【摘要】 探地雷达用于多年冻土区的勘测一般通过钻孔和探坑进行直接对比来确定冻土层分布状况,但在野外工作中,钻孔资料一般很难得到,而探坑在有限的人力物力条件下也很难开挖,这给冻土层的野外确定带来很大困难.我们采用雷达探测资料寻找浅层地下冰深度来确定多年冻土上限的深度,企图能在没有现场对比资料的情况下寻找一种利用探地雷达探测多年冻土的简易方法.探测结果显示,通过地貌特征寻找浅层地下冰可能存在的典型地段进行雷达探测能很容易确定多年冻土上限的位置.2007年在祁连山区利用Pulse EKKO Pro探地雷达进行了多年冻土的野外探测,结果显示:大雪山老虎沟海拔3 684 m(39.5907°N;96.4339°E)处多年冻土上限约为2.2 m,在冷龙岭北坡的水管河源头海拔4 053 m(37.5463°N;101.7709°E)至海拔3 907 m(37.5508°N;101.7752°E)处的多年冻土上限深度为2.5 m,在宁昌河源头沿河岸从海拔3 448 m(37.5649°N;101.8455°E)至海拔3 377 m(37.5797°N,101.8377°E)处多年冻土上限为2.4 m,在走廊南山的观山河源头海拔3 468 m(39.2615°N;98.6715°E)处多年冻土上限深度在2 m左右.另外根据4个勘察区多年冻土特征地貌分布区的最低分布海拔总结得出,老虎沟地区为冻土下界分布最高地区,关山河源头为冻土下界分布最低地区.其原因主要是降水和植被的差异造成的结果,降水量大和植被良好的地区多年冻土下界的分布海拔就低,反之亦然.更多还原

【Abstract】 In 2007,a ground-penetrating radar(GPR) sounding was performed to study the permafrost in the Qilian Mts.In Laohugou of Daxue Range,a 30 m long GPR sounding profile was obtained on road at 3 684 m a.s.l.(39.5907° N;96.4339° E),which showed that the permafrost table was at 2.2 m depth and there was a layer of 80 cm ground ice just under the table.The lower limit of permafrost was at 3 600 m a.s.l.hereabout.The Shuiguan River profile from 4 053 m a.s.l.(37.5463° N;101.7709° E)to 3 907 m a.s.l.(37.5508° N;101.7752° E) showed that the permafrost table was 2.5 m deep and there was a layer of some 2 m ground ice in a mesa-butte of Neoglaciation sediments.From the distribution of sorted polygon,frost mound and thermokarst,one can concluded that the lower limit of permafrost was at 3 500 m～3 600 m a.s.l.In Ningchang River basin,from 3 448 m a.s.l.(37.5649° N;101.8455° E)to 3 377 m a.s.l.(37.5797° N,101.8377° E),obviously permafrost table could be seen at the depth of 2.4 m in frost mound island section,and lower limit of permafrost could be seen at 3 400 m a.s.l.In Guanshan River basin and the South Zoulang Range,where the GPR profile was from 3 468 m a.s.l.(39.2615° N;98.6715° E)to 3 469 m a.s.l.(39.2598° N;98.6711° E),permafrost table was at the depth of 2 m,and there was ground ice,2～3 m in thickness,under the lake beach at 3 469 m a.s.l.According to the geological profiles at 3 309 m a.s.l.and 3 311 m a.s.l.,it was inferred that the permafrost is probably between 3 300～3 400 m a.s.l.Finally,it was concluded that the highest lower limit of permafrost was in Laohugou region,and the lowest lower limit of permafrost was in Guanshan River region.The main reason that cause such a permafrost distribution is the differences of precipitation and vegetation from west to east of the Qilian Mts.In regions where there are more precipitation and better vegetation the lower limit of permafrost is higher,and vice versa.In addition,from the studied results,it is found that the permafrost table depth have no obvious difference,all about 2～2.5 m.更多还原