What is the middle sand layer
Classification of strata:Category nameI strongly stable rock;1 hard, integrity, integrity strong, not easy to weathering, Rb>60 MPa;2 layered rock layer, cementation, no weak rock basalt, quartzite, quartz sandstone, limestone and Ordovician Maokou limestoneStability of rock II1, Rb = 40~60 MPa hard;2 layered rock, good cementation;3 hard lump rock, fissure closure without mud filling, Rb>60 MPa conglomerate, sandstone, limestone and other well cementation.III medium stable rock1 medium hard rock, Rb = 20~40 MPa;2 layered rock is hard, with a few soft rock;3 hard rock block, Rb = 40~60 MPa sandstone, sandy mudstone, siltstone and limestone etc..IV weak stable rock1 soft rock, Rb < 20 MPa;2 hard bedded rock;3 Rb = 20~40 MPa lump rock cementation mudstone, sandstone and coal etc. is not good.V Unstable Strata1, high weathering soft rock deliquescence;2 various types of broken rock mudstone, soft limestone, broken sandstone.
Medium sand layer is a kind of artificial foundation layer, the sand grain size is larger than 0.25mm, the sand mass is more than 50% of the total mass.
The middle sand belongs to the Quaternary loose rock, which is a sand layer between fine sand and coarse sand,
