Cracking Failure Mechanism And Engineering Application Of Banded Phosphate Rock

The excavation and construction of underground geotechnical engineering is an important project for human development,and the research on the destruction mechanism of surrounding rock is a difficult problem in the field of geotechnical engineering.This paper takes the Houping Phosphorus Miner Section of Yichang Xingfa Group as the engineering background.The stability and destruction mechanism of phosphate rock are analyzed in detail from the perspective of multi-aspect macro view,using both indoor physical tests and numerical simulations.Preliminary conclusions are as follows:(1)The tiny cracks inside the rock penetrated by force is the reason of phosphorus block rock destruction forming macroscopic fissure.The experimental results show thatMost of the phosphate rock patterns cracked along the crystal interface between dolomite and gum phosphate,indicating that the crystal interface between dolomite and gum phosphate is the weakest,weaker than the crystal interface between dolomite and dolomite.It is also weaker than the crystal interface between gum phosphate and gum phosphate.(2)The mechanical properties of phosphate rock are greatly affected by the pressure.The peak strength and failure mode of phosphate block samples are changed by different loading types and different sizes of pressure.When the wall pressure is low,the phosphate block shows brittleness,and when the wall pressure is large,the phosphate block shows ductility.The deformation and strength of the phosphate rock can also be significantly affected by the compaction.According to the simulation test,the microcracks always expand in large quantities in a short period of time after peak strength,and different loading types and encircling pressure will affect the total number of microcracks.The development of a large number of micro-cracks inside the phosphate block eventually formed a damaged sliding surface,which is the essential reason for the occurrence of various types of damage in the phosphate block.Therefore,in the construction of similar lithologic sections,attention should be paid to the stress redistribution leading to the destruction of the surrounding rock chamber.(3)Analysis of phosphate block specimens with holes,the way of formingmicro-cracks and the law of development expansion are not much different from those of normal phosphate block samples.The size and direction of the main stress affect the mechanical properties of phosphate rock specimens with holes,its essential reason is the interaction between the hole promoting sample failure and the surrounding pressure preventing sample failure.If the promoting damage of the hole is dominant,the specimen will be destroyed along the X axis;The specimen will be destroyed along the Z axis when the containment damage of the enclosure is dominant.Therefore,when excavating in the area,we should fully consider the effect of the direction of initial stress on the destruction of the roadway,and strengthen the support when necessary to avoid the collapse of the surrounding rock in the cave room.