CONTROL METHOD ANALYSIS ON FROST HEAVE WITH GEOTEXTILES AS THE EFFECT OF CAPILLARY BREAKS IN SOILS

为了开发实用的毛细断裂方法，利用几种土工布进行了室内试验，验证了其机理，并在三个冬季进行了现场调查。首先进行了毛细管上升试验，对几种土工布的性能进行了评价。然后将每条土工布放置在土柱的中高位置，保持水位不变。如果采用高截留和高霜敏感性的火山灰土，土工布对毛细断裂的影响是潜在的。在实验室冻胀试验中，试样被保持在4℃的底部，并在-6℃的温度下从顶部冻结。因此，两种厚土工布解释了水的吸收，并表明霜胀减少量低于50%。它们是具有三层结构的聚酯土工布和树脂粘合垫形织物，厚度从7.5毫米到10毫米不等。部分薄型土工布对冻胀的抑制效果不明显。野外试验采用数台溶渗仪，在离地表120 cm深的恒定水位条件下，连续3个冬季进行。土工布安装在最大霜冻穿透深度和地下水位之间。在实验室测试中使用的相同种类的厚土工布，在三个冬天里都能持久地减少霜胀。综上所述，用土工布进行毛细断裂的方法对控制冻胀具有重要的补救作用，而结构较厚的聚酯土工布对缓解土中的冻胀最为有效。

In order to develop the method of capillary breaks for the practical use, the laboratory experiments to prove the mechanism were conducted using several geotextiles, and field investigation was also carried out during three winters. The capillary rise experiment was first conduced to evaluate the potential of the several geotextiles. Then each geotextile was emplaced at mid-height in the soil column and water level was maintained at the same position. If a volcanic ash soil with high retention and high frost susceptivity was used, the potential of geotextiles was recognized for the effect of capillary breaks. In laboratory frost heave tests, the specimen was kept on the bottom at 4 C and was frozen from the too at -6 C.Consequently two kinds of thick geotextiles interpreted the uptake of water and indicated the effect of frost heave reduction by amounts below 50 percent. They were polyester geotextiles with three-layred structure and resin-bonding mat-shaped fabric, ranging from 7.5 mm to 10 mm in thickness. Some thin geotextiles did not show the effect of the reduction on frost heave. The field experiment was performed with several lysimeters under the constant water level conditions that was maintained at the 120 cm deep from the surface during three winters. The geotextiles were installed between the maximum frost penetration depth and the groundwater level. thick geotextiles, the same kinds used in the laboratory tests showed to be durable to reduce frost heave through three winters. In conclusion, it appears likely that the method of capillary breaks with geotextiles is significant for the remedies of frost heave control and the polyester geotextiles with thick structure were most effective to mitigate frost heave in soils.