SOIL IMPROVEMENT METHODS
| Summary of Soil Improvement Methods | |||||||||
| In-Situ Deep Compaction of Cohesionless Soils | Method | Principle | Most Suitable Soil Conditions/ Types | Maximum Effective Treatment Depth | Special Materials Required | Special Equipment Required | Properties of Treated Material | Special Advantages and Limitation | Relative Cost |
| Blasting | Shock waves and vibrations cause liquefaction and displacement with settlement to higher density | Saturated, clean sands: partly saturated sands and silts (collapsible loess) after flooding | >30 m | Explosives, backfill to plug drill holes, hole casings | Jetting or drilling machine | Can obtain relative densities to 70-80, may get variable density strength gain | Rapid, inexpensive, can treat any size areas: variable properties, no improvement near surface, dangerous | Low | |
| Vibratory Probe | Densification by vibration; liquefaction induced settlement under overburden | Saturated or dry clean sand | 20 m (Ineffective above 3-4m depth) | None | Vibratory pile driver and 750 mm dia open steel pipe | Can obtain relative densities of up to 80. Ineffective in some sands | Rapid, simple, good underwater, soft under layers may damp vibrations, difficult to penetrate, stiff over layers, not good in partly saturated soils | Moderate | |
| Vibro-compaction | Densification by vibration and compaction of backfill material | Cohesionless soils with less than 20 fines | 30 m | Granular backfill, water supply | Vibroflot, crane, pumps | Can obtain high relative densities, good uniformity | Useful in saturated and partly saturated soils, uniformity | Moderate | |
| In-Situ Deep compaction of Cohesionless Soils | Compaction piles | Densification by displacement of pile volume and by vibration during driving | Loose sandy soils: partly saturated clayey soils, loess | >20 m | Pile material (often sand or soil plus cement mixture) | Pile driver, special sand pile equipment | Can obtain high densities, good uniformity | Useful in soils with fines, uniform compaction, easy to check results, slow, limited improvement in upper 1-2 m | Moderate to high |
| Heavy tamping (Dynamic compaction/consolidation) | Repeated application of high intensity impacts at surface | Cohesionless soils, waste fills, partly saturated soils | 30 m | None | Tampers of up to 200 tonne, high capacity crane | Can obtain good improvement and reasonable uniformity | Simple, rapid, suitable for some soils with fines; usable above and below water, requires control, shall be away from existing structures | Low | |
PART 6 STRUCTURAL DESIGN — SECTION 2 SOILS AND FOUNDATIONS
ANNEX K—(Continued)
| Method | Principle | Most Suitable Soil Conditions/Types | Maximum Effective Treatment Depth | Special Materials Required | Special Equipment Required | Properties of Treated Material | Special Advantages and Limitation | Relative Cost | |
| Injection and Grouting | Particulate grouting | Penetration grouting-fill soil pores with soil, cement, and/or clay | Medium to coarse sand and gravel | Unlimited | Grout, water | Mixers, tanks, pumps, hoses | Impervious, high strength with cement grout, eliminate liquefaction danger | Low cost grouts, high strength; limited to coarse-grained soils, hard to evaluate | Lowest of the grout systems |
| Chemical grouting | Solution of two or more chemicals react in soil pores to form a gel or a solid precipitate | Medium silts and coarser | Unlimited | Grout, water | Mixers, tanks, pumps, hoses | Impervious, high strength with cement grout, eliminate liquefaction danger | Low viscosity controllable gel time, good water shut-off; high cost, hard to evaluate | High to very high | |
| Pressure injected lime | Lime slurry injected to shallow depths under high pressure | Expansive clays | Unlimited, but 2-3 m usual | Lime, water surfactant | Slurry tanks, agitators, pumps, hoses | Lime in capsulated zones formed by channels resulting from cracks, root holes, hydraulic fracture | Only effective in narrow range of soil conditions | Competitive with other solutions to expansive soil problems | |
| Displacements grout | Highly viscous grout acts as radical hydraulic jack when pumped in under high pressure | Soft, fine-grained soils; foundation soils with large voids or cavities | Unlimited, but a few metre usual | Soil, cement water | Batching equipment, high pressure pumps, hoses | Grout bulbs within compressed soil matrix | Good for correction of differential settlements, filling large voids; careful control required | Low material high injection | |
