"We have increased the compressive stress in a predicted volume of rock of roughly 103 cubic feet by slow pumping of a predicted volume of cement (4 cubic ft.) starting from the ambient stress of 850 psi and reaching a desired maximum overstress of 4,500 psi. The tests were conducted in the Bueno Mine, Jamestown, Colorado, at a drift face roughly 850 feet horizontally into the mountain from the portal. A packer was set 5 feet into a 6 foot drill hole centered in a fresh drift. Water was pumped to initially fracture the rock and then the acceptance pressure of 850 psi was noted. 4 cubic feet of a chixotropic, fast-setting cement was slow pumped (4 cubic feet per hour) with frequent static holds and a steady but erratic (± 1,000 psi) climb in pumping pressure was noted up to 5,500 psi. Two days later adjacent holes were drilled and fractured with water. The acceptance pressure was 4,500 psi 18 inches from the center, decreased to 1,500 psi 5 feet away and finally reached the ambient rock pressure of 850 psi 13 feet away. This confirmed our ability to over-stress the rock in a local region. We have used this technique to pre-stress the rock just beyond the drift face before each of 5 rounds so that after a round prestressed rock would surround the drift. The packer was set 6 feet in and at the two upper corners of, ""backs"" of the drift and in each case 1 to 2 cubic feet of grout was pumped at the particular rate to achieve variously 5000 to 8,000 psi over pressure presumably in a volume of roughly 5 feet in diameter. Blasting and mucking proceeded within 24 hours. During the past 6 months since this operation was performed caving has been modest in the whole drift whether pre-stressed or not so that a meaningful statistical measure of rock consolidation is not yet available. Several attempts to over-stress rock starting from the ground surface have been attempted."