西部软岩地层基于内外壁联合承载的冻结井壁减薄方法

Method for reducing freezing shaft wall thickness based on the combination of inner and outer walls in soft rock strata of western China

为解决深部软岩地层冻结井筒内壁设计厚度较大问题,运用煤矿立井井筒设计理论和锚杆支护理论,研究了冻结井筒内层井壁、外层井壁和围岩的联合承载受力机理,提出了一种新型井壁结构形式和内层、外层井壁厚度减薄方法,即在井壁围岩中打入短锚杆,锚杆端头浇筑在外壁内部,并将锚杆端头闭锁的钢丝绳连接在内壁钢筋上,通过不同结构联合承载的方式提高内壁和外壁的承载能力,进而减薄井壁厚度。以内蒙古红庆河煤矿副井-640~-660 m冻结段为研究对象,通过理论计算得出了采用新型井壁结构形式后的井壁厚度,其中新型内层井壁厚度较原井壁可减薄12.5%,外层井壁厚度可减薄20%;结合数值模拟手段,给出了新型井壁中的应力传递过程。数值计算表明:新型内层井壁内缘混凝土的压应力值为24.5 MPa,小于原内层井壁内缘混凝土压应力值,验证了新型井壁结构的安全性和可靠性;新型井壁结构中,锚杆和钢丝绳传递的外力主要由外壁的刚性变形承担,锚杆在软岩地层中提供的锚拉作用很小,工程应用时可以缩短锚杆的钻入长度,避免锚杆钻入过程中打穿偏斜的冻结管。这种新型井壁结构将外层井壁强度通过钢丝绳和锚杆连接纳入到了内层井壁的承载体系中,提高了内层井壁的承载力,减薄了井壁厚度。

To optimize the inner wall thickness of frozen shaft wall in a deep soft water-rich layer,the combined bearing mechanism of the inner wall,outer wall and surrounding rock is investigated by using the shaft design and bolt support theories.A new type shaft wall structure and a thickness reduction method of inner and outer walls are put forward,in which short bolts are drilled into the surrounding rock.The ends of the bolts are embedded in the outer wall and the wire ropes which fixed at the end of the bolts are combined to the reinforcing bars of the inner wall.The bearing capacity of the inner and outer walls is improved and the thickness of the shaft wall is reduced due to the combination of the structures.Furthermore,the stress transfer process in the new shaft wall is given by means of numerical simulation.Specifically,in this paper,the-640--660 m frozen section of the auxiliary shaft in Hongqinghe coal mine is taken as a research object,and the corresponding thicknesses are obtained.That is,the thickness of inner wall is reduced by 12.5%,and its outer wall is reduced by 20%when the new shaft wall structure is adopted.The numerical calculation shows that,in the new inner layer shaft wall,the compressive stress value of the inner edge concrete is 24.5 MPa,which is lower than that of the original one.Therefore it verifies the safety and reliability of the new shaft lining structure.In the new shaft lining structure,the external forces transmitted by the anchors and wire ropes are mainly resisted by the outer wall,and the axis forces of bolts in soft rock strata are small.Hence,the drilling length of bolts can be shorted in actual engineering cases to avoid frozen pipes damaged during the bolts drilling processes.On the other hand,the strength of the outer wall is re-integrated into the bearing system of the inner wall through the connection of wire ropes and bolts,which improves the bearing capacity and effectively reduces the thickness of the shaft lining.