Before construction of self drilling bolt, designers should firstly survey local geological condition, which mainly includes element, structure, state and character of rock and soil.
As we know, underground water has corrosive effect on buildings, so water-physical property of rock and soil should be made clear to adopt anti-corrosion measures in time and prevent collapse, land subsidence and other damages.
1.Water permeability. It mainly refers to rock and soil’s penetrating quality for underground water. The more cracks in hard rock or karst geology, the stronger water permeability it has. While in loose or soft rock and soil, particulate matter is thin and uneven, so water permeability is poor.
2.Property of softening. It mainly refers to character of mechanical strength reduction after inundating. It mainly exists in clayey soil layer, muddy sand, shale, which is also the index to judge weather resistance and anti-inundating.
3.Destructible property. It refers to soil particle adhesive failure or weakening after moist of rock and soil, which finally causes soil character’s disintegration.
4.Water-supplying property. It mainly refers to that under the effect of gravity, water exudes from cracks or inter space of rock fracture zone.
5.Swell-shrink characteristic. It mainly refers to volume increasing after rock and soil’s water absorption and size decrease after dehydration.