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the method of treatment of expansive and collapsing soils

1. for expansive soils

The following are description of treatment methods used by

Colorado DOT and other transportation agencies in alleviating

Detrimental volume change of expansive soils:

• Sub-excavation and removal of expansive soil and replacement with non-expansive soil

•Application of heavy applied load to balance the swelling

 Pressure

•Preventing access of .water to the soil by encapsulation

•stabilization by means of chemical admixtures

•Mechanical stabilization

•Explosive treatment to correct swelling shale’s

•Pre-wetting the soil

•Avoiding the expansive soil

•isolation of origin from expansive soil

•Flexible origin design

•Soil treatment to reduce biological changes

•Rainwater and drainage control

•- Precautions related to crops adjacent to the munch

1. Sub-Excavation and Removal of Expansive Soil and Replacement with Non-Expansive Soil.

Sub-excavation and replacement requires removal and replacement of the expansive subgrade soils. The material being put back should not cause problems with respect to the in situ material (1) . For example, granular soils should never be used as backfill for sUb-excavation and replacement projects. The use of granular materials encourages collection of water at the surface of the underlying in situ materials. In one case, on Interstate 70 east, between Watkins and Byers, the replacement consisted of 18 to 30 inches of sand. The performance of this treatment was noted as unsatisfactory

2. Application of Heavy Applied Pressures To Balance

The swelling Pressures

Loading the expansive soil with pressure greater than the swelling pressure is a method by which swelling can be prevented. However, pavement loads are generally insufficient to prevent expansion, and this method is usually applied in the case of large buildings or structures imposing high loads (3). The use of this method i n the highway construction is limited to swelling soils with low expansive pressures.

3. Stabilization By Means of Chemical Admixtures

Chemical admixtures have been used to alter the characteristics of clay mineral and reduce its potential for swelling. Lime is perhaps the most effective of all the chemicals used to stabilize the expansive soils. The major limitation of its routine use is the application of the chemical to sufficient depth (1). Conventional techniques generally limit the depth of treatment to approximately 8 to 12 inches. Lime stabilization can be applied using a variety of methods. Lime shaft and lime-tilled stabilization are the two methods used most by Colorado DOT. Attempts to distribute lime through natural soils with water in drill holes have not been proven successful, because the lime is only slightly soluble in water

4. Avoid the Expansive Soil

Avoiding the expansive soil in lieu of more favorable subgrade conditions is a viable alternative. However this is only applicable in limited situations, since route selection is generally based on local social, economic, environmental, or political considerations prevalent at this point in the design sequence

5. Isolation FROM EXPANSIVE SOIL

Here the origin is isolated and blocked from the effect of stresses (stressess) caused by stretching and shrinkage (SWELLING & SHRINKING) the surrounding soil, which is completely or partially replaced by the soil (REPLACEMNET), if shallow thickness is small, then it can be drilled, removed and replaced by a non-dilative fill, while if the bulge layer is deep, it is dug deep enough and then refilled with non-stretching, taking into account the speed of the filling to avoid deep soil dryness.

Swollen soils may also cause horizontal strerssess(HORIZONTAL) if they are limited to anchor structures such as basement walls or support walls (RETAINING_WALLS).

When constructing a large support wall to support bulidying soil, the soil is dug and removed behind the walls and then replaced with non-stretching soil (NONSWELLING) with the use of a waterproof membrane around the landfill, in order to avoid changing the moisture content of the landfill soil (SOIL_MOISTURE).

When drilling and replacement is possible, it is possible to solve the origin on cylindrical poles (PIERS) up to the non-stretch layer, in order to isolate the origin from the effect of unequal motion (UNEQUAL), and the cylindrical columns themselves are covered with a cylindrical casing of fiber (BOARD CIRCULAR) FORM, these columns are better than the use of piles, in order to avoid lifting and vibrations (HEAVE and VIBRATIONS) associated with the pottery.

Whether the cylindrical columns or the grooves are used, they must be carefully designed because the wrong design so as not to lead to cracks and collapses in the walkers.

Finally, it should be noted that the upward forces exerted by the bulging soil on these columns and the grooves at their maximum do not exceed the loads of this mayor (PICR LOAD) or the grooves, otherwise

 

There is a very effective way to treat the bulge of various soils called a mixture of soil depth

Invented in Japan and Scandinavia. Their use is constantly increasing in the world, both in enhancing soil insulation in soft or porous ground. And the method enables a significant improvement in the mechanical and physical properties of the treated soil.

And there are two ways of

1- Wet method: mechanically mixing the soil with cement additives or good milk

2. Dry method: Use high-pressure injections in clay additives to improve mixing quality.

. DSM technology is based on an innovative concept of improving natural soil l to reach specific properties to solve the problems of drilling collapses and avoid the use of deep foundations and in wide areas of application, as well as a wide range of engineering configurations that can be used for security and geotechnical solutions.

