Comparison of Strength and Deformation of Artificially Frozen Soil in Two Testing Manners
MA Wei,\ CHANG Xiao-xiao (State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, China)
With the extensive use of artificial ground freezing technology in construction of mines and deepening of sinking shafts, many engineering accidents occur. A study of frozen soil mechanics in deep alluvium was carried out. The mechanical test method for frozen soil in artificial ground freezing engineering should be first consolidated, then frozen under loading, finally tested (consolidated-frozen-tested or K\-0DCF manner). It differs from traditional test method of frozen soil mechanics, which is first frozen without load, then consolidated, finally tested (frozen-consolidated-tested or FC manner). Tests show strength of frozen soil changing with test methods. Based on the traditional test method of frozen soil mechanics, a lot of research results have been obtained. In this paper, the difference between traditional test method of frozen soil mechanics and the test method of frozen soil mechanics in deep alluvium is discussed. Again the relation between the K\-0DCF manner and the FC manner is studied, so that the research results in FC manner can be shifted directly to the K\-0DCF manner. For providing reliable test basis for studying frozen soil mechanics in deep alluvium and serving to engineering, this paper will probe into differences of strength and deformation between the K\-0DCF manner and the FC manner through triaxial compressive tests of frozen sandy soil. \ \ It is found that the stress-strain curves have the shape of hyperbola for the two testing manners with different deformation process. The yield strength in the FC manner is obviously less than that in the K\-0DCF manner. In the FC manner, the failure strain is obviously greater than that in the K\-0DCF manner under loading, and is obviously less than that in the K\-0DCF manner under unloading. The Mohr's envelopes all accord with the Mohr-Coulomb's criterion within the range of confining pressure in tests. Regardless of state of loading or unloading, the shear strength in the K\-0DCF manner is greater than that in the FC manner and with normal stress, the difference of shear strength between loading and unloading in the K\-0DCF manner is less than that in the FC manner. Yield strength, failure strain and shear strength in the two testing manners can be joined together through equations (5), (6) and (8).
【Fund】： 国家自然科学基金项目 ( 4 97710 2 4) ;; 中国科学院知识创新工程重大项目 (KZCX2 -30 6 )
【CateGory Index】： P642.14
【CateGory Index】： P642.14