物理模型试验光纤传感技术测试方法分析

Analysis of test method for physical model test based on optical fiber sensing technology detection

地下工程常处于复杂三向应力状态,立体模型更能真实反映采场围岩应力状态。将传感光纤分别布置于几何尺寸为3 000 mm×200 mm×1 280 mm平面应力模型和3 600 mm×2 000 mm×2 000 mm立体模型中,分析工作面与光纤不同空间位置时模型应变分布规律。结果表明:传感光纤在模型相似材料铺装前应施加轴向预应力,保持光纤处于预拉状态;温度定位法可实现光纤精准空间定位,当试验环境温度变化明显时,需对传感光纤进行温度补偿以消除温度效应引起的应变测量误差;采动岩体应变分布呈现3个阶段:工作面靠近光纤时,超前支承压力引起下位覆岩应变呈负向台阶变化;工作面过光纤时,垮落、离层区岩层断裂下移引起应变曲线正向台阶变化;工作面远离光纤后,采空区重新压实导致光纤处于受压状态,研究结果对岩土工程类立体模型试验监测具有一定借鉴意义。

Underground engineering is often in the complex three-dimensional stress state,three-dimensional model can actually reflect the stress state of surrounding rock.The sensing fibers are arranged in the plane model with the size of 3 000 mm×200 mm×1 280 mm and the three-dimensional model with the size of 3 600 mm×2 000 mm×2 000 mm,the strain distribution of the model has been analyzed when the working face and the fiber are in different positions.The results show:Sensing fiber should be applied with axial pre-stressing to keep the fiber in pre-tensioned state;Temperature positioning method can achieve fiber spatial positioning;When the temperature changes significantly,the result must be compensated to eliminate the strain measurement error caused by the temperature effect;the strain shift of the optical fiber is in three stages:when the working face is close to the fiber,the strain curve shows a negative step change caused by the lead abutment pressure;when the working face crosses the fiber,the strain curve shows a positive step change because the fracture rock move downward;after the face far away from the fiber,the caving zone re-compaction causes the optical fiber to be under pressure state.