In case if the soil to be established has the properties of bulwarks, the dish is replaced with a suitable thickness with your blood this layer well up to 95 per cent and prefers to use clean sand and also prefers to work the basis system of separate rules and mid in order to be able to breathe soil... The perimeter of the building is also isolated and protected from the water as much as possible and a drainage system is well connected... These tools protect the foundations from the impact of the swelling of the soil in the event of water leaking down the foundations and are also inexpensive...... But it's not preferable that the facilities be flexible because they won't resist the bulge of the soil up, but the bases are tied to a high-body med.

 

 

2. for collapsing soils

1. Clear each collapse and retreat area and rebuild the landfill by implementing a retomo with coarse soil1

2. Clean, compressed in 0.3 meters thickness layers. With the completion of a drainage with a so-called granular mask. . (TVO)

3. Wall charger to keep dirt.

4. Wall charger reinforced concrete piles based anchored at depths exceeding 4 meters in the foundation.

5. Wall retain charger reinforced floor cladding added to

Geocomposite with the completion of water drains.

6- Use of soil additives, such as silica, gypsum and cement to improve the mechanical properties of natural soils

The best solution in my estimation is to use booster’s b (georgic, Geosynthetics)

With the completion of water drains to treat slippage and collapse and rebuild the landfill, this saves you time and reduces the pressure of the completion period compared to the traditional techniques of granular materials, because they provide greater guarantees of duty performance, in time, and profit in major drilling and flattening works.

To reduce the susceptibility of the soil to collapse there are many steps to follow, including:

7. Removal of the collapsed soil layer.

8. Reducing water access to the soil by creating a good drainage system and using modern methods of irrigating crops.

9. Use substrates to reach non-collapsible layers in the design of foundations.

10. Improve soil properties by adding chemicals to strengthen the bonding of their molecules increase their strength and change their physical properties.

11. Flood the soil with water before construction to reduce the amount of soil landing

12. Soil to get denser soil in different dk ways.

13. Remove the collapsed soil layer.

14. Condensation and destruction of the collapsed soil using various condensation methods such as shock anchors or vibrational catalytic sororities.

15. Replace the soil with a layer of clean sand with the blood in the case of highly collapsed soil.

16. Reducing water access to the soil by creating a good drainage system and using modern methods of irrigating crops.

17. Use the grooves to reach the non-collapsing layers taking into account the calculation of the value of negative friction on the grooves during their penetration into the collapsed soil layers.

18. Improving soil properties by adding chemicals to strengthen the bonding of their molecules increase their strength and change their physical properties

19. Flooding the soil with water before it is implemented.

20. The implementation and design of high-speed sympers to link separate rules.

21. In the case of the use of a pout, it must be high-speed to resist the uneven decline resulting from the collapse of the soil and preferably the use of cumin.

 

RESULTS AND DISCUSSION:

Based on the literature reviewed and the result of the survey Questionnaire received from the District Materials Engineers, the Following conclusions and recommendations are presented.

The use of DOH Memo No. 323 as a criterion to treat Swelling soil problems appear to be adequate for some Locations. However, its use is not recommended for very Dense sub grade such as the type in western Colorado. Granular soils alone should never be used as backfill for sub excavation and replacement projects. The use of granular Materials encourages collection of water at the surface of the Underlying in situ materials. However granular soils may be

Used in conjunction with a filter-separator layer and edge drain To collect and divert the water from the pavement structure. Catalytically blown asphalt membranes have been used

Successfully to minimize subgrade moisture variations in Colorado. Care should be taken to provide a smooth and uniform surface prior to placement of membrane.

Swelling bedded shale is the primary cause of pavement distress In the western slopes of Colorado (District III). A low-level Explosive is a viable alternative for disorienting the bedded

Shale and lowering its density similar to treatment by sub excavation and compaction. The cost of treating swelling shales using a low-level explosive was estimated to be one fifth of the cost of sub-excavation and recompaction. Blasting as a treatment technique for swelling shales requires careful drill patterns and precise charges.

CONCLUSIONS:

This research study has demonstrated that the performance of some of the swelling soil treatment methods used in Colorado has been poor. As a result, we recommend initiation of the second phase of this study. The ultimate goal of the second phase will be to over haul the existing guidelines and establish up-to-date design guidelines for highway construction on swelling soils and swelling shales in Colorado. For any specific treatment method, the laboratory and field personnel should be trained. The cost-effectiveness of each individual treatment method needs to be evaluated for a given condition. Environmental conditions and geologic formation should be given special attention in identifying and controlling the swelling problems.

 

 

REFERENCE:

 

Books:-

 

1. Lectures of Foundation Engineering& Soil mechanics: by DR. Wael Nashat Abdul-Sama'a, Egypt

 

2 - Fundamentals of Foundation Engineering& Soil mechanics part1: by Prof Dr. sayed Abdul Fattah Al-Kasabi, 1994, Egypt

 

3. Egyptian Code of Foundation Engineering& Soil mechanics

 

4. WWWEB Enhanced Foundation Engineering& Soil mechanics, AISC.

 

5. Fundamentals of Foundation Engineering& Soil mechanics part 1: by Prof Dr Osama Mustafa Al-Shafei egypt

6. Fundamentals of Foundation Engineering& Soil mechanics part1,part5: by Prof Dr. Emad Darwish, Egypt