逆打工法における注入法打継ぎ処理に関する研究

抄録

The top down construction method involves several particular technical problems, such as (1) the joint treatment of top down concreting, (2) the influence of heaving, due to excavation, on the concrete structutre, (3) the temporary supporting mehtod of the weight of upper floors during underground work;the weight must be supported by steel column in cast-in-place concrete pile. In particular, the construction joint of concrete have been a matter of concern since the introduction of the method. Joints created by the top down concreting produce a layer of laitance and setting of lower part of concrete causes detachment of the joints, which weekens the structure and reduces watertightness. In Japan three types of joint treatment method have been adopted, which are (1) Direct mehtod ; A concrete of normal mixture or that containing non-bleeding or expansive additive is used for the lower part. (2) Injection method ; Cement paste or epoxy resin is injected into the clearance which is produced by setting of concrete. (3) Filling method ; Non-shrinking mortar is filled in the clearance (about 300mm) between the upper and lower concrete. In this report a new type of the injection method, which was developed by the authors based on the conventional injection method, is proposed, and it's efficiency is descrived. The reasults obtained in this study are summarized as follows. 1) The most suitable clearance to inject cement paste is 3mm 2) The suitable interval of injection holes is about 600mm 3) The pressure of injection should be taken 4〜8kgf/cm^2