Sentence examples for key strata from inspiring English sources

The effects of grouting are three-folded: (1) to cut off supply to bed-separation water and prevent water logging; (2) to bolster the key strata and alleviate rock pressure incurred by rupture of the key strata; (3) to reduce ground subsidence.

NotesS is limited span of key strata and θ is the break angle of overburden strata.

The limit span of the key strata can be calculated based on the beam model.

Open image in new window Fig. 7 Schematic of panel width design using concept of key strata.

Obviously, in a condition of a narrow panel width, the key strata have a relatively narrow span and do not break.

In effect, bed separations can only grow to the extent bound by the thick-hard strata, which is, therefore, named as the key strata (Qian et al. 1996).

According to the control action of key strata on surface subsidence (Xu et al. 2005), panel width can be designed by stabilizing the most upper key stratum (primary key stratum, KS3) during the extraction (Fig. 7).

If the primary key stratum is not relatively strong and hard, the panel width can be designed based on a lower key stratum (e.g., KS2 in Fig. 7).

If the position of the primary key stratum can be moved upward to exceed 10 times the mining height the possibility of support crushing and water inrush disaster caused by key stratum compound breakage will be lowered.

The panel width (W) can be expressed as: W le S + { 2}D{ tan }theta, (2 where D is the distance from the panel to the key stratum, θ is the break angle of the rock strata.

Published researches (Qian et al. 2010) indicated that there exists single key stratum structure, the lithology is hard partial to hard, which determined the particularity of the roof bedrock movement of the SLW face.