CONSOLIDATION OF SOILS: TESTING AND EVALUATION

By F. LIMIO

AFTER COMPACTION DENSITY G/CC DEPTH (M) BEFORE COMPACTION SUBSURFACE 400 MM BEYOND A DEPTH 2 5 M THERE IS NO IMPROVEMENT FIGURE 1 2: GRAPHICAL REPRESENTATION OF IMPROVEMENT BY DROP HAMMER METHOD (B) HYDRAULIC MODIFICATION UNDER THIS METHOD, FREE PORE WATER IS FORCED OUT OF THE SOIL VIA DRAINS OR WELLS IN COURSE-GRAINED SOIL THIS IS ACHIEVED BY LOWERING THE GROUND WATER LEVEL THROUGH PUMPING FROM BOREHOLES, OR TRENCHES IN FINE-GRAINED SOILS THIS IS ACHIEVED BY THE LONG-TERM APPLICATION OF EXTERNAL LOADS (PRELOADING) OR ELECTRICAL FORCES (C) PHYSICAL AND CHEMICAL MODIFICATION STABILIZATION IS DONE BY PHYSICALLY MIXING SOME ADHESIVES WITH SURFACE LAYERS OR COLUMNS OF THE SOIL CONSOLIDATION OF SOILS: TESTING AND EVALUATION SURCHARGE SETTLEMENT TIME PRELOADING REDUCES SETTLEMENT WITH PRELOADING WITHOUT PRELOADING FIGURE 1 3: GROUND MODIFICATION BY PRELOADING THE ADHESIVE MATERIALS MAY INCLUDE NATURAL SOILS, INDUSTRIAL BY-PRODUCTS OR EVEN WASTE THE PROCESS OF INJECTING ADHESIVES VIA BOREHOLES UNDER PRESSURE INTO VOIDS WITHIN THE GROUND OR BETWEEN THE GROUND AND A STRUCTURE IS CALLED GROUTING SOIL STABILIZATION BY HEATING AND BY FREEZING THE GROUND IS CONSIDERED THERMAL METHODS OF MODIFICATIONS ALLUVIUM ROCK CURTAIN BELOW DAM GROUT GROUTING FOR SUBWAY EXCAVATION FIGURE 1 4: MODIFICATION BY GROUTING (D) MODIFICATION BY INCLUSIONS AND CONFINEMENT REINFORCEMENT BY FIBRES, STRIPS, BARS MESHES AND FABRICS IMPARTS TENSILE STRENGTH TO A CONSTRUCTED SOIL MASS CONSOLIDATION OF SOILS: TESTING AND EVALUATION IN-SITU REINFORCEMENT IS ACHIEVED BY NAILS AND ANCHORS STABLE EARTH RETAINING STRUCTURE CAN ALSO BE FORMED BY CONFINING SOIL WITH CONCRETE, STEEL, OR FABRIC ELEMENTS DAM PILLAR LOAD STRIP FIGURE 1 5: MODIFICATION BY REINFORCEMENT SUITABILITY, FEASIBILITY AND DESIRABILITY OF THE METHOD THE CHOICE OF A METHOD OF GROUND IMPROVEMENT FOR A PARTICULAR OBJECT WILL DEPEND ON THE FOLLOWING FACTORS NATURE AND THE EXTENT OF IMPROVEMENT REQUIRED THE TYPE OF SOIL, GEOLOGICAL STRUCTURE, SEEPAGE CONDITIONS PREVAILING AT THE SITE THE COST INVOLVED AVAILABILITY OF THE EQUIPMENT AND MATERIALS AND THE QUALITY OF WORK REQUIRED CONSTRUCTION TIME AVAILABLE POSSIBLE DAMAGE TO EXISTING STRUCTURES OR POLLUTION OF GROUNDWATER RESOURCES DURABILITY OF THE MATERIAL TO BE USED (AS AGAINST THE REQUIRED LIFE OF THE STRUCTURE TO BE BUILT FOR THE GIVEN ENVIRONMENTAL AND STRESS CONDITIONS) TOXICITY OR CORROSIVENESS OF ANY CHEMICAL ADDITIVES RELIABILITY OF THE METHOD OF ANALYSIS AND DESIGN FEASIBILITY OF THE CONSTRUCTION CONTROL AND PERFORMANCE MEASUREMENTS IF THE SOIL IS MOIST, THERE IS A POSSIBILITY OF FREEZING OF THE SOIL CONSOLIDATION OF SOILS: TESTING AND EVALUATION