Structure analysis of weathered zone of bedrock slope by seismic prospecting

在风化和侵蚀的平衡作用下，特定的地形与特定的地表物质相关联，其中植被起着重要的作用。坡面植被的破坏往往会带来严重的环境问题，包括径流和产沙，以及水文状况的变化。在此基础上，结合地震勘探资料，对姬路市东部基岩坡面暴露物质的性质进行了研究。折射资料表明，坡面倾角为35 ~ 42度，被纵波速度为800 ~ 1200 m/s的地层所覆盖。在植被覆盖的坡面和基岩坡面，表层通常表现出海市蜃楼现象，这一事实与上述临界流速相结合，可以估计出在植被覆盖的山脊部分，风化物质的最大损失约为10m厚。据估计，从山脊到山谷头部的楔形挤压造成的物质损失的平均深度约为5米，这表明在潮湿气候下，斜坡上植被覆盖的破坏可能产生泥沙。

A particular landform is associated with a definite surface material produced under a balance of weathering to erosion, where a vegetation plays an important role. Destruction of the vegetation covering mountain slope often brings a serious envionmental problem concerning the run-off and sediment yield associated with the change of hydrological situation. From this point of view, the nature of surface materials exposing on bedrock slopes at the east of Himeji City and the Ashio Mountain have been investigated, based on the data by seismic prospecting. The refraction data showed that the slope with the inclination of 35 to 42 degrees have been underlain by the layr with the P-wave velocity of 800-1200 m/sec. The surface layr shows mirage phenomenon commonly on vegetation-covered and bedrock slopes, and this fact together with the critical velocity given above gives the estimation of the maximum loss of weathered material of ca. 10m thick at the ridge part covered with vegetation. The average depth of material loss for a wedge pinching from ridge to vally head is estimated ca. 5m, and this gives the potential of sediment yield by destruction of vegetation cover form slopes under humid climate.