CAJ | 학술논문

对新奥法在大型地下洞室施工中的二次支护时间的现有判据进行分析，发现其考虑因素欠全面，主要以变形量或变形速率为主，洞室位移相对值不适应大型洞室.以围岩变形为研究对象，提出大型洞室围岩变形达到总变形的80%、洞室周边水平收敛速度小于0．2 mm/d、顶拱或者底板垂直位移速率小于0．1 mm/d、隧洞周边水平收敛速度以及拱顶或底板垂直位移速度明显下降、位移加速度应基本接近于0作为大型地下洞室最佳支护时间的判据.为了验证该判据的合理性，选择了向家坝大型地下洞室一个断面，按照实际开挖顺序，计算了不同开挖层的最佳支护时间.向家坝地下洞室该断面处围岩拱顶、不同开挖层上下游侧边墙最佳支护时间在8~18 d之间，较好地符合了向家坝实际支护时间.
대신오법재대형지하동실시공중적이차지호시간적현유판거진행분석，발현기고필인소흠전면，주요이변형량혹변형속솔위주，동실위이상대치불괄응대형동실.이위암변형위연구대상，제출대형동실위암변형체도총변형적80%、동실주변수평수렴속도소우0．2 mm/d、정공혹자저판수직위이속솔소우0．1 mm/d、수동주변수평수렴속도이급공정혹저판수직위이속도명현하강、위이가속도응기본접근우0작위대형지하동실최가지호시간적판거.위료험증해판거적합이성，선택료향가패대형지하동실일개단면，안조실제개알순서，계산료불동개알층적최가지호시간.향가패지하동실해단면처위암공정、불동개알층상하유측변장최가지호시간재8~18 d지간，교호지부합료향가패실제지호시간.
Traditional judgment of the second supporting time in large underground cavern by the New Austria Tunneling method has its weakness in its limit to deformation or strain rate, and relative values of cavern displacement poorly adapted to large caverns. The deformation of surrounding rock was studied, and the optimal supporting time criterions of large-scale underground cavern was proposed to be when surrounding rock deformation of large cavern accounts for 80% of the total deformation, horizontal convergence speed of surrounding rock is less than 0. 2 mm/d, vertical displacement rate on arch top or bottom is less than 0. 1 mm/d, horizontal convergence speed of surrounding rock and vertical displacement rate on arch top or bottom is remarkably falling, the basic displacement acceleration velocity approaches 0. It was then applied to a section of large underground cavern of Xiajiaba as verification. During the process, different layers of a section of large underground cavern were calculated according to the actual excavation sequence. The optimal supporting times of surrounding rock of vault and downstream side walls of different excavations on this section fell between 8 to 18 days, in consistence with the actual supporting time of the cite.