新建隧道建设中下穿既有高速公路施工的力学探讨

Mechanical Discussion on Construction of the Existing Expressway in Construction of New Tunnel

基于河北某下穿高速公路的新建隧道工程,对其在施工过程中的受力及围岩稳定性进行了研究,通过围岩参数、围岩、覆盖层厚度、施工方法的二维和三维有限元计算。结果表明,各种计算工况表明支护结构和围岩稳定,能满足结构受力和围岩稳定的要求;采用三台阶法能能达到结构受力和围岩稳定的要求。随着开挖的不断增加,结构水平位移和竖向位移均随之增加,开挖时各台阶均有急骤增加趋势。围岩最小主应力和最大主应力随埋深的增大而上升,但是影响程度不大;初期支护最小和最大主应力均随埋深的增大而显著增大,围岩塑性区范围也随之增大,在埋深大于305 m后趋于稳定。通过现场监控量测,在施工过程中,对支护结构工作状态及时掌握,确保隧道施工质量及安全,现场监测表明隧道结构安全稳定。

Based on a newly built tunnel under a highway in Hebei,the stress and surrounding rock stability during construction are studied. Two dimensional and three dimensional finite element calculation of surrounding rock parameters,surrounding rock,overburden thickness and construction method is carried out. The results show that all kinds of calculation conditions indicate that the supporting structure and surrounding rock are stable,which can meet the requirements of structural stress and surrounding rock stability. The three step method can meet the requirements of structural stress and surrounding rock stability. With the increase of excavation,horizontal displacement and vertical displacement of the structure are increased when the step excavation has increasing trend. With the increase of burial depth,the minimum and maximum principal stresses of the surrounding rock increase slightly,and the burying depth has little influence on them. With the increase of burial depth,the minimum and maximum principal stresses of the initial support increase obviously,and the plastic zone area of the surrounding rock also increases. After the burial depth is greater than 305 m, the surrounding rock tends to be stable. Through on-site monitoring and measurement,in the process of construction,we can grasp the working status of supporting structure in time and ensure the quality and safety of tunnel construction. Field monitoring shows that the tunnel structure is safe and stable.