| Electro-kinetic injection | Stabilization chemicals moved into soil by electro-osmosis or colloids into pores by electrophoresis | Saturated silts; silty clays (clean sands in case of colloid injection) | Unknown | Chemicals stabilizer colloidal void fillers | d.c. power supply, anodes, cathodes | Increased strength, reduced compressibility reduced liquefaction potential | Existing soil and structures not subjected to high pressures; not good in soils with high conductivity | Expansive | |
| Jet grouting | High speed jets at depth excavate, inject, and mix stabilizer with soil to form columns or panels | Sands, silts, clays | — | Water, stabilizing chemicals | Special jet nozzle, pumps, pipes and hoses | Solidified columns and walls | Useful in soils that can’t be permeation grouted, precision in locating treated zones | — |
ANNEX K—(Continued)
| Method | Principle | Most Suitable Soil Conditions/Types | Maximum Effective Treatment Depth | Special Materials Required | Special Equipment Required | Properties of Treated Material | Special Advantages and Limitation | Relative Cost | |
| Precompression | Preloading with/without drain | Load is applied sufficiently in advance of construction so that compression of soft soils is completed prior to development of the site | Normally consolidated soft clays, silts, organic deposits, completed sanitary landfills | — | Earth fill or other material for loading the site; sand or gravel for drainage blanket | Earth moving equipment, large water tanks or vacuum drainage systems sometimes used; settlement markers, piezometers | Reduced water content and void ratio, increased strength | Easy, theory well developed, uniformity; requires long time (vertical drains can be used to reduce consolidation time) | Low (moderate, if vertical drains are required) |
| Surcharge fills | Fill in excess of that required permanently is applied to achieve a given amount of settlement in a shorter time; excess fill then removed | Normally consolidated soft clays, silts, organic deposits, completed sanitary landfills | — | Earth fill or other material for loading the site; sand or gravel for drainage blanket | Earth moving equipment; settlement markers, piezometers | Reduced water content, void ratio and compressibility increased strength | Faster than preloading without surcharge, theory well developed, extra material handling; can use vertical drains to reduce consolidation time | Moderate | |
| Electro-osmosis | d.c. current causes water flow from anode towards cathode where it is removed | Normally consolidated silts and silty clays | — | Anodes (usually rebars or aluminium) cathodes (well points or rebars) | d.c. power supply, wiring, metering systems | Reduced water content and compressibility, increased strength, electrochemical hardening | No fill loading required, can be used in confined area, relatively fast; non-uniform properties between electrodes; not good in highly conductive soils | High |
PART 6 STRUCTURAL DESIGN — SECTION 2 SOILS AND FOUNDATIONS
ANNEX K—(Continued)
| Method | Principle | Most Suitable Soil Conditions/ Types | Maximum Effective Treatment Depth | Special Materials Required | Special Equipment Required | Properties of Treated Material | Special Advantages and Limitation | Relative Cost | |
| Admixtures | Remove and replace | Foundation soil excavated, improved by drying or admixture, and re-compacted | Inorganic soils | 10 m | Admixture stabilizers | Excavating, mixing and compaction equipment, dewatering system | Increased strength and stiffness, reduced compressibility | Uniform, controlled foundation soil when replaced; may require large area dewatering | High |
| Structural fills | Structural fill distributes loads to underlying soft soils | Use over soft clays or organic soils, marsh deposits | — | Sand, gravel fly ash, bottom ash, slag, expanded aggregate, clam shell or oyster shell, incinerator ash | Mixing and compaction equipment | Soft subgrade protected by structural load-bearing fill | High strength, good load distribution to underlying soft soils | Low to high | |
| Mix-in-place piles and walls | Lime cement or asphalt introduced through rotating auger or special in-place mixer | All soft or loose inorganic soils | >20 m | Cement lime asphalt, or chemical stabilizer | Drill rig, rotary cutting and mixing head, additive proportioning equipment | Solidified soil piles for walls of relatively high strength | Use native soil, reduced lateral support requirements during excavation; difficult quality control | Moderate to high | |
