玉龙雪山西麓原状冰碛土CT扫描试验研究

Computerized tomography(CT) scanning test research on intact moraine soil on west side of Yulong snow mountain

冰碛土是冰川行进融化过程中漂石、碎石、砂砾、粉土和黏土在毫无分选的条件下快速混杂堆积生成的一种特殊岩土材料,由其引发的工程问题日益受到岩土工程界关注。砾石颗粒细观组构是冰碛土独特沉积历史的反映,直接影响土体的岩土力学性质,但迫于原状冰碛土样极难取得,岩土工程领域迄今罕有研究。对此,采用人工精细切削的方式,成功取得了玉龙雪山西麓原状冰碛土样,并对取回的6块冰碛土原状样进行了CT扫描,首次获得了冰碛土内部真实细观组构图像。借助Matlab对CT图片进行二值化和消噪处理后,运用常规统计方法对冰碛土内砾石颗粒的面含石量、颗粒定向以及颗粒形状等剖面组构指标进行了描述。结果表明,垂直剖面之间的统计数据差异较小,但垂直剖面与水平剖面之间差异较大。

Moraine soil is a kind of special geotechnical material generated by rapid mixed depositing of boulders, gravel, sand, siltand clay without sorting when quaternary glacier moving and melting. Engineering problems caused by moraine soil have attractedmore and more attentions from geotechnical engineering field. Meso-fabric of gravel particles is a reflection of the uniquesedimentary history and directly affects the geotechnical properties of moraine soil. However, subjecting to the hardness of obtainingundisturbed moraine soil samples, there is few researches on it. To change this situation, we succeeded in getting undisturbed morainesoil samples from west Yulong Snow Mountain with delicate manual cutting work. Then the 6 pieces of moraine soil samples arescanned by CT instrument and the real meso-fabric images of intemal moraine soil are obtained for the first time. After binarizationof CT images and de-noising processing with the help of Matlab, section fabric indexes of stone area ratio, grain orientation andparticle shape of moraine soil gravel particles are given with conventional statistical methods. The results show that the differencebetween vertical sections is minor, however the difference between vertical and horizontal sections is significant.