石家庄地区某场地不同取样方法获取土样的对比分析

采取原状土样是工程勘察中的重要环节,不同的取样方法对土样质量的影响不同。一般认为竖井中采取的大块土样,是"真正"的原状样,钻孔中使用取土器采取的原状样存在不同程度的扰动。在钻孔中采用不同的取样方法,土样受到的扰动程度也不一样。笔者通过对钻孔两种方法获取的土样与竖井土样试验数据的对比发现,钻孔取样对土样有明显的扰动和压密作用,造成了土的干密度增大、孔隙比减小、渗透系数降低、压缩模量增大。同时发现,钻孔快速冲入取样质量略好于上部击入取样质量。为保证工程安全,对常规钻孔取样试验成果的使用应当慎重,对重要工程宜采用探坑、竖井取样,或采用双筒薄壁取土技术。

COMPARATIVE ANALYSIS OF UNDISTURBED SOIL SAMPLE QUALITIES WITH DIFFERENT SAMPLING METHODS IN A SITE IN SHIJIAZHUANG,HEBEI PROVINCE

Primary state soil sampling is an important tache in engineering exploration,different sampling method has different affection to the quality of soil sample.Generally speaking,the big primary soil sample collected in shaft is the true primary state soil sample,the sample collected by soil collected equipment in drilling is of different degree disturbance.The disturbing degree is different with different sampling method in drilling hole.Through comparative analysis to the test data of tow sampling methods in drilling hole and sampling method in shaft,it was found out by the author that the drilling sampling method has obvious disturbance and depression to the soil sample,which caused the soil sample’s dry density to be increased,porosity ratio to be decreased,filtration coefficient to be decreased,and modulus of compression to be increased.Meanwhile,it was found out that the sample quality collected with fast irruptive is slightly better than sample’s quality collected by upper irruptive.In order to ensure the safety of engineering,it should be careful to use the test result of normal drilling sampling,the pitting sampling,shaft sampling,or double-tubles and thin-wall soil collecting methods should be used.