Geotextiles with natural fibers like coir, jute, sisal, hemp, etc. are used in many non-critical civil engineering applications like erosion control. The main advantage of geotextiles with natural fibers is that they are ecofriendly and biodegradable. They can be successfully used in limited life applications of geotechnical engineering. This paper deals with some case histories on the use of woven and stitched non-woven coir blankets for erosion control and slope stabilization, executed by the authors.
The ground freezing method is a ground improvement technique used as temporary work such as in shield tunnel construction. This chapter introduces two projects using the ground freezing method in Japan. One is a case adopted to remove the existing steel sheet piles under the subway tunnel structure; the other is a case adopted as shield arrival protection work of a discharge tunnel in the thermal power plant station. In the former case, it was necessary to excavate an adit under the existing subway tunnel structure in order to remove the existing steel sheet pile. The ground freezing method was adopted as a protection work for excavation of the adit. In the latter case, a newly developed CO2 ground freezing method was adopted for the first time in the world, in order to cut off water at arrival point of the shield to build discharge tunnels. The ground freezing method of the CO2 has advantages such as lower temperatures and smaller freezing facilities as compared with the conventional method, in addition to reducing environmental loads. In this case, the construction period was shortened utilizing the advantage of CO2 system.
The historical ruins, which consisted of rocks or soils, are treated for their preservation. In many cases, the ground improvement techniques are being used for the preservation of them. One tower of Angkor ruins was deemed as the most dangerous tower among them for restoration work. The compacted sandy formation was found from −1.5 m from the original ground surface and to +3.5 m above the ground. The safety factor for the ground bearing capacity in rainy season was calculated with S.F = 1.1. When its bearing strata were reconstituted, it was designed to have a sufficient safety factor value of S.F > 1.5. To achieve this purpose, the original sandy soils were mixed with slaked lime and compacted by tamping with geotextile. The material soil used for the platform was a mixture of different soils of original sandy soil, clayey soil, and lateritic soil at weight ratios of 70, 15, and 15%. Slaked lime was added to the mixed soil 1 at a rate of 0.1.
