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大湖岸线后退,美国沿潮一带的州以及加拿大部分省份的财产损失达数百万美元。已投资开展了许多科研项目研究冲刷问题。研究的结果表明,陡岸下部受波浪作用是岸线后退的主要原因,本文所研究的是造成陡岸坍塌的各种物理因素,其中之一是地下水对陡岸稳定性的作用。密执安湖沿岸某些地段的崖顶每年后退9至10米,据记载这种后退与底部冲刷无关。后来使用了25个测压计测量地下水头,搞清了这些地段的复杂的地下水系统。发现在承压水头以下陡岸底部之上5米处是冰积沙层。在岸顶的滑动断裂冰碛层中,发现另一个“滞水”系统。根据一年多地下水位变动的记录,测到在下伏沙层中水位变动达13米。地下水位的变动对陡岸的稳定影响极大。在边坡分析中,为确定安全系数,运用了野外测量的孔隙压力和土层的有效强度参数。
The coastline of the Great Lakes retreated and millions of dollars were lost in the U.S. state along the tide and in parts of Canada. A number of research projects have been invested to study erosion issues. The results show that the lower part of the steep bank is the main reason for the coastline receding due to wave action. The paper studies various physical factors that cause the collapse of the steep bank. One of them is the effect of groundwater on the steep bank stability. Cliff tops of certain locations along the Lake Michigan recede 9 to 10 meters a year, and it is reported that this retreat has nothing to do with the erosion at the bottom. 25 manometers were subsequently used to measure the groundwater head and to find out the complex groundwater system in these areas. Found 5 meters above the bottom of the steep bank below the head of confined water is the glacial sediment. In the slipped moraine layer on the shore, another “stagnant water” system was discovered. Based on the record of groundwater level changes for more than a year, it was found that the water level in the underlying sand layer had fluctuated by 13 meters. The change of groundwater level has a great influence on the steep bank’s stability. In the slope analysis, in order to determine the safety factor, field pressure pore pressure and soil effective strength parameters are used.