钻井井壁破坏原因分析及防治

Analysis of the Causes of Partial Shaft Drilling wall Damage and Preventives against damage

介绍谢桥东二风井钻井井壁在马头门处的破坏情况,分析破坏原因,提出防治意见。

№2 ventilating shaft, with depth of 479.2m, net diameter of 7.5m, overburden thickness of 421m and basement rock thickness of 58.2m, is constructed by shaft drilling and prefabrication shaft wall components. It was discovered in June, 1991 that north shaft wall of shaft ingate, 1.7—2.6m above floor, damaged.the damage of north shaft wall includes shaft wall falling away in pieces.some lm length of reinforced steel bars laying bare.There were two crackes with width of 8—10mm in connection.Concrete of 0.8m^2 at east ingate also fell away and reinforced steel bars explosed. What are the causes of shaft wall damage? The author recognizes that causes of shaft wall damage are too small shaft wall encircling force and too low shaft wall strength instead of vertical minus friction force. Strengthing shaft is to adopt principle of specific gravity difference, one use cement slurry to displace soil slurry of outside shaft wall.shaft was strengthed after 30 days of finishing shaft drilling.When strengthing shaft, soil slurry of outside shaft wall precipitated and specific gravity of soil slurry is getting heavy so that cement slurry is not able to displace all the soil slurry out, strength of solidified cement slurry is too low, leading to much small encircling force. surrounding rock stress near shaft achieves 16—25 MPa to make shaft supporting difficult.Preventives are to strengthen ingate and adopt single ingate; to increase shaft wall strength and rigidity of new designing shaft; to put a layer of asphalt between shaft outside wall and surrounding rock; to improve shaft wall strengthing technique to make soil slurry displace upon fully.