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Site foundation soils or project earth constructions are referred to as ground improvement or ground modification if they are altered to improve their performance under design and operational loading conditions.
When poor soil conditions are encountered, the ground repair is required. Instead of excavating and completely replacing the bad soil, it is frequently more cost-effective to merely apply some sort of treatment to the soil that is already there.
Subsurface characteristics that are adverse to a project may necessitate averting the site, altering the design of the proposed construction, eliminating and replacing unacceptable soils, or attempting to adapt the existing ground if possible.
Many projects' needs include improving geomaterials and geotechnical conditions.
Enhancement of the ground's carrying capacity and reducing settlement of soft ground is a common goal. Ground enhancement can also be used to avoid seismic liquefaction or to stabilize excavation bottoms.
Increasingly, road and rail embankment buildings are being constructed employing column-type ground enhancement techniques. Geotextile-encased columns (GEC) are also employed in the building of dike foundations.
These strategies aim to alleviate the pressure on soft soils without significantly affecting the structure of the soil. Geotextile or geogrid reinforcements are typically used to produce a load-transfer mat on top of a grid pattern created by placing column or pile-type structures into a bearing layer.
Arching in the embankment redistributes the stresses and stabilizes the geotextile/geogrid reinforcement, resulting in stress alleviation for the soft soils (membrane effect). Lower compressibility and enhanced bearing capacity and shear strength can be achieved as a result of the upgraded or composite ground.
An increasing number of designers are comparing the design of a foundation with a traditional pile (or pile raft) solution and the possibility of using soil mix elements covered by a load transfer platform made of granular material reinforced with geosynthetics during the design phase.
Although pile foundation design standards and recommendations abound, numerical modelling is often necessary to evaluate the combined solution's safety (the soil mix elements and the load transmission platform) due to a lack of basic information regulating the solution's behaviour.
When it comes to improving foundation soils, compaction grouting was deemed the best option since it doesn’t cause any vibratory motions, making it ideal for controlling foundation movement.
A low-mobility aggregate grout injected in phases through 100-mm diameter steel casings enhances soil through compaction grouting. Percussion hammer attachment of a drop-off conical tip to an inclined or vertical steel casing is required at each grout probe point.
At each stage, the grout volume and injection pressure are carefully monitored, while the steel casings are taken out by 0.3 to 0.6 metres at a time. Foundation heave is more common in compaction grouting than settlements, which are more common in vibratory densification.
When injecting grout less than 10 metres below ground level, pressure and volume are normally lowered to limit the heaving of the earth and adjoining foundations.
Compaction grouting was used to enhance the ground, and the process was carried out in phases as is customary. Primarily, a variety of primary injection sites were grouted before additional holes were grouted. Grouting began with the grouting of six principal holes in the foundation and two extra holes near the foundation's border.
The in-situ grout columns' diameter is extrapolated from the grout quantities injected and varied from 200 to 600 mm. A total of six days are normally needed to complete the grouting of these first holes (i.e. 8 x 24 linear m of grout column). Slow progress is mostly caused by a 24-meter casing penetration and significant grout usage.
In loose to compact sandy soils like those found at the cold box site, a production rate of 100 linear metres per day is considered typical. However, the tilt metres and the measured settlements were often tiny (less than 5 mm) throughout this phase of grouting.
When other approaches can't be employed because of restrictions in the subsurface, dynamic compaction is the go-to solution. It's a technique for increasing the mass of soil deposits by compacting them.
Dropping a heavy object repeatedly on the ground at regular intervals is what this technique entails. The more the weight and the greater the height, the greater the likelihood of compacting. In order to achieve the appropriate level of compaction, the weight employed is between 8 tonnes and 36 tonnes in weight. 1m to 30m is the height range.
Stress waves generated by the free fall's impact aid in soil densification. These stress waves can travel up to a distance of ten metres. These waves cause liquefaction in cohesionless soils, which is then followed by compaction, whereas in cohesive soils, they raise pore water pressure, which is then followed by compaction.
In geology, the pressure of water within the pores of rocks and soils is referred to as pore water pressure (PWP).
The weight of the hammer, the height of the hammer, and the spacing of the hammer drop all affect how compressed the material is after the impact. A higher depth of penetration can be achieved when the first weight is dropped.
The deeper layers are compacted first, and then the topsoil is compacted to seal in the new compacted material.”
A vibrator is used to construct highly compacted columns of gravel or similar material in poor soils to improve their structural integrity. All soils in the treatment zone are strengthened and neighbouring granular soils are deepened as a result of the displacement process.
Soil conditions that aren't optimum may be necessary because of space and timing restrictions in infrastructure buildings.
Soil conditions can be greatly improved thanks to the expertise of the geotechnical engineer. The kind of stratum and the goal of the improvement will determine the type of ground improvement technique used.
Ground renovation with stone columns is a proven and cost-effective method in a variety of situations. Make a stone column out of several compositions to see which one offers the earth greater sturdiness.
I hope this post provides you with a good understanding of the Ground Improvement Process, its objective and its methods. Please feel free to like, comment and share it.
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