拱坝坝肩稳定地质力学模型试验及孔口概化影响分析

Stability Analysis of Arch Dam Abutment by Geomechanics Model Test and Impact Study on Orifice Generalized Simulation

在拱坝坝肩稳定地质力学模型试验中,坝身的泄洪孔口经缩尺后尺寸偏小,模拟困难,通常需概化模拟,以方便模型的加工制作和加载,但孔口概化对试验结果的影响需深入研究。为此,以立洲拱坝工程为例,分别开展了孔口概化后的坝肩稳定地质力学模型试验、坝身开孔与不开孔的两个三维有限元模型模拟分析,并对比分析三种方案所获得的应力分布特征、位移分布规律、塑性区分布范围和稳定安全度,探讨了孔口概化对地质力学模型试验结果的影响。结果表明,有限元开孔方案与不开孔方案坝体应力相差不超过10%,坝体位移相差不超过12%,塑性区发展过程基本一致,开孔方案的起裂、塑性区贯通和失稳略早于不开孔方案;有限元不开孔方案极限超载安全系数较地质力学模型试验方案大0.65%,有限元不开孔方案极限超载安全系数较开孔方案小15.48%。原因系拱坝坝身开孔导致拱效应降低,梁效应增强,但对坝体的位移、应力、塑性区分布影响较小。因此在研究拱坝坝肩稳定性的地质力学模型试验中,其采取的坝身孔口概化模拟方法对试验结果影响不大。

In the geomechanical model test of arch dam abutment stability, the size of flood discharge outlet on the dam is too small to be simulated when they are scale down. In order to facilitate the manufacture and load force, it usually needs to be generalized simulation. However, the impact of the generalized orifice on the test results needs to be further studied. This paper takes the Lizhou arch dam project as an example to carry out a geomechanical model test without outlets,and two 3D finite element models test with and without outlets on the dam. The displacement, stress, plastic deformation and safety factor obtained by the above three schemes are compared. And then the impact of generalized outlet on geomechanical model test results is discussed. The results show that the stress difference between the 3D finite element models test with and without outlets on the dam does not exceed 10%, the displacement difference between the dam body does not exceed 12%;The development process of the plastic deformation is basically the same, and the cracking, plastically deformation zone penetration and instability of the scheme with outlets on the dam is earlier than the scheme without outlets on the dam;The ultimate overloading safety factor of the scheme without outlets on the dam is 0.65% larger than that of the geomechanical model test scheme;The ultimate overloading safety factor of the scheme without outlets on the dam is 15. 48% smaller than that of the scheme with outlets on the dam. It can be inferred that the outlets of the dam body will lead to the reduction of the arch action and the enhancement of the beam effect, but it has little impact on the displacement, stress, and plastic zone distribution of the dam body. Therefore, for the research of geomechanical model tests for the stability of the arch dam abutment, the orifice generalized simulation of arch dam has little impact on geomechanical model test.