| Thermal | Heating | Drying at low temperatures; alteration of clays at intermediate temperatures (400-600°C); fusion at high temperatures (>1 000°C) | Fine-grained soils, especially partly saturated clays and silts, loess | 15 m | Fuel | Fuel tanks, burners, blowers | Reduced water content, plasticity, water sensitivity; increased strength | Can obtain irreversible improvements in properties; can introduce stabilizers with hot gases | High |
| Freezing | Freeze soft, wet ground to increase its strength stiffness | All soils | Several metre | Refrigerant | Refrigeration system | Increased strength and stiffness, reduced permeability | No good in flowing ground water, temporary | High |
ANNEX K—(Concluded)
| Method | Principle | Most Suitable Soil Conditions/Types | Maximum Effective Treatment Depth | Special Materials Required | Special Equipment Required | Properties of Treated Material | Special Advantages and Limitation | Relative Cost | |
| Reinforcement | Vibro replacement sand/stone columns | Hole jetted into soft, fine-grained soil and backfilled with densely compacted gravel or sand | Soft clays and alluvial deposits | 20 m | Gravel or crushed rock backfill | Vibroflot, crane or vibrocat, water | Increased bearing capacity, reduced settlement | Faster than precompression, avoids dewatering required for remove and replace; limited bearing capacity | Moderate to high |
| Root piles, soils nailing | Inclusions used to carry tension, shear, compression | All soils | — | Reinforcing bars, cement grout | Drilling and grouting equipment | Reinforced zone behaves as a coherent mass | In-situ reinforcement for soils that can’t be grouted or mixed in-place with admixtures | Moderate to high | |
| Strips and membranes | Horizontal tensile strips, membranes buried in soil under embankments, gravel base courses and footings | All soils | Can construct earth structures to heights of several metres | Metal or plastic strips, geotextiles | Excavating, earth handling, and compaction equipment | Self-supporting earth structures, increased bearing capacity, reduced deformations | Economical, earth structures coherent, can tolerate deformations; increased allowable bearing pressure | Low to moderate |
LIST OF STANDARDS
The following list records those standards which are acceptable as ‘good practice’ and ‘accepted standards’ in the fulfillment of the requirements of the Code. The latest version of a standard shall be adopted at the time of enforcement of the Code. The standards listed may be used by the Authority for conformance with the requirements of the referred clauses in the Code.
In the following list, the number appearing in the first column within parentheses indicates the number of reference in this Section.
IS No. Title
(1) 1892:1979 Code of practice for subsurface investigation for foundation (first revision) 2131:1981 Method of standard penetration test for soils (first revision)
2132: 1986 Code of practice for thin walled tube sampling of soils (second revision)
4434:1978 Code of practice for in-situ vane shear test for soils (first revision) 4968 Method for subsurface sounding for soils
(Part 1): 1976 Dynamic method using 50 mm cone without bentonite slurry (first revision)
(Part 2): 1976 Dynamic method using cone and bentonite slurry (first revision)
(Part 3): 1976 Static cone penetration test (first revision)
8763 : 1978 Guide for undisturbed sampling of sands and sandy soils
9214:1979 Method for determination of modulus of subgrade reaction (k-value) of soils in the field
(2) 1892:1979 Code of practice for subsurface investigation for foundation (first revision)
(3) 10042:1981 Code of practice for site-investigations for foundation in gravel boulder deposits
(4) 13365 Guidelines for quantitative classification systems of rock mass: Part 1 RMR for predicting of engineering properties (Part 1): 1998
(5) 2720 Methods of tests for soils (Part 1): 1983 Preparation of dry soil samples for various tests (second revision)
(Part 2): 1973 Determination of water content (second revision)
(Part 3/Sec 1): Determination of specific gravity, Section 1 Fine 1980
IS No. Title grained soils (first revision)
