81011362

open access

Version of Record

柵渠型排水路底面における浸透破壊 : 事例解析と防止対策工法

Seepage Failure of Bottom Soil within Double Sheet-Pile-Wall-Type Ditch : Stability Analyses and Countermeasures which are recommended

Japanese (日本語)

神戸大学都市安全研究センター研究報告

15

243-255

神戸大学都市安全研究センター

2011-03

2019-05-30

Boiling occurred in the bottom soil within a double sheet-pile-wall-type ditch (or prefabricated ditch) during puddling and the ditch border collapsed. In this case, the penetration depth was so limited that the bottom soil of the ditch became unstable when the groundwater level increased. Changes in the groundwater level were observed continuously from 2003/12/05 to 2004/04/03. The largest hydraulic head difference, H, during the continuous observation period was 0.212m on 2003/12/12. On intermittent observation, the H values ranged from 0.600m on 2004/05/16 after heavy rain to 0.456m on 2004/05/22 during puddling. The greatest H value at the time of transplanting was estimated to be 0.878m on 2004/05/24, when boiling failure occurred. FEM seepage flow and stability analyses were conducted, and the safety factor against seepage failure were calculated as Fs=1.961 (under the conditions on 2003/12/12) and 1.008 (under the conditions on 2004/05/22) when not considering backfills, Fs=1.706 (2003/12/12) and 0.864 (2004/05/22) when considering backfills. The backfills were more permeable than neighboring soils in the site. It is concluded that the bottom soil within the ditch was stable under the conditions on 2003/12/12, but was near or beyond the critical condition for seepage failure under the conditions on 2004/05/22. Three countermeasures against seepage failure were considered: (I) increase in the penetration depth of the panel; (2) decrease in the coefficient of permeability of backfills; and (3) establishing a filter (i.e., soil that is more permeable than the soil at lower depths) on the bottom ditch soil. It was found that the first method was the most effective among those methods. When the penetration depth of the panel is D=0.18m, the bottom of the ditch becomes stable against seepage failure for the maximum hydraulic head difference H=0.878m estimated at this site

浸透破壊防止対策工法

紀要論文