Large Scale Field Test of Pumpable Roof Bolts.

摘要

In 1970,the Bureau of Mines began a program of developing and testing a new type of roof bolt now known as the pumpable bolt. The concept embodies the basic principles of the conventional expansion shield type roof bolt and in support mechanism parallels the resin grouted roof or rock bolt. The basic elements of the pumpable bolt are the tension member in the form of strands of continuous fiberglass and a grout or cement in the form of an organic resin. The fiberglass is fed into the bolt hole conventionally drilled in the mine roof and the resin is pumped into this hole to grout the hole and bond the glass strands to the roof rock,thus form a nontensioned bolt. The resin system consists of a catalyzed component and a promoted component. When mixed,these two monomers polymerize into a solid,bonding the glass strands to the roof rock. Based on laboratory tests,the Bureau of Mines reports a tensile strength of the bolt of 40,000to 44,000lb, a shear strength exceeding 13,000lb,and a holding strength of 25,000lb/ft in dry strata. On the basis of these data,the Bureau has undertaken to evaluate the feasibility of the pumpable bolt concept by large-scale field tests in two operating coal mines.