Given the analysis of underground pressure, a stress calculation model of coal floor stress has been established based on a theory of elasticity. The model presents the law of stress distribution on the relatively fix...Given the analysis of underground pressure, a stress calculation model of coal floor stress has been established based on a theory of elasticity. The model presents the law of stress distribution on the relatively fixed position of the mining coal floor： the extent of stress variation in a fixed floor position decreases gradually along with depth, the decreasing rate of the vertical stress is clearly larger than that of the horizontal stress at a specific depth. The direction of the maximum principal stress changes gradually from a vertical direction to a horizontal direction with the advance of the working face. The deformation and permeability of the rock mass of the coal floor are obtained by contrasting the difference of the principal stress established from theoretical calculations with curves of stress-strain and permeability-strain from tests, which is an important mechanical basis for preventing water inrush from confined aauifers.展开更多
A new composite two component grout comprised of modified urea-formaldehyde resin and cement was formulated to take account of the advantages and disadvantages of both the cement grout and the chem- ical grout. The ne...A new composite two component grout comprised of modified urea-formaldehyde resin and cement was formulated to take account of the advantages and disadvantages of both the cement grout and the chem- ical grout. The new grout is designed for water blocking by reinforcing as well as seepage control by bore grouting. The A component consists of a modified urea-formaldehyde resin A component, some cement, and some water. The B component is an alkaline coagulant. An orthogonal test of four factors at three lev- els showed that gel time increased with increased water content and with urea-formaldehyde resin con- tent. Gel time decreased at increased levels of alkaline coagulant. The A component of this new composite grout is stable over time. A mixed cross-over test showed that as the volume ratio of A to B increases the gel time falls at first but then increases. The solid strength decreases with increasing levels of the B com- ponent. The solid strength increases over time and becomes stable by the 28th day after mixing. The vis- cosity increases with increasing levels of resin A component. The increase is exponential and may be fit to： μ = 8.162e0.0286x.展开更多
文摘Given the analysis of underground pressure, a stress calculation model of coal floor stress has been established based on a theory of elasticity. The model presents the law of stress distribution on the relatively fixed position of the mining coal floor： the extent of stress variation in a fixed floor position decreases gradually along with depth, the decreasing rate of the vertical stress is clearly larger than that of the horizontal stress at a specific depth. The direction of the maximum principal stress changes gradually from a vertical direction to a horizontal direction with the advance of the working face. The deformation and permeability of the rock mass of the coal floor are obtained by contrasting the difference of the principal stress established from theoretical calculations with curves of stress-strain and permeability-strain from tests, which is an important mechanical basis for preventing water inrush from confined aauifers.
基金the Graduate Developing Innovation Project of Jiangsu Province of China (No. CXZZ11-0306)the Major State Basic Research and Development Program of China (No.2007CB209400)
文摘A new composite two component grout comprised of modified urea-formaldehyde resin and cement was formulated to take account of the advantages and disadvantages of both the cement grout and the chem- ical grout. The new grout is designed for water blocking by reinforcing as well as seepage control by bore grouting. The A component consists of a modified urea-formaldehyde resin A component, some cement, and some water. The B component is an alkaline coagulant. An orthogonal test of four factors at three lev- els showed that gel time increased with increased water content and with urea-formaldehyde resin con- tent. Gel time decreased at increased levels of alkaline coagulant. The A component of this new composite grout is stable over time. A mixed cross-over test showed that as the volume ratio of A to B increases the gel time falls at first but then increases. The solid strength decreases with increasing levels of the B com- ponent. The solid strength increases over time and becomes stable by the 28th day after mixing. The vis- cosity increases with increasing levels of resin A component. The increase is exponential and may be fit to： μ = 8.162e0.0286x.
