钢骨混凝土井壁水平极限承载特性的试验研究

Horizontal Ultimate Bearing Capacity of Encased Steel Concrete Shaft Lining

针对600～800 m巨厚冲积层中煤矿立井井筒的支护问题,提出了采用钢骨钢纤维高强混凝土井壁结构型式.为了研究该种井壁结构的水平极限承载特性,根据相似理论,采用物理模拟试验的方法,开展了2个模型井壁的破坏性试验,研究了该种井壁结构的水平极限承载特性和变形破坏特征.试验研究表明:在竖向荷载(井壁自重应力)加载阶段,钢骨和混凝土能够协同变形;水平荷载加载阶段,钢骨应变达到屈服应变后,钢骨表现出一定的塑性流动变形能力;井壁破坏时,钢骨和混凝土的切向应变值可达-3500×10-6(压);利用厚壁圆筒的弹性、塑性极限承载力估算井壁的水平极限承载力上、下限值,试验值更接近塑性极限承载力;由于钢骨和钢纤维的加入使得高强混凝土的脆性得到改善,钢骨钢纤维高强混凝土井壁具有更好的塑性变形能力和延性,是深厚表土层中一种可行的井壁结构型式.

Aiming at the support problems of the shaft lining in extra thick alluvium ranging from 600 m to 800 m in depth,we propose the method of using the encased steel and steel fiber reinforced high strength concrete shaft lining.To study its horizontal ultimate bearing and deformation characteristics,two shaft lining model destructive tests were performed with the physical simulation testing method based on the similarity theory.The results show that the deformation of encased steel can have a cooperation deformation with the concrete during the vertical loading（shaft lining self-weight stress） stage.The encased steel has a certain plastic flow deformation capacity when its strain reaches the yield value during horizontal loading stage.And the shear strain values of the encased steel and concrete can reach-3500×10-6（pressure） when the shaft lining is damaged.In addition,compared with the upper and lower limit values of horizontal ultimate bearing capacity estimated by the elastic and plastic ultimate bearing capacity of the thick cylinder,we find that the experimental values are very close to the plastic ones.The encased steel and steel fiber reinforced high strength concrete shaft lining has been improved in both brittleness and highe horizontal ultimate bearing capacity.Therefore,it is feasible for deep alluvium.