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Spectra Geotechnologies Foundations Contracting L.L.C
Spectra Geotechnologies Foundations Contracting L.L.C

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Grouting Ground Treatments

Spectra Geotechnologies Foundations Contracting L.L.CBy virtue of proximity of marine conditions (in plan and elevation) and the excessive hydraulic conductivity of the native soil and rock stratigraphy  (sand and weak, highly fractured rock ground masses), ingress of water and build-up of pore pressures beneath and around construction, and the inherent low density and strength of ground masses, construction on and underground is laden with issues related to excessive water ingress, and weakness that often beg the need to deploy groundwater exclusion and strengthening methods.
 
These measures counteract these tendencies. Soil and rock injection with carefully selected grout materials is one of the many available practical applications available address these difficulties.

Injection Mechanism :

  1. Permeation Grouting in which the injection material is thrusted through drilled grout holes, under pressure to impregnate with selected grout materials the primary and/or secondary pore space of the ground; thereby densifying, strengthening and rendering less permeable the ground mass to be injected. Permeation grouting is normally applied through grout tubes and grout holes are sealed off and pressurized using a combination of manchettes and packers.

  2. Frac Grouting; Also known as "claquit" or hydro-fracture grouting, in which the grouting pressure in the grout holes are raised to beyond the hydro-fracturing pressure of the ground mass injected; associated with the creations and propagation of newly induced fractures that would be impregnated by the strengthening and possibly densifying grout and with the result that the mass injected is thus improved. Frac grouting is applied through grout holes installed with grout tubes and sealed off and pressurized using manchettes and packers.

  3. Fill Grouting; in which large sub-terrain voids are penetrated by injection holes and vent holes and the grout is placed at the bottom of the void and allowed to fill the void under gravity or low pressure flow regime in an upward displacement process until the grout emerges from the vent holes. Free-flowing micro-concrete often is used as the injection material for practical and economic considerations. Fill grouting is carried out normally through gravity or pressure tremies.

  4. Compaction Grouting; is applied to weak soil to achieve lateral compaction along with creation of a strong grout mass column which when applied on a grid results in an increase in the overall strength & stiffness and reduction in soil compressibility. Normally either a stiff mortar-like cement grout is applied to the drilled grout hole or else free-flow grout is applied inside a strong, expandable geo-membrane tube that expands inside the soil laterally.

Grouting Materials :

Injection materials range in material composition combinations to a wide range of components with the purpose of achieving the intended results with the least time, effort and cost. These material are:

  1. Cementitious Materials: Such as Portland cement (all types; including ultra fine cement), slag cement (GGBS), fly ash, silica fumes etc with different combinations and additives.

  2. Muds; including all types of bentonite slurries; in combination with cements or alone with water and additives. Proper hydration of bentonite to mobilize its colloidal behavior is key in its preparation for injection.

  3. In-organic (normally Silicate)-Based Chemical Grouts; in combination with cements or other chemical systems like reactors, accelerators, catalyst etc. these materials  can be controlled in consistency and setting time to achieve what slurry grouts fail to do and are applied at controlled pressures and quantities. They are introduced through tubes installed on grout holes that have been sealed off by using manchettes and packers. Cost of chemical grouts are higher than their cementitious or mud slurry counterparts.

  4. Organic-Based Chemical Grouts : These are based on a range of organic co-polymer materials like acrylics, epoxies, elastomeric chemicals (foaming and non foaming). They are characterized with low viscosity and thus high penetrability, and are quick setting (or quick foaming) in nature. Their main disadvantage is their high cost compared to all other counterparts mentioned above and thus the case for their application must be carefully considered and justified.

Applications :

Grout Injection in particular is one of SGFC's main portfolio activities and has been applied to serve a variety of purposes in several sectors such as;

  1. Subsoil densification and strengthening of rock masses to improve bearing capacity and counteract compressibility and settlement for buildings, infrastructure and facility foundations.
  2. Sub-terrain void and cavity filling of ground masses ( natural and filled areas) underlying areas proposed for development.
  3. Construction of curtain walls and other local seepage cutoffs purposed to combat excessive water ingress  into excavations, underground works and basements and to facilitate effective dewatering on difficult sites.
  4. Strengthen and render less permeable rock masses around underground excavation and tunneling.
  5. Intercept influx of gas under high pressure, originating at depth and extruding into deep excavations and drillings.
  6. Fixing and strengthening of tie-backs (anchors, soil nails and rock bolts).
  7. Abandonment works for wells, pipelines, abandoned underground structures and drillings.
  8. Alternative shoring systems combining grouted curtain walls, tie-backs and shotcrete, in combination with modest intensity of dewatering.
  9. Construction of grout columns such as compaction grout columns, frac grout columns, permeation grout columns and jet grout columns for the support of building, facility, infrastructure and earthworks foundations.
  10. Construction of mini-piles and micro-piles with or without ground improvement.
  11. Repair of underground structures, improvement of bearing capacity of foundations including pile capacity.
  12. Under-pinning of building, infrastructure and facility foundations adjacent to excavations.
  13. re- leveling of foundations and pavements.
  14. Other project-specific applications; such as construction of catholic protection and earthing wells for oil & gas and other industrial applications.