Formation Mechanism of “Large-Area Sweating” Water Seepage from Deep Mine Sandstone Pores

Table 5

Hydrogeological features of three layers of sandstone aquifers.

Aquifer features	Jurassic sandstone	Shihezi sandstone	Shanxi sandstone
Grain size	Medium, fine, and coarse sandstone and conglomerate	Medium and fine sandstone and a small amount of coarse sandstone	Medium and fine sandstone and a small amount of coarse sandstone
Thickness (m)	Single layer of 2.50-35.40; total thickness of 176.20-460.65	Single layer of 2.70-30.25; total thickness of 34.50-270.80	Single layer of 4.10-20.30; total thickness of 4.10-52.80
Types of groundwater	Confined pore water and fracture water	Confined pore water and fracture water	Confined pore water and fracture water
Pore permeability	Medium-low	Low-ultralow	Low-ultralow
Fracture numbers	A small amount, developed locally near faults and folds	A small amount, developed locally near faults and folds	A small amount, developed locally near faults and folds
Main hydrochemical types	HCO3^-·SO4^2--Na^+	SO4^2--Na^+	HCO3^-·SO4^2--Na^+
Reservoir pressures (MPa)	3.16-14.69	5.08-17.74	6.55-19.21
Unit water inflow (L/s m)	0.0471-0.1550	0.0039-0.0400	0.0020-0.0415
Water abundance	Weak-moderate	Weak	Weak