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Pressure Grouting
Pressure Grouting is considered to be the best remediation design and process for the repair of sinkholes. Pressure Grouting can be broken down into what NEC Keystone calls the 3 phases.

Phase 1 – Rotary Wash Drilling

Making sure that the grout injection pipe enters the Karst (weathered or fractured limestone) zone.

Phase 2 – Sealing off the Karst

Using high pressure grouting to seal off the areas of fracture or deterioration in the limestone.

Phase 3 – Consolidation/Compaction

This phase includes the replacement of lost materials and the consolidation/compaction of soil zones above the karst formations.

Phase 1 – Rotary Wash Drilling

It was NEC Keystone that introduced the technology of Rotary Wash Drilling which is now the only accepted standard for installation of grout casing for sinkhole remediation. Prior to NEC Keystone’s entry into the foundation repair arena the standard for installation of grout injection pipe for sinkhole remediation was auger drilling followed by manually dropping pipe/casing into the excavation. The problem with this technology was that in most cases the grout injection points did not achieve proper depth to reach the karst activity zone in order to seal the karst damage. If you do not seal off and repair the karst area the remediation process will not be effective due to future continued soil movement through the still existing karst fractures. During the drilling process we monitor the pressure and return from our drills. These 2 factors indicate when our injection pipe has reached the fractured karst are. It is important to remember that if a contractor has not properly drilled into the karst no repair will take place to the karst itself.

The NEC Keystone difference:

1. NEC Keystone has a dedicated trailer system that mixes the appropriate drilling fluids and delivers them to the drill in an environmentally friendly way. 2. All returned drilling material and cuttings (sand, dirt, water, etc.) is returned back to the drilling trailer to be recycled and used again. This is good both for the environment and the cleanliness of the project.

Phase 2 – Sealing off the Karst

Phase 2 in the compaction grouting process is sealing off and repairing the karst area. It is vital to the repair process that the karst area is correctly sealed off and repaired. NEC Keystone achieves this high level of repair by using the correct technology by our highly trained crews during the installation of the grout injection pipe in Phase 1. By then monitoring the pressures coming from the grout pump we can be assured that the karst has been properly sealed. When increased pressure is achieved (normally 250-300 PSI over static line pressure) you can be certain that the karst area has been remediated. NEC Keystone only purchases grout material from certified, independent grout suppliers such as Cemex and B.E.T.-ER Mix. We do this to insure the highest quality product for your project as well as independent verification of quality, times and amounts.

Phase 3 – Consolidation/Compaction

Once the karst has been repaired, consolidation and compaction becomes the final critical step of the pressure grouting procedure. During this phase two types of repair are being completed: 1. Replacing all the material that has migrated through the karst zone. 2. Consolidating and compacting the loose soils in all the soil zones above the karst area using medium to high pressure injected grout material to compact the surrounding areas. During this phase of the procedure the grouting terminates between 10 and 20 feet below grade depending on your engineering firms specifications. It takes highly trained and skilled remediation specialists, from the foreman to the crews, in order to complete the grouting repair program. All 3 Phases of the compaction grouting remediation process are equally important. If all 3 of the Phases are not completed properly the remediation procedure is not successful. If the Rotary Wash Drilling is not completed properly in Phase 1 the karst area cannot be sealed off and remediated. If the karst area is not sealed correctly in Phase 2 the compaction process will not be successful and the structure will continue to settle.

The NEC Keystone difference:

We have historically introduced all the newest technologies into the sinkhole industry including the use of Rotary Wash Drilling as well as the use of low pressure hydraulic systems for safely removing grout injection pipes. We purchase all of our grout material from certified vendors to insure the quality of the materials being used on your project. We use our own specially created drill trailers to recycle our drilling fluid for a smaller footprint on the environment. All of our drilling equipment has rubber treads or tires and we use mats to reduce the impact of our equipment to the property. We always use screens to cover windows and walls during both the drilling and grouting phases of your project. This minimizes any mess that is created. We also have crew members clean as we go to clean up what little mess may happen. We protect your pool from grout intrusion with our specialty silt logs. We have created specialty systems such as our pipe truck and dump cart to insure the cleanest and most efficient project site. We continually evaluate your job during the entire grouting process.