Grouting is able to prevent leakage in underground works (e.g. tunnels and foundations) in soft water rich sediments. However, one problem with grouting is that there is no good way to control the shape and location of the grout body, and injection of the grout often turns out to be a random operation. Therefore, in many occasions leakage occurs because the grout body is not in the right location. Other failures are linked to the fact that the grout body is too thin or not strong enough, or the grout body is discontinuous. Groundcontrol and her associates are able to solve these problems with their injection techniques, stronger grout mixtures, and tiltmeter monitoring and mapping system, combined with computer techniques to provide an early warning system for leakage.

Groundcontrol and her North American associates have unique ground monitoring and reinforcement technology which can drastically reduce the cost of geotechnical ground stability problems compared to conventional methods. By combining fracturing technology with proprietary, quick setting, and environmentally friendly micro-fine cement grouts, unstable ground can be reinforced in situ without the need for costly and disruptive excavation and/or conventional reinforcement techniques.

This process, known as Fracture-Permeation Grouting, is a relatively new method of strengthening weak or unstable soils and bedrock by the injection of cement grout into the target formation. The method originated in Europe (Byle and Borden, 1995) and consists of creating controlled subsurface ground fractures that are injected with a thick grout. The method densifies the ground, decreases local permeability, and creates hardened grout lenses that stiffen and strengthen soil and/or bedrock. Fracture-permeation grouting has traditionally had limited applications in the geotechnical industry because of inadequate means of measuring the extent and geometry of grout lenses, inappropriate injection equipment, and inferior grouts (usually Portland cement or chemical grouts). Groundcontrol and her associates have overcome these limitations through the use of proven, proprietary fracturing equipment and proprietary ultra-fine, high strength cement grouts, and remote monitoring of grout fracture geometry using surface-mounted tiltmeters.

Many problems with grouting are the result of uncertainty in the geometry and continuity of the grout body. Groundcontrol and her associates have solved this problem. The placement, location, and geometry (continuity) of subsurface grout lenses injected into unstable or weak ground can be accurately mapped using surface-mounted tiltmeters during the fracture-permeation process. Tiltmeters are highly sensitive instruments (nanoradian and microradian resolution) used in the oil and gas industry to measure the minute ground surface deformations created during the fracturing of petroleum reservoirs to stimulate production. The direction and magnitude of ground surface deformation or "tilt" measured by tiltmeters is used to determine the shape, thickness, extent and orientation of fractures in the subsurface. This tiltmeter technology has been adapted for use in mapping subsurface properties in shallow (typically less than 500 metres depth) soil and bedrock.

Our use of specialized fracture and pressure-transient mapping services span a range of applications including grout barrier emplacement, construction dewatering, fracture-permeation grouting, soil fracturing, pipe bursting, and leakage problems, among others. Through the combined use of these innovative technologies, we offer clients a superior and less expensive alternative to many conventional geo-environmental applications.

After the grout body is mapped using our tiltsensor array we are able to tell if leakage may occur if water is still flowing due to the ambient hydraulic gradient. Because we are able to tell the client whether there may be discontinuities in the grout lens, the client can rapidly decide to repeat or improve the grouting operation.

The tiltsensor array can stay in operation to serve as an early warning system. Prior to leakage occurring, accumulation of fluid occurs against a grout barrier, which is detectable with the tiltmeter system. Therefore, this early warning system gives the client an opportunity to react before structural damage occurs.

The techniques of Groundcontrol and her associates are particularly applicable for subsidence monitoring and abatement, grouting, tunnelling and combinations of these processes. These methods are cost effective and give astonishing good results in comparison with conventional techniques.

References: multiple jobs have been done in the US, Canada and the Netherlands – references available upon request