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DEEP COMPACTION

DEEP COMPACTION.

randall-hopkins
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DEEP COMPACTION

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  1. DEEP COMPACTION CE-464 Ground Improvement THE MAIN PURPOSE OF TREATING OR IMPROVING THE SOILS IS TO ELIMINATE THE DANGER OF EXCESSIVE SETTLEMENTS. LOOSE COHESIONLESS SOILS GENERALLY DO NOT POSE SERIOUS PROBLEMS IN TERMS OF STABILITY AND SETTLEMENT. LIQUEFACTION IS THE MAIN CONCERN FOR LOOSE COHESIONLESS SOILS UNDER WATER TABLE. OTHER DYNAMIC LOADS ALSO AFFECT THESE SOILS. METHODS FOR COHESIONLESS SOILS : - VIBROCOMPACTION TECHNIQUES - COMPACTION PILES - BLASTING

  2. 1. VIBROFLOATATION CE-464 Ground Improvement THIS IS NOT A NEW METHOD. (50 YEARS OLD). THE EQUIPMENT HAS THREE ELEMENTS. A) THE VIBRATOR OR VIBROFLOT B) EXTENSION TUBES C) CRANE (-T-WATER JET SUPPLY WATER, PUMP+GENERATOR, CABLES). VIBROFLOT IS A CYLINDRICAL PROBE WHICH PENETRATES INTO THE GROUND WITH THE AID OF VIBRATION (VERTICAL AND/OR HORIZONTAL) AND ITS OWN WEIGHT AND JETTING (WATER MOSTLY, FOR DEEP PENETRATIONS AIR OR AIR AND WATER).

  3. CE-464 Ground Improvement VIBROFLOT DIAMETERS ARE IN THE RANGE OF 0.35 - 0.50 m, LENGTHS 2-6 m. AN ECCENTRIC MASS IS AT THE LOWER PART OF THE VIBRO PROBE WHICH IS A HOLLOW STEEL TUBE WEIGHTS OF VIBROFLOTS ARE USUALLY IN THE RANGE OF 20 - 40 kN (2-4 ton) AND THEY DEVELOP HORIZONTAL CENTRIFUGAL FORCES OF 80-160 kN. VIBRATION AMPLITUDES ARE UP TO 20-25 mm AND USUAL OPERATING FREQUENCIES ARE 30-50 Hz (1800 - 3000 rpm) (35-100 kW POWER) WATER JETS MAY BE APPLIED AT TOP AND/OR BOTTOM.

  4. CE-464 Ground Improvement

  5. CE-464 Ground Improvement TYPICAL VIBROFLOT PENETRATION RATES: 1-2 m/mIn, VIBROFLOT WITHDRAWAL / COMPACTION RATES : 0.3 m/mIn. WATER JETTING PRESSURES UP TO 800 kN/m2, FLOW RATES UP TO 3000 lt/mIn (50 lt/sec). SAND BACKFILL IS SUPPLIED AT A RATE UP TO 1.5 m3/m RADIUS OF INFLUENCE, R FROM THE VIBRATOR DEPENDS ON THE TYPE OF VIBRATOR AND SOIL TYPE 0.6–0.9 m FOR 20 % OR MORE SMALLER THAN NO. 200 SIEVE AND 2 m FOR CLEAN SANDS.

  6. CE-464 Ground Improvement MOST EFFECTIVE IN CLEAN SANDS, HOWEVER WEBB & HALL (1968) REPORT GOOD SUCCESS IN SOILS CONTAINING APPRECIABLE PORTIONS OF SILT AND CLAY AS MUCH AS 30%. CAQUAT - KERISEL (1966) RECOMMEND COARSE SAND, GRAVEL OR COBBLES AS FILLING MATERIAL. WHEN DENSIFYING FINE SANDS AND SILTY SAND COARSE PARTICLES ARE MORE EFFECTIVE TO IMPROVE TRANSMISSION OF VIBRATION TO SURROUNDING SOIL BETTER. THERE ARE ALSO CASES ON RECORD WITH VERY FINE SAND, FINE SAND WITH LENSES OF MUD, FINE SAND WITH BALLS OF CLAY AND SILTS AND SANDS WITH CLAY LAYERS UP TO A METER.

