膨胀岩隧道二次衬砌结构受力特性及工程对策分析

Analysis on Mechanical Characteristics and Engineering Countermeasures of Secondary Lining Structure of Tunnel in Expansive Surrounding Rock

膨胀岩对水敏感性强,遇水发生膨胀变形,并产生膨胀压力。为探究膨胀岩隧道在膨胀压力作用下的结构受力特性,以实际隧道项目为工程背景,基于荷载结构法理论,对膨胀岩浅埋隧道在不同的膨胀位置、不同仰拱矢跨比和不同仰拱厚度时的二次衬砌结构的受力特性及变形规律进行了分析和研究。研究结果表明:隧道常规设计断面下,当围岩发生膨胀时,结构承载力不足;当围岩在隧道仰拱和边墙处发生局部膨胀,此工况下的仰拱及拱脚位置处的内力最大,仰拱隆起变形最大,对结构的危害最大;提高仰拱矢跨比和加大仰拱厚度可降低结构内力和抑制仰拱隆起变形,发挥重要作用,但二者提高到一定范围后作用减弱,工程中应视实际情况选择最优仰拱矢跨比和厚度;当围岩在隧道全环发生膨胀时,可通过提高结构混凝土强度等级和配筋率增大结构承载能力。

Expansive rock is highly sensitive to water,expands and deforms when it encounters water,and generates expansion pressure.In order to explore the structural stress characteristics of expansive rock tunnel under the action of expansion pressure,relying on the actual engineering,based on the theory of load structure method,for different expansion positions,the stress characteristics and deformation laws of the secondary lining structure of the shallow buried tunnel of expansive rock with different invert rise-span ratio and invert thickness were studied.The research results show that under the conventional design section of the tunnel,when the surrounding rock expands,the structural bearing capacity is insufficient.When the surrounding rock undergoes local expansion at the inverted arch and side wall of the tunnel,the internal force at the inverted arch and arch foot positions under this working condition is the largest,the inverted arch bulge deformation is the largest,and the damage to the structure is the greatest.Increasing the rise span ratio and increasing the thickness of the inverted arch can play an important role in reducing the internal force of the structure and suppressing the uplift deformation of the inverted arch.However,when the two are increased to a certain range,their effects weaken.In engineering,the optimal rise span ratio and thickness of the inverted arch should be selected based on the actual situation.When the surrounding rock expands in the entire ring of the tunnel,the bearing capacity of the structure can be increased by improving the strength grade and reinforcement ratio of the structural concrete.