公路隧道型钢喷射混凝土初期支护安全评价研究

Study of initial support safety evaluation about shape steel reinforced shotcrete in highway tunnel

公路隧道常采用复合式衬砌,按"新奥法"原理进行设计和施工。对于软弱围岩段,采用型钢拱架(或格栅拱架)+注浆+锚喷网联合初期支护形式,型钢喷射混凝土初期支护的安全性评价方法是实现支护动态设计的关键。对初期支护安全性评价进行系统研究,建立了型钢喷射混凝土安全性评价数值计算方法。首先,根据监测数据分析围岩最终沉降量、水平收敛值,作为围岩力学参数反演的依据;其次,采用反演的力学参数,通过地层-结构法数值计算型钢拱架喷射混凝土初期支护内力;最后,采用型钢混凝土安全系数计算方法计算和评价初期支护安全性。研究发现,型钢拱架喷射混凝土初期支护能发挥型钢强支护作用,而喷射混凝土达到设计强度后,混凝土起主要支撑作用,型钢间距对提高初期支护安全系数不显著。

Composite linings are often adopted in highway tunnels. The new Austrian tunneling method is used in tunnel＇s designing and construction. For weak wall rock section, steel arch（or grid arch） ＋ grouting ＋ shortcrete network of united initial support form are adopted. The key to achieve dynamic design is to find a good method to evaluate initial support safety evaluation about shape steel reinforced shotcrete. This paper gives a systemic study on initial support safety evaluation and established a numerical calculation method. Firstly, according to the monitoring data, this paper analyzes the final settlement value and horizontal constringency of wall rock and makes it as a basis for parameter inversion. Secondly, adopting the mechanical parameters from inversion, the initial support internal force about shape steel reinforced shotcrete is calculated by stratum-structure numerical method. Finally, initial support safety is calculated and evaluated by safety factor calculation method of shape steel reinforced shotcrete. From the study of this paper, we find that the initial support of shape steel reinforced shotcrete can exert the strong support effect of shape steel. And that, when the shotcrete is upgraded, concrete plays a major supporting role. The space between shape steels is not prominence in increasing the initial support safety factor.