  7. CE-464 Ground Improvement

  8. CE-464 Ground Improvement RELATIVE DENSITY, Dr,OF AT LEAST 70 % CAN BE OBTAINED BETWEEN CENTERS. INCREASE IN RELATIVE DENSITY IS BETWEEN 20% - 40%. qall AFTER TREATMENT IS USUALLY AROUND 2 - 3 kg/cm2 (COST ROUGHLY 2- 4 $/m3 USA RATE). THE DESIGN OF A VIBROFLOATATION TREATMENT REQUIRES SPECIFICATION OF THE DESIRED RELATIVE DENSITY AND THE PATTERN AND SPACING OF VIBROFLOT HOLES. A RELATIVE DENSITY OF AT LEAST 75 % HAS BEEN A FREQUENTLY USED REQUIREMENT TO INSURE AGAINST EXCESSIVE SETTLEMENT OR LIQUEFACTION, HOWEVER THE VALUE SPECIFIED IS A FUNCTION OF THE TYPE OF PROJECT AND THE LOCAL CONDITIONS.

  9. CE-464 Ground Improvement D'APPOLONIA, MILLER AND WARE (1955) SUMMARIZE SOME OF THEIR FINDINGS; TRIANGULAR PATTERN PREFERRED DUE TO GREATEST COMPACTION EFFORT OVERLAP. D, IS NOT INCREASED ABOVE 70% AT POINTS MORE THAN 1 m FROM A SINGLE VIBROFLOT COMPACTION. THE OVERLAPPING EFFECT FOR SPACINGS GREATER THAN 2.4 m IS SMALL. SPACINGS LESS THAN 1.8 m SHOULD GIVE Dr HIGHER THAN 70 % WITHIN THE COMPACTED AREA. THE EFFECT OF ADJACENT COMPACTIONS CAN BE SUPERIMPOSED. THERE ARE PROCEDURES FOR DETERMINING VIBROFLOT SPACING REQUIRED TO OBTAIN A SPECIFIED Dr (mIn.) .

  10. CE-464 Ground Improvement WEBB & HALL (1968) ALSO DESCRIBE A METHOD FOR SILTY AND CLAYEY SAND. A SPACING OF 2.1 – 2.4 m IS OFTEN CHOSEN. CLEAN COARSE SANDS AND COARSER SOILS MAY REQUIRE 2.4 m OR MORE. FINER MATERIAL AND MATERIAL CONTAINING CLAY INCLUSIONS MAY REQUIRE MUCH CLOSER SPACINGS. RANGE (1.5 -3M) DEPENDS ON; - TYPE OF SOIL AND BACKFILL - PROBE TYPE AND ENERGY - LEVEL OF IMPROVEMENT REQUIRED

  11. 2. VIBRATING PROBES CE-464 Ground Improvement VIBRATORY PIPES OR PROBES MAY BE PUSHED INTO THE SOIL TO DENSIFY THE SOIL LAYERS WITHOUT ADDING MATERIAL AT DEPTH, ONLY SURFACE ADDITION IS DONE. ANDERSON(1974) USES PILE VIBRO-DRIVER HAMMER ON TOP OF A 0.76 m DIAMETER PIPE PILE (3-5 m LONGER THAN THE DEPTH OF TREATMENT). TYPICAL APPLICATION CHARACTERISTICS ARE; FREQUENCY 15 Hz, VERTICAL AMPLITUDE 10-25 mm, APPROXIMATELY 15 Probes /hr, 1-3 m SPACING, UPPER FEW METERS ARE NOT EFFECTIVELY DENSIFIED. SAITO (1977) USES AGAIN VIBRATORY PILE DRIVING HAMMER AND VIBRO-RODS

  12. CE-464 Ground Improvement

  13. 3. VIBRO - COMPOZER METHOD COMPRESSED AIR IS USED INSIDE THE CASING TO HOLD SANDIN PLACE WHILE WITHDRAWINGTHE CASING MURAYAMA(1958) CE-464 Ground Improvement

  14. 4.SOIL VIBRATORY STABILIZING METHOD (SVS) CE-464 Ground Improvement IN SVS VERTICAL VIBRATION AND HORIZONTAL VIBRATION ARE APPLIED. SIMILAR TO VIBROFLOT SAND BACKFILL USED, WATER IS NOT USED.

