선행하중과 Wick Drain공법에 의한 연약해성광토의 개량

Improvement of Soft Marine Clay by Preloading and Wick Drain Method

울산만 북서측 임해지역체 발달된 연약해성점토를 개양하기 위하려 선행대중과 Wick Drain공법의 병용공법이 적용되었다. 상기 공법의 적용에 따른 연약해성점토의 거동 및 강침특성을 요명하여, 안전하고 신속하게 시공을 실시하기 위하여 현장계측에 의한 공학적인 시공관리를 실시하였다. 본 고는 연약해성점토를 개량하기 위하여 적용한 선행하중과 Wick Drain공법의 설계, 시공 및 안전관리방법을 수록하고 있다.

Preloading surcharge method along with vertical drains was adopted to improve the performance of a very soft marine clay deposit. The onshore deposit, located in the Ulsan Bay area, consists of a 2 to 10m thick, very soft, highly compressible marine clay layer developed just below. the sea water level. The initial undrained shear strength of the clay layer was about 0.6 ton/m2. But, the deposit was designed after treatment to support some auxiliary facilities for a new ilo refinery plant, requiring bearing capacities of 3.6 to 5.4 ton/m2 and maximum allowablee settlement of less than 7.5cm. A total of 35, 000 wick drains Ivas installed to expedite drainage during preloading, and surcharge loads of up to 5m above the original ground level were applied in a step-by-step loading sequence to prevent ground failure by excess surcharge loads. An extensive program of field instrumentation was implemented to monitor the behavior of the clay deposit. Measurers!ends included settlements, excess pore pressure and its dissipation, ground farmer level fluctuation, and lateral movement of the so(t clay layer under the preloads. This paper describes the design concepts, construction methods and control procedures used for improvement of the clay layer. It also presents the ground behavior measured during construction, rind comparisons with theoretical predictions.