台北捷運高壓噴射灌改良土之力學性質

Abstract

本研究探討台北捷運高壓噴射灌漿改良土及其回漿的力學性質。論文第一 部分將新店線CH220 標改良土之試驗資料進行分析討論；第二部分將取自 南港線CN251 標之改良土及其回漿運回交通大學試驗室，進行超音波試驗 、單軸壓縮試驗、三軸壓縮試驗及巴西試驗，得到下述結論。由CH220 標 JSG1改良土之單軸壓縮試驗資料可知：改良土之取樣率約在53 % ∼89.5% 之間。單軸抗壓強度qu分佈範圍很廣，大約介於3.6至48.7MPa， 其中約1/3試體強度甚至大於混凝土強度3000psi(20.7MPa)。本標改良土 本標改良土qu值分佈極不均勻，可能是因為施工時灌漿壓力甚大約 (400kgf/cm^2) ，造成水泥漿在距軸心不同距離處之切割、攪拌不均勻， 因此所取得之改良土較不均質。改良土之部份單壓強度明顯高出其他已發 表資料，可能是由於硬化材流量愈大時，所得之qu隨之增加(Yahiro 1982)，本標地盤改良漿液流量240∼260 l/min，為典型灌漿流量60 l/ min之 4倍，因此強度較高。 本研究第二部分對CN251 標JSG2改良土 及其回漿進行試驗得知改良土單軸抗壓強度qu約在3.47∼6.12 MPa之間， 回漿試體之qu僅有0.44∼0.71MPa，大約是鑽孔試體單壓強度的1/5 ∼1/14 ，由於回漿是從灌漿攪拌區域上層取代出來的漿液，其中可能含 有較多之土壤顆粒，因此強度較低。由三軸試驗結果，可得改良土之凝聚 力c=0.835MPa、內摩擦角 =38.6°。本標 JSG2改良土之c 值低於JSG1改 良土者，值則與其相近，這是由於JSG2漿液是低強度之配比，因此c 值較 小。試驗結果顯示漿液內水泥量略減對改良土φ值之影響並不影響回漿試 體三軸試驗之結果，可得改良土之凝聚力c= 0.196MPa、內摩擦角16°。 回漿試體單壓強度低於鑽孔試體，因此其c、φ低於改良土者是可以預期 的。 This paper presents the properties of jet-grouted soilcrete from Taipei MRT construction. In the first part of this paper, field data from lot CH220 is analyzed and dicussed. The data from lot CH220 shows that the core recovery of JSG1 soilcrete is about 53%∼90%. The uniaxial compressive strengths of these samples vary wide from 3.6 to 48.7MPa. The variation is probably due to the high jetting pressure (400 kgf/cm^2) which made the grout cutting and mixing ununiform at different disstances from the nuzzle. The uniaxial compressive strengths of these samples are significantly higher than all published data. The high rate-of-flow of the grout (240∼260 l/min) may be the cause of the high strength as suggested by Yahiro (1982). In the second part of this paper, samples cored from lot CN251 are used to conduct the following experiments: Ultrasonic test, Uniaxial compression test,Triaxial compression test, Brazilian test. Test results from lot CN251 indicate that the uniaxial compressive strength of cored samples varies from 3.47 to 6.12 MPa.The strengths of slime samples from the same site are only 0.44~0.71MPa, which is about 1/5 to 1/14 of that for the cored samples. The slime is replaced from the upper layer of the grouted zone. Probably, it contains more soil particles, therefore result in a low stength.