지반앵커 시험의 성능평가 기준에 대한 고찰

Abstract

In this study, the performance evaluation tests that are to be conducted for tension ground anchor and compression ground anchor were summarized, analyzed and evlauated. The performance evaluation criteria for tension ground anchor are divided into temporary and permanent anchors. In the case of the temporay anchor, 10% of the elastic displacement of anchor tendon is set as the upper limit larger than that of the permanent anchor. This is because the temporary anchor is mainly settled in the soil and is presented in consideration of the short period of use. Therefore, the performance evaluation criteria of tension ground anchor may apply the currently presented upper and lower limits as they are. The performance evaluation criteria of compression ground anchors do not distinguish between temporary and permanent anchors, and 10% of the elastic displacement of anchor tendon is presented as the shear friction displacement limit at the anchor bond length. Conventionally, the compression ground anchor has been mainly used as a permanent anchor, but when the compression ground anchor is used as a temporary anchor, it is necessary to prepare a separate performance evaluation criteria for the temporary anchor. When a compression ground anchor is used as a temporary anchor which is mainly settled on the soil, and the conventional upper limit is too strict for a temporary anchor. Thus, it is necessary to prepare an upper limit more suitable for the conditions of use. In the case of using a compression ground anchor as a temporary, it is appropriate to apply the upper limit, which increases the elastic displacement by 10% more than the current upper limit, considering that there is a 10% difference from the tension ground anchor. However, since it must be confirmed that no pull-out displacement is occurring at the ground anchor, it must be premised that the anchor tendon, whose load-displacement curve shows that only the shear friction displacement of the anchor bond length maintains an elastic state. In addition, the load distribution of compression ground anchor is widely used in Korea. There is an error in the application of the length of the anchor tendon applied to the performance evaluation, which leads to incorrect performance evaluation. As a result of investigating the upper and lower limits for performance evaluation of the load distribution of compression ground anchor, it was found that the upper and lower limits are significantly different for each anchor with different lengths of anchor tendon. Therefore, when performing the performance evaluation of the load distribution of compression ground anchor, the evaluation should be made for each upper and lower limit in consideration of the length of the anchor tendon actually used for each anchor.