Chapter 3 Improving Site Soils for Foundation Use
Chapter 3 Improving Site Soils for Foundation Use
3.1 Introduction This chapter will focus on several of the more widely used methods of improving soils for bearing capacity. ■ An extremely large number of methods have been used and /or reported in the literature. ■ At an individual site one may use a mix of several methods to achieve the desired result. Means to obtain a significant increase in the bearing capacity of a soil-can be achieved by altering the soil properties of cohesion c or density p
3.1 Introduction ▪ This chapter will focus on several of the more widely used methods of improving soils for bearing capacity. ▪ An extremely large number of methods have been used and /or reported in the literature. ▪ At an individual site one may use a mix of several methods to achieve the desired result. ▪ Means to obtain a significant increase in the bearing capacity of a soil-can be achieved by altering the soil properties of Φ,cohesion c or density ρ
Approaches to soil property modification Mechanical stabilization Compaction ■Preloading ■.Drainage Densification using vibratory equipment Use of the situ reinforcement-sometimes called composite ground ◆ Grouting Use of geotextiles Chemical stabilization
Approaches to soil property modification ▪ Mechanical stabilization ▪ Compaction ▪ Preloading ▪ Drainage ▪ Densification using vibratory equipment ▪ Use of the situ reinforcement-sometimes called composite ground ▪ Grouting ▪ Use of geotextiles ▪ Chemical stabilization
3.2 Lightweight and Structural Fills A method that allows construction of relatively light structures on very soft base soil is to use either a lightweight fill or a carefully placed structural fill onto which the foundation is placed. Lightweight fills may use expanded shale, certain industrial slags,and fly ash.These 淘 materials may be mixed with sand and/or gravel to produce a fill of the desired density and durability. EPS (expanded polystyrenc)fill can be used for embankment in highway engineering. 超
3.2 Lightweight and Structural Fills ▪ A method that allows construction of relatively light structures on very soft base soil is to use either a lightweight fill or a carefully placed structural fill onto which the foundation is placed. ▪ Lightweight fills may use expanded shale, certain industrial slags, and fly ash. These materials may be mixed with sand and/or gravel to produce a fill of the desired density and durability. ▪ EPS (expanded polystyrenc) fill can be used for embankment in highway engineering
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3.3 Compaction Compaction is economical method of improving the bearing capacity of site soils. It may be accomplished by excavating to some depth,then carefully backfilling in controlled lift thickness,each of which is compacted with the appropriate compaction equipment. The backfill soil may be the excavated soil dried (or wetted)as necessary,possibly mixed with an admixture such as cement or lime,with or without fly ash or sand filler;or it may be imported soil from a nearby borrow pit. 超
3.3 Compaction ▪ Compaction is economical method of improving the bearing capacity of site soils. ▪ It may be accomplished by excavating to some depth, then carefully backfilling in controlled lift thickness, each of which is compacted with the appropriate compaction equipment. ▪ The backfill soil may be the excavated soil dried (or wetted) as necessary, possibly mixed with an admixture such as cement or lime, with or without fly ash or sand filler; or it may be imported soil from a nearby borrow pit
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