以高壓噴射灌漿工法改良土壤之工程性質

Abstract

本論文探討高壓噴射灌漿改良土的各項工程性質。本研究第一部份自台北市杭州南路衛生下水道次幹管工程之JSG地盤改良施工現場，取得改良土之鑽心試體，於交通大學岩石力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，獲得以下各項結論： 1、 改良土之乾密度對其力學性質之影響甚為明顯。若其乾密度增加，其單壓強度、彈性模數、破壞應變、張力強度、壓力波速及剪力波速均隨之增大。 2、 改良土的單軸壓縮強度qu 在 3.02至 8.72 MPa 之間；彈性模數( Et,50 )介於1.11 ~ 4.77 GPa之間；改良土柏松比□50介於 0.05 至 0.29 之間，與混凝土之柏松比 (0.1~0.2) 相接近。 3、 以巴西試驗所得之改良土張力強度值為0.21~0.87 MPa，統計國內外噴射灌漿形成改良土張力強度介於0.20~0.95 MPa之間，本試驗結果，大致與上述張力強度範圍相符合。 4、 依據本研究之三軸壓縮試驗結果，可獲得改良土之之凝聚力c = 0.73 MPa，內摩擦角 □□□□□□□。。 本研究第二部分自國內外已發表之期刊及研討會論文集中，廣泛的收集有關噴射灌漿改良土工程性質之案例資料共計63組，進行分析研究，並獲得以下各項結論： 1、 在不同土層中進行土壤改良，得到改良土單軸壓縮強度之範圍不同，在泥炭土中形成改良土之單軸壓縮強度上限值僅在3.0 MPa以內。粘土質改良土，其單軸壓縮強度範圍介於0.4~12.0 MPa之間。砂土質改良土qu值在0.4~26.0 MPa之間。 2、 改良土單軸壓縮強度顯然不僅受到漿液灰水比的影響，因此不宜以過份簡化的公式預估改良土之qu值，而必須通盤考量土壤種類、灌漿方式、漿液配比、施工機具等多項因素之影響。 3、 日本JSG協會( 1986 ) 建議，於砂質土壤採用雙重管JSG-1( C/W = 1.0 )之要求最低單壓強度為3 MPa，於凝聚性土壤內形成之改良土最低要求強度為1 MPa。於砂質土壤採用JSG-2( C/W = 0.4 )工法形成改良強度為1 MPa，於凝聚性土壤內形成之改良土強度建議為0.5 MPa。依本研究統計結果可知，JSG協會的建議值顯然是作為施工檢驗時，要求之下限值。 4、 改良土之強度愈大，其勁度亦愈大。礫石改良土之單壓強度明顯大於黏土質改良土之qu值。

In this thesis, the mechanical properties of jet-grouted soilcrete are investigated. In the first part of this paper, samples cored from Taipei sewerage construction were used to conduct the following experiments : ultrasonic test, uniaxial compression test, triaxial compression test, and Brazilian test. Base on the experimental results, the following conclusions are made : 1. The mechanical behavior of soilcrete is significantly affected by its dry density. The uniaxial compressive strength, modulus of elasticity, failure strain, tensile strength, compressive wave velocity, and shear wave velocity of soilcrete increased with increasing dry density. 2. The uniaxial compressive strength of soilcrete varied from 3.02 to 8.72 MPa. The modulus of elasticity of soilcrete varied from 1.11 to 4.77 GPa. The Poisson’s ratio of soilcrete varied from 0.05 to 0.29, which were close to the values for concrete ( 0.1 to 0.2 ). 3. Based on Brazilian tests, the tensile strength of soilcrete varied from 0.21 to 0.87 MPa, which were close to the values reported in many different articles published data ( σt,B = 0.20 ~ 0.95 MPa ). 4. Test data from triaxial compression tests indicated that the cohesion of the soilcrete is 0.73 MPa, and the internal friction angle is 38.70. In the second part of this paper, cases reporting of the mechanical properties of jet -grouted soilcrete were been collected. Base on the field data, the following conclusions are made: 1. The uniaxial compressive strength of soilcrete was significantly affected by the type of native soil. For soilcreted formed peat, the upper limit of qu was only 3 MPa. For soilcrete formed in clay, the range of qu varied from 0.4 to 12.0 MPa. For soilcrete formed in sand, qu = 0.4 ~ 26.0 MPa. 2. The uniaxial compressive strength of soilcrete can not be properly estimated only with the c/w ratio of the grout. 3. Most of the uniaxial compressive strengths of soilcrete reported in the literature were higher than that suggested by the JSG Association. It is clear that the qu values suggested by JSG Association are the minimum strengths required for quality control of construction. 4. The modulus of elasticity of soilcrete increases with increasing uniaxial compressive strength. The qu of soilcrete formed in gravel is higher than that formed in clay.