Compactness Testing Technology Of Soil-rock Mixture Subgrade And Its Engineering Application

Soil-rock mixture has been widely used in highway for its great advantages of convenience to obtain and its excellent pavement performance. To ensure the compaction quality of soil-rock mixture, the conventional density test method or the other indirect methods are adopted to test the degree of compaction in practical engineering. However, several problems such as poor precision and low efficiency within these approaches can hardly satisfy the need of quality control and schedule requirements. Thus, a new technique for rapid detection of rock-soil mixture is in urgent demand. Combined with the Project” The automatic rapid detection of degree of compaction and its application of rock-soil mixture roadbed” carried out by the highway administrative bureau of Hunan, this thesis carried out the in-depth research of rock-soil mixture roadbed, which is of great theoretical and practical significance.Firstly, on the basis of the existing compaction detection technology of rock-soil mixture roadbed, the characteristics of the rock-soil mixture roadbed were studied, and then the actual construction conditions were simulated, the laboratory models of rock-soil mixture roadbed were therefore designed according to the similarity theory which were filled under either varied rock contents or varied degrees of compaction. A variety of shapes and sizes of the probes were designed, and a lot of experimental curves were obtained through the static penetration test of both the model tests and the roadbed in practical engineering sections. The laboratory and field test results indicate that the curves are more regular while using the flat circular probesfor static penetration tests, which is also conducive to the establishment of a theoretical model. Test results also revealed that the degree of compaction has great impact on static penetration curveswhich proves the conclusion that static penetration tests is feasible to test compactness.Secondly, based on thestatic penetration test results of the laboratory roadbed model, the loading-deformation mechanism of rock-soil mixture roadbed were analyzed thoroughly,a model describing the porosity ratio and deformation modulus of soil-rock mixture roadbed was developed by correlating porosity parameters(highly related with compactness of roadbed) with deformation modulus parameters(related with deformation modulus). On this basis, considering the characteristics of roadbed deformation modulus changing under loading, an idea of step by step loading and the Boussinesq’s theory aboutsemi-infinite space under concentrated load and distributed load were introduced, and then a calculation model of the vertical settlement was established, followed by a new approach for compactness detection of rock-soil mixture roadbed under concentrated load or distributed load. On the other hand, based on the soil-stone column, the roadbed body caused by static penetration tests wasdivided by isotropic stress and deviatoric stress which were adopted by the generalized Hooke’s Law and Duncan-Chang Model, respectively to establish the roadbed penetration load-displacement analysis model with parameters of the roadbed soil cohesion, internal friction angle, Poisson’s ratio and the initial porosity, etc. Finally, the adaptive genetic simulated annealing algorithm analysis method was introduced to determine the compactness of the roadbed, ascertaining the compactness of roadbed by using static penetration tests.Thirdly, based on the principle of limit analysis and the corresponding assumptions, a calculation model of ultimate bearing capacity of circular foundations was established.Each slide was analyzed for energy dissipation and gravity acting, followed by the principle of conservation of energy, the upper solution of ultimate bearing capacity of circular foundations was derived. Then, on the basis of the corresponding assumptions and correction methods, comparing the upper limit solution of ultimate bearing capacity test with standard test curves,the parameter formula were obtained reflecting the probe diameter changes with depth. Compared with the corrected upper limit solution formula with other test curve In contrast, the mean quality value can be inverse calculated, and then the degree of compaction of test points can be obtained. Consequently, a compactness approach was established based on limit analysis methods.Finally, in accordance with both laboratory and field tests and theoretical analysis, a set of static penetrationtest equipment applicable to field use has been developed,with supported by a complete high-precision data acquisition system and the corresponding analysis calculation software and operational procedures. Then this in-situ rapid detection ofcompactness equipment has been utilized for evaluation of rock-soil mixture roadbed sections ofthe Changsha-Xiangtan Highway. Not only do the test results agree very well with the traditional methods, meeting the engineering requirements, but the detection speed has a dramatic increase as well. It indicates that this approach is feasible and reasonable.