Journal of Coal Science and Engineering (China)

Permeation grouting is widely applied for its low grouting pressure and minor disturbance to the stratum in grouting engineering, especially in engineering with strict requirements on ground settlement. However, permeation grouting theory lags behind compared with other engineering disciplines, and the theoretical formulas now available cannot accurately be used to guide grouting engineering design and predict the cost and effects of grouting due to many factors affecting grout permeation in stratum. In this study, permeation grouting experiment devices were independently manufactured with the characteristics of easily controlling grouting pressure, simulating sandy strata grout, and detecting grouting effect. Using a uniform design, the sand consolidation agent, as grouting material, its spread in Shenyang sandy strata was tested with these experiment devices. The quantitative relations between grouting factors (grouting pressure, strata parameters, water-sand consolidation agent ratio) and grouting effects (grout spread radius, gell strength, grout amount) are obtained with regression analysis, and the influence degree of grouting factors on grouting effects is studied.

The strata of Jurassic was divided into three tectonic sequences and eight sequences of third rank, according to the developing feature of the tectonic inconformity and the transforming feature of the depositional system tracts. Also the identification and the division of the base-level cycle of different period were carried through. Therefore three cycles of super period, eight cycles of long period, twenty-four cycles of middle period and some cycles of short period were identified. From the overall character of the coal-accumulation in the Mesozoic, we can see that the Yan’an formation is of the best nature of coal bearing. When the coal bearing systems of Jurassic were depositing, the Ordos area is the coal accumulating basin of terrene of large scale and located in the same tectonic unit. But the local structure of different part and the paleolandform are different in the basin, which resulted in the difference of the depositional environment. So the layer number and the distribution of the thickness of the coal beds are different in the different part of the basin. The coal-accumulating action migrated regularly along with the development, evolvement and migration of the depositional systems. The layer numbers of the coal beds, which can be mined, are more in the north and west fringe of the basin, whose distributing area is extensive, and they are more steady in the landscape orientation, also the total thickness is great. Therefore the nature of coal bearing and the coal-accumulating action of different part changed obviously in the space in Ordos area.

To investigate the water-inrush process due to floor heave, simulation model was made and factors of mining height, immediate roof strength, water pressure, depth and strength of confiningbed, excavation step distance and bury depth were analyzed by using UDEC software. Five zones theory (containing two maximum main stress circles and three maximum main stress stratiform zones) along excavation direction was proposed, and two-ends-fixed beam mechanical model in maximum main stress circle was established. It is found that water inrush always occurs at the end of the beam where shear stress is higher, that is to say, it always occurs at near the starting cut and working face. Water pressure, height and strength of confiningbed are the determined factors, and mining height, immediate roof strength, excavation step distance and bury depth effect water inrush process due to floor heave.