HOW TO IMPROVE THE BEARING CAPACITY OF A WEAK SOIL

 

Building on made-up ground or fillings is a very commonly encountered condition by most of the practicing engineers. Many a time, the filling is done with cohesion-less soil, construction debris, cinders, solid waste from the locality, and not even allowed to have 1-2 seasons’ weathering before construction. The bearing capacity of a filled-up land depends on the nature of filling materials, its depth and degree of consolidation. In many cases, such information is either not available or wrongly stated by the owner. Unfortunately, this happens due to lack of awareness.

Very fine fills like fine sand, silt soil, clay, loosely placed and not properly compacted during filling, takes a very long time to get consolidated. Occasional rolling hardly makes any difference as with it only 20-30 cm layer from the top gets compacted. It is always suggested to dig a test pit in such a land, and to have an inspection of the sides to guess the extent of consolidation; here experience play a major role. However, the best and safest way to check the bearing capacity of the soil as per standard methods of soil test.

CARES DURING FILLING OF LAND:

At the time of filling up depressed patches, ponds or ditches, the following sequence is highly recommended:

·         Water stored in the ponds or depressions shall be pumped out.

·         The first layer shall preferably be a granular fill.

·         Filling layers shall not be more than 30-35 cm and shall be immediately consolidated.

·         Insertion of granular fill in between fine fills improves drainage condition.

·         In case of filling with clay, the top layer shall preferably be with granular fill.

FOLLOWINGS ARE USEFUL TO IMPROVE THE BEARING CAPACITY OF A WEAK SOIL

·        If the foundation trench is left open for one monsoon it will enable the foundation soil to settle down. It will also be possible to observe the nature of the natural movement of the soil due to influence of moisture.

·       Increasing the depth of foundation if oozing out water problem is not encountered badly.

·       Compacting the soil by ramming with broken brickbats, sand, cinder and moorum. This is a very useful and popular method.

·       Removing the weak soil patches and back filling with sand, rubble stone, gravel, brickbats etc. the hard fills are to be rammed hard and shall be totally embedded in the soil. Cement grouting of the rammed materials will make the foundation much harder.

·        Draining out of water from wet or waterlogged foundation.

·        Driving piles

·        Altering the choice of foundation system.

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Green Environment

Hi, I’m Gobinda Burman (Green Environment). More than 27 years in the field of Building Construction industry, I’ve completed many high-rise building projects successfully. I have got the opportunity to learn and solve the critical practical problems related to building construction. I love to share my knowledge with those people who wants to build their own home and the budding civil engineers willing to build their career in this field..

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