Oblique shear method for determining strength performance of pre-compacted very coarse soils
The relevance of the work. Crushed stone, crushed rock and very coarse (mostly crushed plant) soils are the most widely used in the construction of open pit haul roads. However, the strength performance of these media has been studied insufficiently, due, inter alia, to the fact that there are no reliable methods for their determination. The purpose of the work is to develop a reliable method for determining the strength performance of pre-compacted crushed stone, crushed rock and very coarse soils. Research methods. To achieve the purpose, an analysis of the design features of the existing oblique shear apparatus was carried out, elements and nodes were identified that needed refinement to ensure test media pre-compaction, a statistical analysis of the data obtained on the improved oblique shear apparatus, as well as their comparison with the results obtained by testing according to standard methods, were performed. Research results. A design of an improved oblique shear apparatus has been developed, which allows determining the strength performance of statically and dynamically pre-compacted crushed stone, crushed rock and very coarse soils. The required geometric parameters of its individual elements are determined depending on the maximum particle size of the test media, and the order of preparation for the experiment and its conduct is given. Conclusions. The proposed design of an improved oblique shear apparatus allows determining the strength performance of pre-compacted crushed stone, crushed rock and very coarse soils with a particle size of up to 20-30 mm. In order to avoid the occurrence of a keyway effect and to obtain chaotic results, the optimal clearance between the upper and lower holders should be 0.3 of the maximum particle size. To obtain the confidence interval of the measured breaking load value ±10% of the weighted average value with a confidence level of 90% when implementing the oblique shear method, taking into account possible misses, it is necessary to repeat the experiment with the same factors at least 5 times.