Study On Controlling Methods Of Compactive Quality Of Subgrade Filled With Earth-Rock Mixtures

With the extension of highways into mountainous regions in the west, earth-rock mixtures would be enormously used to fill subgrades. The earth-rock mixture is clearly different from fine-grained soil because of the heterogeneous gradation and water content. Therefore, there would be problems about determination of standard dry density, application of test methods and rationality of evaluation targets. In the past, researches have been carried on methods of controlling compactness quality on the basis of the heterogeneous fills in the construction of dams and highways filled with earth-rock mixtures. The test and evaluation methods, however, could not meet the need of construction now, and should be complemented, improved, and perfected. Based on the indoor and field tests, this paper presents the control target and the involved test method.(1) First, using large-scale compaction device manufactured independently, the variation law of the maximum density of earth-rock mixtures has been obtained when the coarse aggregate contents, the maximum grain sizes, grading, compactive efforts, and different treatments of equivalent change. In addition, when the content of coarse grain changes the variation laws of unconfined compressive strength, CBR, rebound modulus have been acquired.(2) According to the mathematics of Gauss, the relationship between body force and surface force of particle has been obtained, and the relationship between macroscopic stress and microcosmic contact force has been established. Adopting amendment coefficient of grain shape, equivalent radius, distribution function of contact density between particles and so on, the relationship between stress and strain of earth-rock mixtures has been derived. In terms of stiffness matrix, the variation law of mechanical behavior has been gained when the influence factors vary.(3) The evaluations have been conducted on the control targets and test methods, which are used in the control of compaction quality of subgrade filled with earth-rock mixtures. According to the relationship between control targets and its suitable ranges, the degree of compactness has been regarded as control target. At the same time, the method of static penetration has been presented to determine the compaction quality of subgrade according to the merits and shortcomings of the test methods used presently and the relationship between bearing capacity and degree of compactness.(4) Referring to degree of compactness as control target, the problem that how to decide the maximum dry density of earth-rock mixtures should be solved. The maximum dry density of earth-rock mixtures has been determined by adopting the...