  15. 5.COMPACTION PILES CE-464 Ground Improvement DENSIFICATION FROM TWO EFFECTS DISPLACEMENT OF SOIL VIBRATION DURING DRIVING A CASING WITH DETACHABLE (LOST POINT) END PLATE OR WITH A SPECIAL OPENING MECHANISM AT THE TIP IS DRIVEN BACKFILL IS FILLED AS THE CASING IS WITHDRAWN. USUALLY 0.9 - 1.5M SPACING IS USED. BETTER IN FULLY SATURATED OR DRY SANDS.

  16. CE-464 Ground Improvement FRANKI MACHINES AND TECHNIQUE ARE ALSO VERY SUITABLE TO FORM SAND OR GRAVEL PILES. IF THE PERMEABILITY OF THE SOIL IS NOT HIGH, SAND OR GRAVEL PILES ALSO ACT AS DRAINAGE COLUMNS SAND DRAINS TO ACCELERATE SETTLEMENTS ARE DIFFERENT CONCEPT AS WE HAVE DISCUSSED PREVIOUSLY HORIZONTAL EXTENT OF THE COMPACTED ZONE ALONG THE SHAFT IS ABOUT 5 RADII. FRANKI TECHNIQUE IS MORE EFFECTIVE THAN A DRIVEN PIPE, MEYERHOF (1959).

  17. SUITABILITY OF SOILS AND METHODS CE-464 Ground Improvement SOIL TYPE, GRADATION, FINES CONTENT ETC. DEGREE OF SATURATION, LEVEL OF G.W.T INITIAL DR s’V0 , s’H0 (OCR, sVMAX) INITIAL SOIL STRUCTURE, CEMENTATION, AGE ETC. SPECIAL CHARACTERISTICS OF THE METHOD USED VIBROCOMPACTION METHODS ARE BEST SUITED TO CLEAN COHESIONLESS SOILS WITH 20-25% MAXIMUM FINE CONTENT DUE TO LOW PERMEABILITY AND COHESION IN LOESS, SILTY SANDS WHERE FINES ARE HIGH IN %, TRY OTHER TECHNIQUES LIKE HEAVY TAMPING (DYNAMIC CONSOLIDATION)

  18. CE-464 Ground Improvement EVALUATION OF THE TREATED GROUND MAY BE DONE BY ONE OR TWO OF THE FOLLOWING METHODS; SURFACE SETTLEMENT MARKERS VOLUME OF ADDED SOIL (CRATERS OR VIBROCOMPACTION DISP.) STANDARD PENERATION TEST, SPT. CONE PENETRATION TEST, DUTCH CONE, CPT PRESSUREMETER TEST, PMT SEISMIC SHEAR WAVE VELOCITY DETERMINATIONS, VS PILE DRIVING RESISTANCES PLATE LOADING TESTS DOWN - HOLE DENSITY METERS.

  19. CE-464 Ground Improvement

  20. VIBROCOMPACTION GRIDS ARE SQUARE OR TRIANGULAR ASSUMING DENSIFICATION ONLY IN LATERAL DIRECTION (D<80CM)SQUARE TRIANGULAR (CONSIDER AVERAGE De) CE-464 Ground Improvement

  21. CE-464 Ground Improvement

  22. BROWN (1977) HAS DEFINED A SUITABILITY NUMBER FOR VIBROFLOATATION BACKFILLS. D10, D20 and D50 ARE MM PARTICLE SIZES CORRESPONDING % PASSING. SUITABILITY NUMBERS AND BACKFILL CLASSES CE-464 Ground Improvement

  23. DYNAMIC CONSOLIDATION OR HEAVY TAMPING (POUNDING) CE-464 Ground Improvement FIRST APPLICATIONS 1970 - 1973 BY MENARD. IT IS REPEATED DROPPING OF A HEAVY WEIGHT ON TO THE SURFACE OF THE SOIL TO COMPACT IT. WEIGHTS (OR POUNDERS) USED MAY BE CONCRETE BLOCKS, TOUGHENED STEEL PLATES BOLTED TOGETHER OR THICK STEEL SHELLSFILLED WITH CONCRETE OR SAND AND MAY RANGE BETWEEN 1/2 - 200 TONS. DURABILITY OF THE WEIGHT ISIMPORANT BECAUSE OF LARGE NUMBER OFDROPS. DROP HEIGHTS (H) ARE UP TO 40 M AND SQUARE OR CIRCULAR SHAPES IN PLAN ARE USED.

