Experimental study of groutability of Super-Micro cement
Based on the similarity theory and the theory of model test, we simulate different opening rock fractures indoors. On account of Super-Micro cement with four different water cement ratios of 0.8, 1.0, 1.5, 2.0 under different water reducer and additive, the experiment is testing the passing rate of Super-Micro cement through the filter with diameters of 0.02mm, 0.05mm, 0.07mm. The test results indicate that the ultimate limit viscosities are 17.1mPa.s, 33.6mPa.s and 624.7mPa.s respectively when the superfine cement passes these three filtrations. After analyzing the influence of grout viscosity on passing rate, that is to say, the bigger the viscosity, the smaller the crack width.
In-Place Treatment of Foundation Soils
The state-of-the-art of seven special methods for the treatment of soils for the support of structures is reviewed. Whereas vibroflotation, compaction piles, blasting and grouting are limited mainly to the treatment of cohesionless soils, electro-osmosis, thermal treatment, and treatment with additives find primary application in the treatment of cohesive soils. Although blasting is usually the fastest and least expensive, compared with vibroflotation and compaction piles, the results are the least certain. Installation of stone column piles by vibroflotation has extended the range of application of this method into cohesive soils. Recently developed chemical grouts are now approaching the ideal in terms of viscosity and control of setting time. Mixed-in-place intrusion grouting appears to be a promising technique for construction of soil-cement piles in place. Additive stabilization of foundation soils for structures is used mainly in connection with grouting and electro-osmosis, with additional application to the treatment of expansive soils to shallow depths.
GROUTED CUTOFF CURTAINS IN FISSURED ROCK
THE EFFECT OF GROUT CURTAINS ON SEEPAGE IS VERY OFTEN OVERESTIMATED AND IN MOST CASES LITTLE IS KNOWN ABOUT THE FLOW NETS BELOW DAMS. THE AUTHOR STATES THAT THE STATISTICAL DISTRIBUTION OF JOINTS AND FISSURES PERMITS THE SEEPAGE PROBLEM TO BE CONSIDERED AS A GRAVITATIONAL POTENTIAL FLOW THROUGH A HOMOGENEOUS POROUS MEDIUM (DARCY'S LAW). NEVERTHELESS THE DETERMINATION OF K (FOR INSTANCE BY MEANS OF THE LUGEON TEST) IS QUITE DIFFICULT, MAINLY DUE TO THE OPENING OF THE FISSURES WITH THE IMPOSED PRESSURES AND BECAUSE THE WEIGHT OF THE DAM TENDING TO CLOSE THE JOINTS IS ABSENT IN THE TEST. GROUTING TESTS AND THE METHOD KNOWN AS "SPLIT SPACING" ARE ALSO RECOMMENDED. WITH REFERENCE TO GROUTING PRESSURES, THE DATA GATHERED FROM SOME PROJECTS SHOW THAT THE SAFE PRESSURE RANGES FROM 2 TO 4 TIMES THAT OF THE OVERLOAD, DOWN TO 50 M DEPTH - WITHOUT EXCEEDING 60 TO 70 ATM FOR DEPTHS BETWEEN 100 AND 200 M. THE AUTHOR CONCLUDES THAT AN AVERAGE PERMEABILITY OF K X 10 TO THE 6TH CM/S IS SELDOM ATTAINED WITH GROUT CURTAINS. THE USE OF MODELS OR COMPUTERS PERMITS THE STUDY OF THE EFFECT OF DEPTH AND THICKNESS OF THE GROUTED ZONE ON THE SEEPAGE PATTERN. /RRL/