地下厂房布置优化及施工过程的显式有限差分法数值模拟

NUMERICAL SIMULATIONS OF LAYOUT OPTIMIZATION AND CONSTRUCTION PROCESS OF UNDERGROUND POWERHOUSE WITH EXPLICIT FINITE DIFFERENCE METHOD

在支护条件下模拟岩土工程的施工过程时,无论在二维还是三维数值计算方面,显式有限差分法连续介质快速Lagrange分析程序FLAC2D和FLAC3D具有明显优势。以雅砻江官地水电站地下厂房洞室群为研究对象,结合水电站地下厂房的主厂房、主变室和尾水调压室3大洞室平行布置的特点,并考虑模拟效率和计算成本,首先采用FLAC2D进行地下厂房3大洞室各种布局和间距方案的分析比较和优化,得到安全经济的方案;再利用FLAC3D对确定方案下厂房洞室群在支护条件下的施工过程进行三维模拟分析,计算得到在开挖过程中洞室围岩的变形、应力、塑性区分布以及支护结构的受力特征。这种综合利用FLAC2D和FLAC3D,对地下厂房布置优化和施工过程分别进行二维和三维显式有限差分数值模拟的计算方案合理可行,所得结果和规律可用于指导地下厂房的设计和施工。

Numerical simulation is one of the main approaches to deal with such problems as reasonable layout and construction of underground powerhouse. The computer codes for fast Lagrangian analysis of continua, FLAC and FLAC^3D, with the explicit finite difference method are regarded to be suitable respectively for both two- and three-dimensional numerical simulations of problems involving supported construction process in geotechnical engineering. As an engineering example, the cavern group of the underground powerhouse of Guandi Hydropower Station on the Yalong River in Southwest China is analyzed. The two-dimensional FLAC analysis is performed firstly for the optimization of location and spacing schemes of the three main chambers, i.e. the generator chamber, the main transformer chamber and the tail water surge chamber, considering their parallel arrangement and the modeling efficiency and computing cost. Then, the entirely-supported construction process of the cavern group of the underground powerhouse under the determined optimal layout scheme is simulated in three dimensions with FLAC3~. The distributions of displacement, stress and plastic deformation in the rock masses surrounding the caverns and the loads carried by the supporting structures are obtained. It is proven by the results that the numerical simulations of the layout and construction process of underground powerhouse with explicit finite difference method using respectively FLAC^2D and FLAC^3D match those of the practical case. The results from nonlinear stress analyses can be used to guide the design of excavations and rock supporting mechanisms.