Services

When it comes to foundation support, one solution does not fit all. Rather, for each particular project, Helical Drilling and its associated engineering experts select the right solution from among a broad range of available techniques. To examine the relationship between these techniques and their applications, view the Application Matrix.

The following is a list of the foundation support solutions used by Helical Drilling for existing structures or new construction: 
 
 

 

Conventional Helical Piles

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A helical pile is an assembly of mechanically connected steel shafts with a series pitched steel plates welded at specified locations on the lead section. Monitoring of the installation torque provides verification that the design capacity has been attained.

The piles are screwed into the ground (like a cork screw) using either machine mounted or hand-held hydraulic drill equipment. Helical pile working load capacities up to 25 tons can be installed with minimal headroom and within tight conditions.

Low mobilization costs, as well as no spoils allow conventional helical piles to be extremely competitive for pile loads less than 25 tons.

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Grouted Helical Piles

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The patented Pull-down Micro-pile, developed for soft clays in Western Canada, provides higher capacity helical piles. Recent load tests in Toronto verified 100 ton working loads. Our testing in New England has confirmed working loads of 35 tons.

Grouted helical piles can be installed with grout diameters of 4 to 8 inches. Steel shaft sizes are available in sizes ranging from 1.5 inches to 2.5 inches square. Unlike the conventional mini-pile process, there are no spoils with pull-down installations.

The load capacity of Pull-down Micro-piles is developed by either, end bearing on the helixes or friction between the soil and the grout, or a combination of both bearing and bond. The pile shaft can be installed with a casing to minimize down-drag forces.

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Compaction Grouting

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An increasingly popular and cost effective technique for ground improvement is compaction grouting. The soils within the improvement zone are densified by a systematic injection of controlled low mobility grout (slumps of 2 inches or less) under pumping pressures up to 900 psi.

The goal of the process is to achieve increased strength of the soil mass. An engineered grout program with the proper probe spacing, grout volumes and pumping pressures can achieve required design soil properties. The success of the grouting program can be verified by a post-grouting test program of borings or SPT tests.

The effectiveness of compaction grouting is directly related to several factors: the grout mix, injection rate, grout pump characteristics (hydraulics), grout hole spacing, soil mass response, and above all, the ability of the specialty contractor to understand and employ the technique properly.

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In soft organic soils where the ground cannot be improved by densification, compaction columns can be developed to transfer vertical loads from a foundation or a dense overburden layer through the soft soil to competent soil below. Compaction columns can also be used to increase the global stability of soils, supporting structures, with marginal shear strength or shear capacity.

Helical Drilling has used this technique to support heavily loaded warehouse slabs, rubble foundation walls, as well as conventional footings bearing over organic soils. Compaction columns have been used to reinforce poor soils supporting added surcharge loads due to expansion of roadways and railways. Slow pumping rates are used to minimize excess pore water pressure and shearing of weak soils. Spacing of compaction columns ranges from 4 to 12 feet.

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Rock fills are the primary application for limited mobility grouting. The objective is to deter further settlement by filling the voids in the rock fill. This is accomplished by choking off the stone fill just below competent overlying.

With the proper technologies and slump, a limited mobility grouting program is more cost effective when compared to conventional slurry grouting techniques. The need to pump excessive amounts of mobile grout is eliminated.

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Geopier®

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Geopier elements are constructed by drilling a cavity and ramming select crushed aggregate (stone) into the cavity in thin lifts. Geopier construction results in very dense aggregate piers used to support footings and reinforce soil and fill.

View/Download Geopier Brochure in Adobe PDF Format.

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Wetlands Walkways

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The conventional helical pile can be used in the support of light bridges, golf cart paths, and walkways through swamps and marshes. A series of braced bents consisting of helical piles are usually caped with a wood deck and railing system. The installation of a Helical walkway system limits the disturbance in environmentally sensitive areas.

Roadways and walkways can be installed in tidal areas or swamps using the "leapfrog" technique. Each additional supporting bent is installed by equipment supported on the previously constructed span.

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With the correct soil profile, helical tiebacks and soil nails can be more cost effective than conventional grouted tiebacks. Tiebacks and soil nails are installed to a prescribed torque that is correlated to the ultimate tension capacity.

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Curled slab repair

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Curled slabs-on-grade in warehouses, manufacturing facilities, and distributions centers often cause operational problems. The filling of the void between the soil and the bottom of a slab (usually less than ¼ inches) eliminates the usual bump of a forklift driving over the edge of a curled slab.

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