压力隧洞混凝土衬砌再裂判断的钢筋混凝土曲梁法

Assessment of the second cracking occurrence of pressure tunnel concrete linings

说明了利用钢筋混凝土曲梁理论判别混凝土衬砌是否发生第二次开裂的原理和方法,讨论了基本参数如围岩切向抗力τ、法向抗力σr(ra)+pa、钢筋应力不均匀系数ψ的估值范围。通过算例分析了衬砌外缘渗压pa,围岩切向抗力τ,钢筋最大应力σ's,钢筋应力不均匀系数ψ,衬砌围岩的接触状态等重要因素对再裂的影响。分析表明,对于透水衬砌在衬砌脱开围岩独立工作的一般情况下,不易发生第二次开裂。

After the first series of cracks of tunnel reinforced concrete linings has formed,to calculate the crack width we must know whether or not an increasing internal water pressure can cause a second series of cracks of these linings.This paper discusses the principle and method for assessment of the second cracking and the possible range of basic parameters,such as average shear-friction stress τ,sum σr（ra）＋pa of the normal contact stress（between lining and surrounding rock mass） and pore pressure paon the outer side of the concrete linings,and ratio ψ=s σ′ s of average stress s over the maximum stress σ′ s of reinforcement.An example is used to analyze the effects of these parameters and the contact state between lining and rock mass on the second cracking.The conclusion is that the second series of cracks does not occur when crack reinforced concrete linings work independently.