  24. CE-464 Ground Improvement B(WIDTH) OR D (DIAMETER) IS FEW METERS AND DEPENDS ON • WEIGHT REQUIRED • MATERIAL • BEARING CAPACITY OF THE SOIL A TYPICAL APPLICATION H = 20 M AND W = 15 - 20 TON DEPTH OF COMPACTION = 10 M. USUALLY LARGE AREAS (NOT VERY CLOSE TO POPULATED AREAS) ARE SELECTED TO APPLY HIS METHOD. USUALLY RECTANGULAR GRID POINTS 5-10 M APART ARE USED, 5-10 BLOWS OF THE TAMPER ARE APPLIED AT EACH POINT. THE NUMBER OF BLOWS AT A POINT IS CONTROLLED PRIMARILY BY THE OBSERVATION OF THE DEPTH OF DEPRESSION CREATED.

  25. CE-464 Ground Improvement A TYPICAL TREATMENT : AVERAGE 2-3 BLOWS /m2 2 OR 3 COVERAGES OF AN AREA MAY BE REQUIRED. THE TIME INTERVAL BETWEEN COVERAGES DEPENDS ON THE RATE OF DISSIPATION OF EXCESS POREWATER PRESSURES AND STRENGTH REGAIN. EXAMPLE FOR COARSE SAND DAYS AND FOR FINE GRAINED SOIL WEEKS MAY BE NECESSARY. GROUND SURFACE IS USUALLY LEVELLED BETWEEN COVERAGES BY IMPORTED GRANULAR MATERIAL. BEFORE FURTHER PASSES OF TAMPING, MEASUREMENTS ARE DONE AFTER LEVELLING TO ASSESS AVERAGE FORCED SETTLEMENT ( DS : 2 - 5 % PER COVERAGE). TO ASSESS THE TRUE VOLUME COMPRESSION MEASUREMENTS AND CALCULATIONS ARE DONE AT SELECTED POINTS.

  26. CE-464 Ground Improvement

  27. CE-464 Ground Improvement BEFORE STARTING TAMPING A SURFACE BLANKET OF UNSATURATED GRANULAR MATERIAL I M THICK OR MORE IS SPREAD OVER THE AREA TO BE TAMPED IF THIS DOES NOT OCCUR NATURALLY TO LESSEN LOCAL SHEAR & TO ALLOW EFFECTIVE COMPACTION. "IRONING" IS FULL COVERAGE OF THE AREA BY SMALL IMPACTS. IT COMPACTS THESURFACE LAYERS (H = 2-3 M). IT CAN BE DONE BY SURFACE ROLLING.

  28. CE-464 Ground Improvement

  29. CE-464 Ground Improvement

  30. ECONOMIC DEPTH BELOW BLANKET: 3-10 M. • S(NO IMPROVEMENT) / S(AFTER TAMPING) = 4-5 • NOTE THAT IMPROVEMENT IS NOT UNIFORM WITH DEPTH. • PRELIMINARY TESTS (TRIAL) ARE NECESSARY. • A SUITABLE METHOD OF CONTROLLING THE COMPACTION IS ESSENTIAL (PRE&POST TESTS) • GENERALLY IT IS BELIEVED THAT PLASTIC SATURATED CLAYS ARE NOT SUITABLE FOR TAMPING. LOW PLASTICITY COHESIVE SOILS MAY BE SUITABLE. CE-464 Ground Improvement

  31. wave propagation under impact (after R.D.WOODS) CE-464 Ground Improvement

  32. BLASTING CE-464 Ground Improvement PRINCIPLE OF THE METHOD: BY BLASTING BURIED EXPLOSIVES (DYNAMITE, TNT, AMMONITE ETC.) LONGITUDINAL AND SHEAR DETONATION WAVES ARE PRODUCED. APPLIED TO MAINLY LOOSE, COHESIONLESS, SATURATED SOILS (MOST SUITABLE) BLASTING CAUSES LIQUEFACTION, AND THEREFORE SOIL STRUCTURE IS BROKEN AFTER BLASTING, WATER AND GAS IS EXPELLED. DENSIFICATION OCCURS SAND BOILS AT THE SURFACE (CRATERING IS AVOIDED)

