolidation coefficient with back analysis is slightly lower than that deduced from CPTU based on Teh and Houlsby′s method.It could be possible due to the smear effect incurred during the installation of the vertical drains.For Lianyungang marine clay,it is recommended that Teh and Houlsby′s method,which takes the rigidity index into consideration,should be used.The coefficient of permeability of Lianyungang marine clay is in the order of 10-6–10-8 cm/s.The value of horizontal permeability coefficient measured by falling-head permeability tests agrees well with that determined by CPTU.It can be indicated when the vertical drains are used in Lianyungang marine clay,the smear effect on consolidation properties of soil has to be taken into consideration in the soil improvement design.For soil improvement schemes of the Lianyungang marine clay,the coefficient of consolidation determined by CPTU dissipation tests is recommended in practice.