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结合波纹膜片的压力敏感特性和光纤Bragg光栅(FBG)的应变传感特性,设计了一种新型的FBG渗压传感器。传感器通过拉杆式结构将波纹膜片在应力下的挠度变形转化为FBG的轴向应变,通过恒温条件下的压强标定试验,得出传感器的压强灵敏度约为20 nm/MPa,和普通光栅相比,其压强灵敏度提高了6 000多倍。对传感器探头内部的光栅进行了温度特性标定试验,通过温度补偿光栅消除外界温度对渗压测量结果的影响。将该传感器用于隧道涌水模型的开挖试验,测得模型注水过程中测点的渗压值不断增大并趋于稳定,隧道开挖过程中渗压值轻微波动,提升水位时渗压值急剧增大。
A new type of FBG piezosensor was designed based on the pressure sensitive properties of the corrugated diaphragm and the strain sensing characteristics of the fiber Bragg grating (FBG). The sensor converts the deflection of the corrugated diaphragm under stress into the axial strain of the FBG through the rod structure. The pressure sensitivity test of the sensor under constant temperature shows that the pressure sensitivity of the sensor is about 20 nm / MPa. Compared with the ordinary grating , The pressure sensitivity increased 6000 times. The grating inside the sensor probe has been calibrated for temperature characteristics, and the effect of outside temperature on the measurement of seepage pressure is eliminated by temperature compensation grating. The sensor was used in excavation test of tunnel gushing water model. The seepage pressure value of measuring point during the process of water flooding was increased and stabilized. The seepage pressure value fluctuated slightly during tunnel excavation, and the seepage pressure Sharply increased.