Development and application of macroscopic and mesoscopic analytical testing instrument for reinforcement-soil interface characteristics

To analyze the interaction characteristics of soil-reinforcement interface more comprehensively, an experimental instrument for macro-and micro-analysis of interface characteristics of visible reinforced soils was developed and can be used for direct shear and pull-out tests with different geosynthetics and fillers. The instrument improves the size of test box, facilitates the comparative analysis of the two tests, and has an image recording system which enables the microscopic analysis of test process. The direct shear and pull-out tests of geosynthe­tics(geogrid and geotextile) reinforced tailings sand were carried out with the newly developed apparatus. The results show that the interface parameters(pseudo-cohesion and pseudo friction angle) and pseudo-friction coefficient between geogrid and tailings are about 30% larger than those between geotextile and tailings under the two test conditions. The presence or absence of reinforcement mesh has great influence on the interface parameters of reinforcement-tailings under direct shear test, while has more significant influence on the pseudo-cohesion of reinforcement-tailings interface parameters and less on the pseudo friction angle under pull-out test. With the increase of normal stress of macro variable, the porosity of micro parameter decreases while the average contact number increases. The macro phenomenon reflects that the filler particles are compacted and the resistance of reinforcement materials to be overcome increases. The test instrument can better analyze the macro and micro characteristics of reinforced soil interface, and obtain key technical indicators for the design of reinforced structures.