(Part 3/Sec 2): Determination of specific gravity, Section 2 Fine, medium and coarse grained soils (first revision) 1980
(Part 4): 1985 Grain size analysis (second revision)
(Part 5): 1985 Determination of liquid and plastic limits (second revision)
(Part 10): 1991 Determination of unconfined compressive strength (second revision)
(Part 11): 1993 Determination of the shear strength parameters of a specimen tested in unconsolidated undrained triaxial compression without the measurement of pore water pressure(first revision)
(Part 12): 1981 Determination of shear strength parameters of soil from consolidated undrained triaxial compression test with measurement of pore water pressure (first revision)
(Part 13):1986 Direct shear test (second revision)
(Part 15): 1986 Determination of consolidation properties (first revision)
(Part 28): 1974 Determination of dry density of soils in place, by the sand replacement method (first revision)
(Part 29): 1975 Determination of dry density of soils in place, by the core cutter method (first revision)
(Part 33): 1971 Determination of the density in-place by the ring and water replacement method
(Part 34): 1972 Determination of density of soils in-place by rubber-balloon method
(Part 39/Sec 1): Direct shear test for soils containing gravel, Section 1 Laboratory test
(6) 1498:1970 Classification and identification of soils for general engineering purposes (first revision)
(7) 401:2001 Code of practice for preservation of timber (fourth revision)
PART 6 STRUCTURAL DESIGN — SECTION 2 SOILS AND FOUNDATIONS
| IS No. | Title | IS No. | Title | ||
| (8) | 15180:2002 | Guidelines for use in prediction of subsidence and associated parameters in coal mines having nearly horizontal single seam workings | (Part 2):1976 | Dynamic method using cone and bentonite slurry (first revision) | |
| (Part 3):1976 | Static cone penetration test (first revision) | ||||
| (9) | 3764:1992 | Code of safety for excavation work (first revision) | (22) | 2131:1981 | Method for standard penetration test for soils (first revision) |
| (10) | 1904:1986 | Code of practice for design and construction of foundations in soils: General requirements (third revision) | (23) | 2911 | Code of practice for design and construction of pile foundations |
| (11) | 6403:1981 | Code of practice for determination of bearing capacity of shallow foundations (first revision) | (Part 1/Sec 1):2010 | Concrete piles, Section 1 Driven cast in-situ concrete piles (second revision) | |
| (Part 1/Sec 2):2010 | Concrete piles, Section 2 Bored cast in-situ concrete piles (second revision) | ||||
| (12) | 1888:1982 | Method of load tests on soils (second revision) | |||
| (13) | 8009 (Part 1):1976 | Code of practice for calculation of settlement of foundations: Part 1 Shallow foundations subjected to symmetrical static vertical loads | (24) | 14893:2001 | Guidelines for non-destructive integrity testing of piles |
| (25) | 2911 (Part 1/Sec 3):2010 | Code of practice for design and construction of pile foundations: Part 1 Concrete piles, Section 3 Precast driven concrete piles (second revision) | |||
| (14) | 12070:1987 | Code of practice for design and construction of shallow foundations on rocks | |||
| (15) | 1080:1985 | Code of practice for design and construction of shallow foundations in soils (other than raft, ring and shell) (second revision) | (26) | 2911 (Part 1/Sec 4):2010 | Code of practice for design and construction of pile foundations: Part 1 Concrete piles, Section 4 Precast concrete piles in prebored holes (first revision) |
| (16) | 11089:1984 | Code of practice for design and construction of ring foundations | (27) | 2911 (Part 3):1980 | Code of practice for design and construction of pile foundations: Part 3 Under-reamed pile foundation (first revision) |
| (17) | 9456:1980 | Code of practice for design and construction of conical and hyperbolic paraboloidal types of shell foundations | (28) | 2911 (Part 2):1980 | Code of practice for design and construction of pile foundations: Part 2 Timber piles (first revision) |
| (18) | 2974 (Part 1):1982 | Code of practice for design and construction of machine foundations: Part 1 Foundations for reciprocating type machines (second revision) | (29) | 2974 | Code of practice for design and construction of machine foundation |
| (19) | 2911 (Part 4):2013 | Design and construction of pile foundations — Code of practice: Part 4 Load test on piles (second revision) | (Part 1):1982 | Foundations for reciprocating type machine (second revision) | |