  33. PROCEDURE : • PIPE IS INSTALLED TO THE DESIRED DEPTH (BY JETTING, VIBRATING ETC.). • CHARGE IS PLACED IN THE PIPE. • PIPE IS WITHDRAWN AND THE HOLE IS BACKFILLED (SOMETIMES PIPES ARE LEFT IN PLACEAND FIXED LATER ON). • THE CHARGES ARE DETONATED ACCORDING TO THE PRE-ESTABLISHED PATTERN. CE-464 Ground Improvement

  34. CE-464 Ground Improvement MAJOR SETTLEMENT FOLLOWS THE BLAST, SMALLER SETLEMENTS LAST FOR THE NEXT FEW MINUTES. PIEZOMETERS ARE USUALLY INSTALLED. DENSER (STRONGER) THE SAND AND HIGHER DR AND GREATER THE REQUIRED DEPTH FOR DENSIFICATION NEEDS GREATER AMOUNTS OF EXPLOSIVES (BLAST) TO BE USED (I.E. HIGHER ENERGY REQUIRED). SUITABILITY AS FAR AS GRAIN SIZE DISTRIBUTION IS CONCERNED IS SAME AS VIBROFLOATATION. LYMAN REPORTS EFFECTIVENESS IN SILTY SOILS. WILD & HASLAM FOUND THE METHOD EFFECTIVE IN A MICACEOUS SAND (75 % OF THE PARTICLES SMALLER THAN NO: 200 SIEVE). PRUGH FOUND THAT CLAY POCKETS REDUCE THE EFFICIENCY DRASTICALLY.

  35. PARTLY SATURATED SOILS MAY BE SATURATED ARTIFICIALLY. NO GENERALLY ACCEPTED DESIGN PROCEDURES ARE AVAILABLE. CONDUCT FIELD TRIALS AND/OR FOLLOW GENERAL GUIDELINES FROM PREVIOUS EXPERIENCES AND STUDIES FOR A GOOD APPLICATION. IVANOV (1967) EXPERIENCES UP TO 20 M DEPTH. • CHARGE SIZE : < 1 - 12 kg • DEPTH OF BURIAL ‘D’ (CENTER OF CHARGE) D> H/4 - D=H ANOTHER RECOMMENDATIOND = 0.67 H CE-464 Ground Improvement

  36. CE-464 Ground Improvement CHARGE SPACING IN PLAN : 3-15 m NUMBER OF COVERAGES : 1-5 (2-3 usual) EACH COVERAGE CONSISTSOR A NUMBER INDIVIDUAL CHARGES. TOTAL EXPLOSIVE USE : 8-150g/m3 (10-30 g/m3 typical) SURFACE SETTLEMENT : 2-10 % of layer thickness DEPTH OF TREATMENT : VARIABLE, APPLICATIONS UP TO 30-40 m ARE QUOTED;PRACTICAL LIMIT: TO PLACE THE REQUIRED CONCENTRATED CHARGES TO THE REQUIRED DEPTH.

  37. CE-464 Ground Improvement AS 'H' INCREASES s0 AND Dr ALSO INCREASE WITH INCREASING ENERGY REQUIRED, DECREASING RADIUS OF INFLUENCE. IVANOV 1987 where ; Pmax IS THE MAGNITUDE OF SHOCK WAVEPRESSURE(kg/cm2) C IS THE SIZE OF CHARGE, (kg of TNT) R IS THE DISTANCE FROM CENTRE OF CHARGE (m) m1, m2, k1, k2ARE EMPIRICAL COEFFICIENTS. ‘I’ IS THE IMPULSE PER UNIT AREA (kg.sec/cm2). SOMETIMES THE RATIOIS CALLED HOPKINSON'S NUMBER.

  38. EVEN SMALL % GAS CAUSES DAMPING OF P - WAVE PRESSURES. • DENSIFICATION UP TO 75-80 % DR HAS BEEN POSSIBLE, SOMETIMES ERRATIC RESULTS OCCUR, INITIALLY DENSE LAYERS MAY BE LOOSENED. • UPPER 1 - 2 m NOT EFFECTIVE AND COMPACTED BY SURFACE ROLLERS. CE-464 Ground Improvement

