光纤光栅传感监测在拱坝地质力学模型试验中的应用

Application of Fiber Bragg Grating Sensor in Geomechanical Model Test of Arch Dam

光纤光栅传感在土木工程原型监测中逐步得到广泛应用,然而在水工地质力学模型试验中应用较少。以木里河立洲拱坝地质力学模型为基础,在坝顶及上游坝面布置光纤光栅传感器,对坝体在超载过程中的应变进行监测,通过光纤光栅传感器监测得到的应变及变化曲线,分析了地质力学模型拱坝坝面的开裂破坏过程。成果表明:Kp=1.0时,坝体工作正常;Kp=1.2～2.2时,坝踵处出现初裂;Kp=2.2～3.0时,曲线有转折和拐点的出现,左岸坝肩岩体受内部结构面影响发生较大的位移;Kp=3.6～4.3时,坝体应变整体出现较大的波动,其中左拱端应变曲线C17测点出现较大拐点,左拱发生开裂;此后,应变曲线陆续出现波动或转向,坝体裂缝不断发展,直至逐渐失去承载能力。通过与常规的应变片检测方法进行对比分析,验证了光纤光栅传感器在地质力学模型试验中应用的可行性。

Fiber bragg grating（FBG） sensor monitor has been widely applied in civil engineering,yet it is less used in hydraulic geomechanical model test.Based on the geomechanical model of Lizhou arch dam on Muli River,we arranged FBG sensors on the crest and upstream surface of the dam to monitor the dam strain in the process of overload.Through the strains and variation curves obtained by FBG,we analyzed the cracking propagation on the arch dam surface.Results showed that when Kp=1.0,the dam was in normal condition;when Kp=1.2-2.2,initial cracks appeared at the dam heel;when Kp=2.2-3.0,inflexion points of the strain curve occurred,which revealed large displacement of the rock mass in the left bank abutment;when Kp=3.6-4.3,the strain curve fluctuated sharply on the whole,with cracks on the left arch;subsequently,the strain curve fluctuated successively,indicating that the cracks on the dam developed steadily until failure happened.Comparison with the results from strain gauge verified the feasibility of applying FBG to geomechanical model test.