| (20) | 14593:1998 | Design and construction of bored cast in-situ piles founded on rocks — Guidelines | (Part 2):1980 | Foundations for impact type machines (hammer foundations) (first revision) | |
| (21) | 4968 | Method for subsurface sounding for soils: | (Part 3):1992 | Foundations for rotary type machines (medium and high frequency) (second revision) | |
| (Part 1):1976 | Dynamic method using 50 mm cone without bentonite slurry (first revision) | (Part 4):1979 | Foundations for rotary type machines of low frequency (first revision) |
| IS No. | Title | IS No. | Title |
| (Part 5):1987 | Foundations for impact machines other than hammers (forging and stamping press; pig breakers, drop crusher andjetter) (first revision) | 14293:1995 | Geotextiles — Method of test |
| 14294:1995 | Geotextiles — Method fordetermination of apparent opening size by dry sieving technique | ||
| 13301:1992 | Guidelines for vibration isolation for machine foundations | 14324:1995 | Geotextiles – Methods of test for determination of water permeability-permittivity |
| 9556:1980 | Code of practice for design and construction of diaphragm walls | 14706:1999 | Geotextiles — Sampling and preparation of test specimens |
| 14714:1999 | Geotextiles — Determination of abrasion resistance | ||
| (30) 13094:1992 | Guidelines for selection of ground improvement techniques for foundation in weak soils | 14715:2000 | Woven jute geotextiles — Specification |
| 14716:1999 | Geotextiles — Determination of mass per unit area | ||
| (31) 15284 (Part 1):2003 | Design and construction for ground improvement — Guidelines: Part 1 Stone columns | 14739:1999 | Geotextiles — Methods for determination of creep |
| 14986:2001 | Guidelines for application of jute geo-grid for rain water erosion control in road and railway embankments and hill slopes | ||
| (32) 15284 (Part 2):2004 | Design and construction for ground improvement — Guidelines: Part 2 Preconsolidation using vertical drains | 15060:2001 | Geotextiles — Tensile test for joints/seams by wide width method |
| (33) 13162 (Part 2):1991 | Geotextiles – Methods of test: Part 2 Determination of resistance to exposure of ultraviolet light and water (Xenon arc type apparatus) | (34) 2720 (Part 11):1993 | Methods of tests for soils |
| Determination of the shear strength parameters of a specimen tested in unconsolidated undrained triaxial compression without the measurement of pore water pressure (first revision) | |||
| 13321 (Part 1):1992 | Glossary of terms for geo-synthetics: Part 1 Terms used in materials and properties | ||
| 13325:1992 | Method of test for the determination of tensile properties of extruded polymer geogrids using the wide strip | (Part 12):1981 | Determination of shear strength parameters of soil from consolidated undrained triaxial compression test with measurement of pore water pressure (first revision) |
| 13326 (Part 1):1992 | Method of test for the evaluation of interface friction between geosynthetics and soil: Part 1 Modified direct shear technique | (35)9214:1979 | Method of determination of subgrade reaction (K value) of soils in the |
PART 6 STRUCTURAL DESIGN — SECTION 2 SOILS AND FOUNDATIONS
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PART 6 STRUCTURAL DESIGN
Section 3 Timber and Bamboo: 3A Timber
BUREAU OF INDIAN STANDARDS
- FOREWORD
- ... 3
- 1 SCOPE
- ... 5
- 2 TERMINOLOGY
- ... 5
- 3 SYMBOLS
- ... 7
- 4 MATERIALS
- ... 8
- 5 PERMISSIBLE STRESSES
- ... 19
- 6 DESIGN CONSIDERATIONS
- ... 20
- 7 DESIGN OF COMMON STEEL WIRE NAIL JOINTS
- ... 25
- 8 DESIGN OF NAIL LAMINATED TIMBER BEAMS
- ... 30
- 9 DESIGN OF BOLTED CONSTRUCTION JOINTS
- ... 32
- 10 DESIGN OF TIMBER CONNECTOR JOINTS
- ... 34
- 11 GLUED LAMINATED CONSTRUCTION
- ... 37
- 12 LAMINATED VENEER LUMBER
- ... 40
- 13 GLUED FINGER JOINTS
- ... 41
- 14 STRUCTURAL USE OF PLYWOOD
- ... 42
- 15 TRUSSED RAFTER
- ... 42
- 16 STRUCTURAL SANDWICHES
- ... 45
- 17 LAMELLA ROOFING
- ... 47
- 18 NAIL AND SCREW HOLDING POWER OF TIMBER
- ... 53
- 19 PROTECTION AGAINST TERMITE ATTACK IN BUILDINGS
- ... 53
- LIST OF STANDARDS
- ... 56
National Building Code Sectional Committee, CED 46
This Code (Part 6/Subsection 3A) deals with the structural design aspect of timber structures. In this Subsection, the various species of Indian timber, classified into three groups depending on the structural properties influencing the design most, are included.