  39. CE-464 Ground Improvement LYMAN, 1942 GIVES THE FOLLOWING RELATIONSHIP BETWEEN WEIGHT OF CHARGE, C, IN LBS AND RADIUS OF SPHERE OF INFLUENCE, R(ft), C = a* R3 a = 0.0025 (0.062 m/ kg) for 60% Dynamite THE SIZE OF THE CHARGE ‘C’ (IN KG TNT) CAN BE TAKEN AS, ACCORDING TO IVANOV, 1978; C = 0.055 * d3chwhere d3chIS THE DEPTH OF CHARGE PLACED. KOK & TRENSE, 1979 BASED ON PRACTICAL EXPERIENCE THE EFFECTIVE RADIUS, Reff (IN m) OF THE INFLUENCE OF BLASTING (DEFINED AS THE RADIUS WITHIN WHICH FAIRLY UNIFORM COMPACTION OCCURS AND APPROXIMATES THE BASE OF THE SETTLEMENT SAUCER) CAN BE EXPRESSED AS; where K=2-5

  40. CE-464 Ground Improvement AS A RESULT OF BLASTING, LIQUEFACTION OCCURS WHICH IS THE POTENTIAL FOR DENSIFICATION. LIQUEFACTION COEFFICIENTDu/s’0 Du : EXCESS POREWATER PRESSURE s’0 : EFFECTIVE OVERBURDEN PRESSURE PRIOR TO BLASTING IF DEPTH EFFECT IS DISREGARDED : KOK & TRENSE, 1979 LIQUEFACTION OCCURS WHEN Du/s’0 APPROACHES TO UNITY.

  41. This gives a mean value for the radius of liquefaction CE-464 Ground Improvement

  42. BARENDSEN & KOK (1983): IF THEN NO BOILING. CE-464 Ground Improvement

  43. THE MINIMUM DISTANCE R OF THE CHARGE CAN BE DEDUCED CE-464 Ground Improvement

  44. EXPERIMENTALLY FOR AMSTERDAM HARBOUR: CE-464 Ground Improvement ACCORDING TO IVANOV (I983) OPTIMUM VALUE OF SUCH CHARGES WOULD BE AT THE ORDER OF ABOUT 10 KG TNT. HOPKINSON NUMBER IS ALSO A MEASURE OF SETTLEMENT OF THE SOIL LAYER, WITH INITIAL THICKNESS H, WHEN TREATED WITH EXPLOSIVES;

  45. CE-464 Ground Improvement AFTER BLASTING PENETRATION RESISTANCES IN LOOSE SOILS DO NOT INCREASE IMMEDIATELY BUT GRADUALLY ! VERY DENSE LAYERS MAY BE LOOSENED OR WEAKENED BY BLAST BUT OVERALL EFFECT IS POSITIVE. REPEATED SHOTS ARE MORE EFFECTIVE THAN A SINGLE LARGE ONE OR SEVERAL SMALL ONES DETONATED SIMULTANEOUSLY. DELAYED BLASTING (1-5 SEC) IS MORE EFFECTIVE THAN ORDINARY BLASTING. WHEN A SERIES OF COVERAGES ARE USED THE SURFACE SETTLEMENT ACCOMPANYINGEACH COVERAGE IS USUALLY LESS THAN THE ONE PROCEEDING.

  46. CE-464 Ground Improvement DEPTH SHOULD BE GREATER THAN R IF SURFACE CRATERING IS TO BE AVOIDED. MOST WIDELY USED EXPLOSIVES ARE 60 % DYNAMITE, 30% SPECIAL GELATINE DYNAMITE AND AMMONITE. USING EXPLOSIVES FOR COMPACTION RELATIVE DENSITIES DR OF LOOSE SAND LAYERS CAN BE IMPROVED BY AN AVERAGE OF DDr = 15% UP TO 30% IF INITIAL DENSITY IS LOW ENOUGH (E.G. Dr<50%). FOR MEDIUM DENSITIES WHICH SURPASS FOR INSTANCE Dr = 60 % A NOTICABLE IMPROVEMENT IS OFTEN VERY DIFFICULT.

  47. HYDRO-BLASTING TECHNIQUE HAS BEEN USED VERY SUCCESFULLY INUSSR IN LOESS DEPOSITS (COLLAPSIBLE) • THERE ARE MAINLY TWO PROBLEMS ASSOCIATED WITH BLASTING. • EFFECTS ON ADJACENT STRUCTURES • EFFECTS ON PEOPLE CE-464 Ground Improvement

  48. CE-464 Ground Improvement

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