巨跨扁平洞室施工期拱部沉降分析

为解决巨跨扁平洞室工程现场监测数据匮乏和研究手段单一等现状对洞室变形特征及稳定性分析造成的困扰，以某水平地应力为主应力的巨跨洞室为例，结合洞室的地质条件、地应力及开挖步序，采取现场监测数据分析和三维数值计算的方法，得出巨跨扁平洞室拱部沉降特征。结果表明： 1）巨跨洞室拱部沉降较小，最大值为22.8 mm，且受地质条件、地应力、结构面等因素影响，其变形具有一定的离散性； 2）巨跨洞室中岩柱拆除步序引起的沉降占总沉降的40％~60％； 3）巨跨洞室开挖过程的变形曲线呈现台阶状和锯齿状相结合的特点，其稳定机制为应力控制的整体稳定和结构面控制的局部稳定相结合； 4）巨跨洞室开挖引起的拱顶扰动范围主要存在洞室周边浅层岩体，拱肩附近的扰动范围主要存在洞室周边浅中层岩体，开挖对深层岩体的影响较弱。

Analysis of Arch Settlement Characteristics of Giant-SpanFlat Cavern in Construction Period

Currently, there are problems such as lack of on site monitoring data and single research method in giant span flat caverns, which cause difficulties in analyzing the deformation characteristics and stability of caverns. Here, a case study is conducted on a giant span cavern with horizontal stress as the main stress. Additionally, based on the geological conditions, insitu stress, and excavation sequence of the cavern, the settlement characteristics of a giant span cavern arch are analyzed using on site monitoring data analysis and three dimensional numerical calculations. The results reveal the following: (1) The overall settlement of the giant span cavern is relatively small, with a maximum value of 22.8 mm, it is affected by geological conditions, ground stress, and structure, and its deformation has a certain degree of discreteness. (2) The dismantling sequence of the rock pillar in the giant span cavern accounts for 40%~60% of the total settlement. (3) The deformation curve of the giant span cavern during the excavation process presents the characteristics of a combination of step and zigzag, and its stabilization mechanism is a combination of the overall stability of stress control and the local stability of the structural plane control. (4) The excavation disturbance range of the vault of the giant span cavern mainly exists in the shallow rock mass around the cavern, and the excavation disturbance range near the spandrel mainly exists in the shallow and middle rock mass around the cavern, and the excavation has a weak influence on the deep rock mass.