外露段与超钻深度对土遗址锚固无损检测影响的室内研究

Influence of the exposed section and over-drilling depth on the nondestructive testing of anchor conservation in earthen sites

为研究土遗址玻璃纤维(GFRP)锚杆锚固系统中外露段长度和锚孔超钻深度对锚固系统基频与采样波形的影响,在室内模拟制作了3根外露段长度为0.5 m,锚固长度1 m,底端预留浆液长度为1 m的试验锚杆系统.试验过程中,首先固定锚固段长度(1 m),对外露段分段切割至0.1 m,然后固定外露段长度(0.1 m)不变,对底端预留浆液部分进行分段切割,以模拟不同的外露段长度与超钻深度.每次切割后,分别采集各外露段长度与各超钻深度下的无损检测波形.通过对采样波形的时域与频域分析,发现随着外露段长度的增加锚固系统基频减小,且外露段长度为0.3~0.5 m时会造成波形失真、干扰信号增加、波形图难以识别,甚至会对锚固质量做出错误评价.对于外露段长度为0.1 m,锚固长度为1 m的土遗址GFRP锚杆锚固系统,超钻深度对锚固系统基频和采样波形的影响均很小.

In order to study the effect of the length of the exposed section and the over-drilling depth of glass fiber reinforced polymer(GFRP)anchor system in earthen sites on the base frequency and sampled waves of the anchor system,three experimental bolts with an exposed length of 0.5 m,anchor length of1 m and reserved grout length of 1 m were made in the laboratory.First,the exposed section was cut into to a final length of 0.1 m at an interval of 0.1 m.Second,the exposed length(0.1 m)was fixed and the reserved grout section at the bottom of the anchor was cut at a law,for simulating different exposed section lengths and different over-drilling depths.After each cutting,non-destructive testing waveforms were taken for the length of each exposed section and the over-drilling depths.By analyzing the time and frequency domain of the sampled waves,it was found that,as the length of the exposed section increased,thebase frequency got smaller.When the length of the exposed section was 0.3-0.5 m,a waveform distortion occurred and the interference signal was strengthened,and the waveform diagram was difficult to identify,and finally the quality of the anchorage would be erroneously evaluated.In addition,the analysis results showed that the impact of the over-drilling depths on the base frequency and sampled waves of the anchoring system was very small for the GFRP anchor system of earthen sites with an exposed section length of 0.1 m and an anchorage length of 1 m.