Study on the Mechanical Properties of Deep Overburden

The pressure meter is used to do field pressure test on the 15 drill holes in the 4 deep overburden layers where high earth-rock dam is planned to be built, totally 102 reasonable experiment data is obtained with the maximum depth of 85.0m and the maximum test pressure of 4MPa, which is a relatively accurate reflection of the engineering mechanical properties of deep overburden layer as well as its distribution rules. According to the comparison between compression modulus, the laboratory compression test and the field pressure meter test results of deep overburden layer are analyzed. It´s found that the difference between the two is obvious, and with the increasing depth of overburden layer, the compression modulus value by laboratory test is significantly smaller than that by the field pressure meter test. It´s difficult to accurately determine the engineering mechanical properties and the distribution rules of deep overburden layer by the laboratory test. While the pressure meter test, as an effective method to measure the engineering mechanical properties of deep overburden layer, can avoid the loss of structural strength and the influence of scale effect caused by the disturbance of sampling, therefore it can better reflect such characteristics of the overburden layer as complex structural layers, discontinuous rock stratum, alternation of different sizes of gravels, the phenomena of discontinuous grading of open work boulder, the lenses easily to be horizontally aligned or irregular dissection, etc.