Sometimes Mother Nature doesn’t provide the best soil at the construction site. Soil can be sandy, silt or clay, or any combination of the three, all layered upon each other like an onion. Each type of soil has different properties that influence the way that the ground must be prepared during the construction of buildings, bridges and other structures. In wet conditions, some types of soil can behave as a liquid during an earthquake, causing major structural damage to any buildings unfortunate enough to rest upon it.
Difficult and dangerous soil conditions can be mitigated by the skilled use of sophisticated ground improvement techniques. Ground improvement increases the load bearing capacity of the soil while decreasing the risk of settlement and liquefaction. Legacy Foundations’ team of certified experts can help alleviate troublesome soil and keep your construction project on track.
Each site will be analyzed to determine which type of ground improvement is best for the structure and the soil conditions that are particular to that site.
Dynamic compaction increases the density of a soil by repeatedly dropping a heavy weight on the surface. This method increases the load bearing capacity of the soil while decreasing the potential for settlement and liquefaction. In sinkhole-prone areas, dynamic compaction also has the benefit of reducing the probability of sinkholes by collapsing hidden voids prior to construction.
Vibro Replacement, or Stone Columns, uses a downhole vibrator to create dense aggregate columns via either a wet top feed or dry bottom feed process. The wet top feed process utilizes water at the tip of the vibrator to assist in driving down to the desired depth. The stone columns are then built from the bottom up by slightly raising the vibrator from the bottom of the shaft and adding crushed stone or recycled concrete at ground level. Once the stone fills the bottom of the shaft, the vibrator is then lowered again and the process is repeated until the stone column reaches the surface.
The dry bottom feed process uses a feed pipe attached at the tip of the vibrator to introduce the stone and create the column. Because this process does not use water to assist in reaching the desired depth, predrilling may be required.
Soil mixing is another cost efficient method of ground improvement, and consists of drilling into the soil and mixing it with a binding agent to create a cement-like column or rectangle beneath the soil surface.
Single axis, or deep soil mixing (DSM) consists of a single rod with mixing paddles that is used to create large columns of soil mixture at strategic locations on the construction site. Similarly, multi-axis soil mixing utilizes three counter rotating rods with mixing paddles, which can be used to create a continuous panel of subsurface support. Cutter Soil Mixing (CSM) uses counter rotating wheels rather than rods, and creates soil cement panels of varying widths, which is ideal for constructing walls. CSM has the additional advantage of being able to create a soil cement panel in difficult and rocky conditions, including directly into bedrock if required.
Tip Grouting, also known as Post Grouting, is the process where the completed drilled shaft is pre-loaded, allowing for grout to be inserted at the tip of the shaft, densifying the ground and enlarging the tip area. This creates improved shaft resistance and a redistribution of stresses along the shaft.