This Section was first published in 1970 which was subsequently revised in 1983 and 2005. In the 1983 version of the Code, timber was covered under Section 3 of Part 6 under the title ‘Wood’, which did not cover bamboo. In the last version of 2005, the scope of Section 3 was enlarged as Section 3 Timber and Bamboo, which was subdivided into Subsection 3A ‘Timber’ and Subsection 3B ‘Bamboo’. This Subsection pertains to 3A Timber.
In the first revision of 1983, provisions of this Subsection were updated and design of nailed laminated timber beams, were included and information on bolted construction joints was added. In the second revision of 2005, a number of terminologies related to timber for structural purpose were added, strength data of additional species of timber were included, requirements for structural timber and preferred cut sizes thereof were modified, requirements for glued laminated construction and finger joints and also for laminated veneer lumber were introduced. Brief details were included for structural sandwiches, glued laminated beams, lamella roofing, nail and screw holding power of timber, structural use of plywood and trussed rafter. Further, guidelines for protection against termite attack in buildings were also incorporated in the last revision of this Subsection. Also, keeping into consideration the dwindling forest resources, brief details on use of plantation timbers including certain fast growing species and suitable guidelines in terms of their seasoning, sawing, treatment, etc and also use of finger jointing and glued laminated timber was introduced in the last revision so as to effect judicious use of timber.
As a result of experience gained in implementation of 2005 version of this Code and feedback received as well as formulation of new standards in the field and revision/ updation of some of the existing standards, a need to revise this Subsection was felt. This revision has, therefore, been brought out to take care of these aspects.
The significant changes incorporated in this revision include the following:
a) Definitions of various terms have been modified as per the prevailing engineering practice and new terminologies relating to timber for structural use have been added.
b) The permissible lateral strength (in double shear) of mild steel common wire for different new species of timber have been added and also strength values for some of the existing species have been modified based on latest research.
c) Guidance on increase in permissible lateral strength for mild steel nails clenched across the grains over nails with points cut flush, has been included.
d) Design provisions for timber connector joints have been further updated.
e) Data on block shear test results of glued timber joints based on the indigenous work, has been included.
f) Data on strength properties of glued finger joints based on the indigenous work, has been included for information and guidance in design.
g) A new figure has been added for possible orientation of planks in glue laminated beams (Glulam). Also, design outline for horizontally laminated beams has been added.
h) Design provisions for trussed rafters have been further updated and also some design data on the lateral load bearing strength of common wire nails in plywood-to-wood joints have been included for guidance in design.
j) Design provisions for lamella roofing have been updated and detailed.
k) Composite nail and screw holding power of some Indian timbers has been provided for guidance in design.
m) Reference to all the concerned Indian Standards have been updated.
PART 6 STRUCTURAL DESIGN — SECTION 3 TIMBER AND BAMBOO: 3A TIMBER
The information contained in this Subsection is largely based on the following Indian Standards:
IS 399 : 1963 Classification of commercial timbers and their zonal distribution (revised)
IS 883 : 2016 Code of practice for design of structural timber in building (fifth revision)
IS 1150 : 2000 Trade names and abbreviated symbols for timber species (third revision)
IS 2366 : 1983 Code of practice for nail-jointed timber construction (first revision)
IS 4891 : 1988 Specification for preferred cut sizes of structural timber (first revision)
IS 4983 : 1968 Code of practice for design and construction of nailed laminated timber beams
IS 11096 : 1984 Code of practice for design and construction of bolt-jointed timber construction
IS 14616 : 1999 Specification for laminated veneer lumber
All standards, whether given herein above or cross-referred to in the main text of this Subsection, are subject to revision. The parties to agreement based on this Subsection are encouraged to investigate the possibility of applying the most recent editions of the standards.
For the purpose of deciding whether a particular requirement of this Subsection is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded off value should be the same as that of the specified value in this Subsection.