Soil replacement

Soil replacement techniques are used to improve the strength of the soil and to reduce settlements resulting from future loading conditions. Soil replacement methods derive their improvement effects from a total removal and replacement of the existing soil or a combination of soil displacement and reinforcement through the insertion of granular material (see Moseley et al, 2004). The methods described below classify as soil replacement techniques and will be discussed in the following sections  

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Backfill the soil replaced over the pipe in the trench (general connotation). In cathodic protection, special backfills are packed around the anodes. These backfills are selected to lower circuit resistance of the anode for sacrificial anodes a gypsum/bentonite mixture is used, and for impressed-current anodes, coke breeze. 

Kobayashi E, Suwazono Y, Honda R, Dochi M, Nishijo M, KidoT, Nakagawa H. Serial changes in urinary cadmium concentrations and degree of renal tubular injury after soil replacement in cadmium-polluted rice paddies.Toxicol Lett. 2007 Nov 1. 

Leaves shrivel and turn brown. Cause Barberry wilt. This soilborne fungus attacks water-conducting tissue, causing leaves to wilt and eventually killing the entire plant. Remove the whole affected plant and its surrounding soil replace with fresh soil. 

Static traps were prepared by coating about 1 cm of the end of 358 C Curie-point pyrolysis wires with finely powdered activated charcoal. After being precleaned by being heated to the Curie point under vacuum, the traps were transported to the field test site in sealed culture tubes. At the field test site (a site known for ground-water contamination by tetrachloroethylene (PCE)), the static traps were placed in 25- to 35-cm-deep holes, covered with inverted aluminum cans, and the soil replaced in the holes. After 3 days the traps were removed for analysis. 

Once the mine is worked out and coal recovery operations cease, mined out areas are to be converted into productive agricultural land or restored to their former natural beauty. Potential recovery work is comprised of top-soil and sub-soil replacement, compaction, regrading, revegetation of the land, and chemical treatment and management of contaminated water resources. Recultivation necessitates the enrichment of soil for seeding and planting. Generally, land restoration reduces the potential for land destruction and pollution hazards. 

If soil lead levels exceed 1000 ppm, avoid leafy and root crops, and either dilute the top 6 inches of soil with new uncontaminated soil or plant in containers, or raised beds lined with plastic, with the top 6 inches of soil replaced with clean topsoil. If the soil has over 3000 ppm lead, no planting of edible crops should be considered. ... 

An important aspect of soil replacement, and often a limiting factor, is the need for transport and disposal of the removed material. If the soil caimot be recycled as a construction material in the fill itself or disposed of at a nearby location, the eosts of removal can be significant, especially if the soil is contaminated. In these eases other soil improvement techniques, which immobihse or stabilise contaminants in the soil, may be more economical. 

Another soil replacement method uses Geotextile Encased sand Columns (GEC). These columns can be installed in very soft soils. They can accelerate the consolidation process, increase the shear strength and reduce the settlements of soft subsoil. 

Determine the acceptability of these deformations or the need for soil improvement by comparing the predicted deformations with the relevant performance requirements. Soil improvement could include a surcharge and vertical drains to accelerate the consolidation process, compaction of the granular fill or soil replacement (see Chapter 7). 

Soil improvement Increase the shear strength in situ by soil replacement/improve-ment Accelerated consolidation by means of the installation of vertical drains. 

Soil replacement can be realised just at the toe of a slope in order to obtain a larger soil (counter) weight (Figure 8.32). The effect of increased shear strength at this location is, however, limited because of the relatively small effective vertical stresses. 

Alternatively (or in combination with the above), soil replacement is realised underneath the entire slope and the crest. The effect of the increase in shear strength is, in this case, more significant and potential slip surfaces will be pushed backwards resulting in a deeper and less critical failure mechanism. 

In this section, general descriptions of the principles involved in ground improvement methods, i.e., densification, solidification, drainage, reinforcement, containment, and soil replacement, as well as some representative methods, are presented. Verification techniques and design issues associated with general ground improvement methods are also explained. 

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