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2005年日本福冈县7级地震引起大量边坡破坏。震中附近的志贺岛的环岛公路由于其上方边坡崩塌导致交通中断达1.5 a之久。其原因是崩塌边坡上方出现了较大的沉降裂缝,有可能受将来的暴雨或地震的触发再次导致边坡崩塌。根据钻孔资料及实验室实验结果,对该边坡未来可能发生的崩塌规模产生3种意见:小规模表层崩塌(A)、中规模中层崩塌(B)及大规模深层崩塌(C)。而边坡修复费用则根据所想定的可能崩塌规模从几千万日元到几十亿日元不等。为了合理决定对策规模,对3种可能的崩塌规模分别进行风险评估。结果表明,大规模深层崩塌(C)由于发生概率较小使得其风险远远小于小规模表层崩塌(A)和中规模中层崩塌(B),因而在修复中可以不予考虑。另外,虽然小规模表层崩塌(A)和中规模中层崩塌(B)的风险相当,但考虑到对策效果(加固后的风险减少与投入的加固资金费用之比),认为以小规模表层崩塌为对象制定修复计划较为合理,但在部分区域可考虑有关针对中规模中层崩塌的对策。本提案被相关部门所采用。
2005 Japan Fukuoka Prefecture magnitude 7 earthquake caused a large number of slope damage. Shiga Island near the epicenter island road due to the collapse of the slope above the traffic led to traffic interruption for 1.5 a long time. The reason is that there is a large settlement crack above the collapsed slope, which may be triggered by future heavy rain or earthquakes to cause the slope to collapse again. According to the borehole data and experimental results, there are three opinions on the possible collapse scale of the slope: small-scale surface collapse (A), medium-scale collapse (B) and large-scale deep collapse (C). The slope repair costs according to the size of the collapse may be from tens of millions of yen to billions of yen range. In order to rationally determine the scale of the countermeasure, risk assessment is conducted on each of the three possible collapse scales. The results show that the large-scale deep collapse (C) can not be considered in the repair due to its smaller probability of occurrence than small-scale surface collapse (A) and middle-scale collapse (B). In addition, although the risk of small-scale surface collapse (A) and middle-scale collapse (B) is comparable, considering the countermeasure effect (the ratio of the reduced risk reduction to the capital cost of investment), it is considered that small- It is more reasonable for the target to formulate a restoration plan, but some areas may be considered for countermeasures against the middle-level collapse. This proposal is adopted by the relevant departments.