地质力学磁力模型试验原理及其在工程中的应用

Principle and engineering application of geomechanics magnetic model test

地质力学磁力模型试验借鉴土工离心模型试验中利用离心力模拟重力的思想。在均匀梯度磁场中,掺有铁磁材料的相似材料会受到均匀的磁力作用,由此可以利用均匀的磁力场模拟重力场。根据电磁学基本原理和磁路设计原理,设计并制造了一台2 000匝线圈的均匀梯度磁场发生装置。该装置在220 V电压情况下,能够产生0~16 A电流,在1.2 m×1.2 m×1.0 m试验空间内,可将磁性相似材料的重度提高10~30倍。以锦屏一级电站左岸高陡边坡为例,进行地质力学磁力模型试验。试验结果表明,在一定的电流作用下,可以使模型所受体力的提高倍数达到相似比的要求,并与数值模拟结果进行了对比,试验结果与计算结果基本一致。在增加通电电流时,试验设备可以模拟边坡的超载过程,进而可以求出边坡的超载安全系数。

Geomechanics magnetic model test is inspired by the idea of centrifugal model test, in which the centrifuge force field is used to simulate the gravity field. In uniform gradient magnetic field, material containing ferromagnet is subject to uniform magnetic force. Therefore, gravity can also be simulated by magnetic force. According to the basic principle of electromagnetism, a uniform gradient magnetic field generator is designed and manufactured. There are 2 000-turn coils in the solenoid, whose current ranges from 0 A to 16 A. The magnetic force of ferromagnetic material in the model can be increased 10 to 30 times of the gravity. A geomechanics magnetic model test is carried out using the high slope at left bank of Jinping-I hydropower station as an example. Results of the test are compared with numerical simulation results, which shows that the body force of the model can be increased to the multiple required by the similar ratio under a certain current value. Results of the physical model test are consistent with results of numerical simulation. In addition, if the current continues to rise, the overload process can be simulated, and thus the factor of safety under overload condition can be determined.