箍筋对深基坑支撑梁爆破拆除的影响机制

Influence Mechanism of Stirrup on Blasting Demolition of Support Beams in Deep Foundation Pit

深入解析箍筋对钢筋混凝土支撑梁爆破拆除时侧向作用机制是合理选用支撑梁预处理方法的关键。基于箍筋对混凝土梁侧向约束效应理论分析,研究其对支撑梁爆破拆除时核心区混凝土单元应力状态影响机制,确定箍筋最优剪断位置;并结合支撑梁爆破拆除数值模拟与工程实践,对比分析箍筋侧向约束解除前后截面单元峰值应力分布规律、梁身破碎区形态及爆破拆除效果。结果表明:箍筋侧向约束解除后,核心区大量混凝土单元由三向受压变为单向受压,抵抗变形破坏的能力降低;箍筋所在截面处混凝土单元峰值拉应力整体取值向大值过渡,单元主要以受拉失效破坏为主;选取支撑梁侧面靠下位置切断箍筋,可显著改善支撑梁爆破拆除效果,有效防止爆破飞石危害。

In depth analysis on the mechanism of the lateral constraint effect of stirrups on blasting demolition of reinforced concrete support beams is the key to select reasonable pretreatment method of the support beam. The influence mechanism of the concrete element stress state in the core area of the support beam during blasting demolition is studied based on theoretical analysis of lateral restraint effect of stirrups on concrete beams,and the optimal cutting position of stirrup is determined. Combined with the numerical simulation and engineering practice of blasting demolition of support beam,the distribution law of the peak stress of the section element,the shape of the broken zone and the blasting demolition effect of support beam are comparatively analyzed before and after lateral constraint effect is released. The results show that,a large number of concrete elements in the core area change from three-dimensional compression to uni-dimensional compression,and the ability of concrete element to resist deformation and failure is gradually reduced after the lateral constraint effect of stirrups is released. The overall value of the peak tensile stress of the concrete element is transferred to the large value at the cross section of the stirrup,and this element is mainly subjected to tensile failure,and the cutting of stirrup on the side of the supporting beam can significantly improve the blasting demolition effect of the supporting beam and effectively prevent the damage of the blasting flying rock.