Elucidation of improvement mechanism and evaluation of improvement effect on ground improved by compaction grouting

本文通过室内试验和现场试验，对压密注浆的性能进行了研究。针对实验室实验工作，研制了大型校准室。在该试验室中，制备了直径1.40m、高1.45m的砂样，并在高度模拟现场实际情况的条件下进行了固结和注浆试验，结果证实了其准确的基本性能。在现场试验方面，根据在名古屋、大阪和东京国际机场旧滑行道下进行的三次现场试验的结果进行了分析研究。本研究的主要发现如下：(1)地面隆起性能取决于注入深度。(2)表征浅层和深层注浆的临界深度取决于挤密注浆桩直径。(3)较浅的注入受锥形Shea…条件的支配更多的土体环状破坏，覆盖在被注入的土块上。在锥形剪切破坏时，所获得的注浆压力和注浆量取决于覆岩压力和抗剪强度特性。(4)在地表隆起开始前终止注浆过程，可以提高相对浅层注浆的处理效果。(5)在规划沉降构筑物和基础的提升应用的注浆工程时，只能通过低于临界深度的注浆来提供所需的提升量。(6)对于液化防治工程等应用，可在桩身较浅时注浆较小直径桩。(7)对于较深的注浆，垂直上覆压力对性能影响不大。然而，局部土体的可压缩性对其性能影响很大。如果土体相对位移变形是主要机制，则所获得的注浆压力将与局部细粒含量高度相关。如果颗粒破碎变形是主要机制，那么产生的破碎主要取决于注射压力。(8)注浆量的最大压力与静力触探试验的顶端阻力有很好的相关性。这种关联性使最大注浆压力有资格作为评价压实注浆作业性能的可靠标准。(9)在松散砂土中，加固范围仅限于注浆区周围。然而，在密实的沙子中，大面积得到了均匀的改善。较少

In this study, the performance of compaction grouting has been investigated through laboratory and field experimental works. For the laboratory experimental work, large-scale calibration chamber was developed. In this chamber, sandy samples (1.40 m in diameter and 1.45 m high) are prepared, consolidated and injected (using grout mortar) under conditions highly simulating the actual field conditions As the results, it was confirmed its accurate basic performance. As for the field tests, analytical study was involved based on the results of three field tests conducted in Nagoya, in Osaka and under the old taxiway of Tokyo International Airport.The main findings of this study are as follows : (1) The performance in terms of ground surface upheave is dependent on the injection depth. (2) The critical depth that characterizes the shallow and deep injections is dependent on the compaction grout pile diameter. (3) The relatively shallow injections are governed by the condition of conical shea … More ring failure of the soils overlying the masses being injected. At conical shearing failure, the attained injection pressure and grout volume are dependent on the overburden pressure and shear strength characteristics. (4) The treatment effectiveness of relatively shallow injections may be improved by terminating the injection process at just before the onset of ground surface upheave. (5) In planning the grouting works for the applications for lifting of settled structures and foundations, the required lifts can be provided only by the injections shallower than the critical depth. (6) For the applications such as in liquefaction prevention works, smaller-diameter piles may be injected while going shallower. (7) For relatively deep injections, the vertical overburden pressure has no appreciable effect on the performance. However, the performance is highly influenced by the local soil compressibility. If deformation by relative displacement of the soil particles is the dominant mechanism, the attained injection pressure will be highly correlated to the local fines content. If deformation by particle crushing is the dominant mechanism, the resulting crushing depends on mainly injection pressure. (8) The maximum pressure from injecting a given grout volume correlates well with the tip resistance of CPT test. This correlation qualifies the maximum injection pressure as reliable criteria for evaluating the performance of compaction grouting operations. (9) In the loose sand, the improved area is limited around the grouted area. However, the wide area is uniformly improved in the dense sand. Less