考虑软岩强度时效弱化的缓冲层让压支护设计研究

Study on design of buffer layer yielding support considering time-effectweakening of soft rock strength

深埋隧道软弱岩体往往具有明显的流变特性和时效弱化效应,隧道开挖后围岩参数随时间的增加逐渐降低,导致围岩流变变形增大,容易造成隧道初期支护和二次衬砌开裂,严重影响隧道施工期及运营期安全。为保证隧道安全,在二次衬砌与围岩之间设置能够吸收围岩流变变形的缓冲层,缓冲层材料具有理想弹塑性特性,其特殊的力学特性使其能够实现与围岩的变形协调,吸收围岩长期变形能,实现软弱隧道围岩的长期稳定。近年来缓冲层让压支护设计逐渐得到众多学者和工程建设单位的认可,但缓冲层让压支护并没有得到广泛应用,原因是让压支护的让压量与让压力的设计一直是工程建设中的难点。基于弹塑性理论,考虑围岩参数的时效弱化和缓冲层支护抗力,提出软岩隧道工程缓冲层让压支护参数的设计方法,并通过V级软岩隧道的支护设计,验证所提缓冲层支护方案的合理性。

The soft rock mass of deep-buried tunnel often has obvious rheological characteristics and time-weakening effect.After excavation,the parameters of surrounding rock gradually decrease with time,resulting in the increase of rheological deformation of surrounding rock,which easily leads to the cracking of first lining and secondary lining of tunnel,and seriously affects the safety of tunnel construction and operation period.In order to ensure safety of the tunnel,a buffer layer is set between secondary lining and surrounding rock,which can absorb rheological deformation of surrounding rock.The buffer layer has ideal elastic-plastic characteristics.Its special mechanical characteristics make it compatible with deformation of surrounding rock,absorbing long-term deformation energy of surrounding rock,and realizing the long-term stability of soft tunnel surrounding rock.Therefore,in recent years,the design of buffer layer yielding support has gradually been recognized by many scholars and engineering construction units,but at present,buffer layer yielding support has not been widely used,because the design of yielding deformation and yielding stress of buffer layer support has always been a difficulty in engineering construction.Based on elastic-plastic theory,the design method of buffer layer yielding support for tunnel engineering is proposed considering the time-effect weakening of surrounding rock parameters and the resistance of buffer layer support.The rationality of the buffer layer yielding support is verified by the support design of V-grade soft rock tunnel.