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Grouting 

 
Authors: Jack Caldwell

Summary

This review describes the use of grout in mining, including a review of the history of grouting, the use of grouting in mining situations to control subsidence, to provide for groundwater protection, to enhance the installation and functionality of roof and rock bolts and anchors, and to compliment shaft sinking operations. In this review we list and describe specialists in mine-related grouting, the design and specification of grouting programs, grout testing, grouting injection, and books and technical papers on the topic of grouting.

INTRODUCTION

This slim piece is the result of many hours scouring the byways of the web. I hope it saves you time and gives you a fast introduction to a technology that is key to many a successful mining operation. If you have more information, know of better sites, or can add to this, please pass it on and I will include your contributions in the next update.

HISTORY

In Middle English, before the French speaking Normans imposed their tongue on the Anglo-Saxons, grut was coarse meal, the grain used to make malt. I do not know how grut referring to grain transferred to grout as we use the word. I wonder if there is a link to the modern word grit (minute rough granules) from the Middle English gret = sand, from the Old English greot. Of course there is ground in modern English and grond in Dutch, with ground coming from the Old English grund. That gr-sound keeps us grounded. Maybe as the current theory goes, some influential, but probably mistaken, speaker used the word thus and thus it is.

I worked with Ken Weaver on a million dollar grout curtain for the embankment of the Cannon Mine tailings impoundment. Here is what he writes of the history of grouting:

The history of dam foundation grouting in the U.S., which began with a project in New York in the late nineteenth century, is-to some extent-one of objectives not fully achieved. It also is one of innovative procedures and insightful ideas only some of which were applied, and of questionable procedures that look all too familiar to today's grouting practitioners. An early suggestion that a closely adjacent two-row grout curtain consisting of closely-spaced grout holes might be preferable to a three-row curtain clearly was not incorporated in the design of Teton Dam, but has been incorporated in the design of a few dams constructed in recent years. The early twentieth century concept of injecting essentially endless volumes of high water/cement ratio grouts survived unto the late twentieth century, despite a realization in some quarters that such grout would travel far beyond the area requiring treatment and would either not set up at all or would merely form 'films.' By the time Boulder Dam was constructed, the design of grouting programs was considered to have became 'systematic.' However, in this case, remedial grouting entailing deepening the curtain and injecting very substantial volumes of grout subsequently was found to be necessary. There have since been many other cases in which the initial grouting was done 'systematically' (using now outmoded concepts and procedures) and in which remedial grouting ultimately proved to be required.

GROUTING TERMINOLOGY

Grout terminology is as specialized a language as any dialect or in-group-speak. Luckily for us the terminology is readily available at this link. My advice is to peruse it before undertaking any activity involving grouting. For the list is more than a dictionary—it is almost a primer on the technology and I learnt a lot just reading the individual items. For example here is one:

“Consolidation grouting: In rock, consolidation grouting consists of the injection of cement-based grout for the purpose of strengthening the rock mass by filling open structures and thus eliminating a source of settlement. Incidental to this main purpose, consolidation grouting may also serve to reduce the uplift potential beneath concrete dams by reducing the permeability. Generally done by drilling and grouting shallow holes on a grid pattern in the foundation area of concrete dams but may include “off-pattern” holes to treat selected geologic defects such as fracture of shear zones. The term is commonly and improperly used as a synonym for blanket grouting.”

This list of terms was published in civil engineering forums (to whom we are grateful for permission to link to it). I cannot help but wonder though if the terminology is different in the mining world. If you know, let me know.

My own experiences with grouting were many years ago in South Africa working for French company directing African workers. We used none of these terms, but communicated in an arcane Creole mix of French and Zulu and Afrikaans sprinkled with English swear words. Now I wish I had compiled a dictionary for that language, now probably passed into the mists of dead tongues.


TYPES OF GROUTING

Image courtesy of Hayward Baker The fastest way to become familiar with grouting in all its forms is to go to the Hayward Baker site where there is copious, quality information about compaction grouting, chemical grouting, cement grouting, jet grouting, and fracture grouting. No doubt you will want to stay on the site and become familiar with (and be impressed by) their expertise.


GROUTING TO CONTROL SUBSIDENCE

ESRI tells of grouting old coal mine workings to prevent subsidence and acid mine drainage - see also a beautiful paper by Paul Petzrick on the topic. Canada near Banff National Park has also done similar.


Image courtesy of Eco Grouting Specialists

SPECIALISTS

ECO Grouting Specialists has many case histories and a large number of fine publications on grouting in both civil and mining engineering.


GROUNDWATER PROTECTION

A grout curtain was installed to intercept shallow alluvial groundwater from the Success Mine tailings impoundment. Cadmium, lead, and zinc contaminated water was seeping to the South Fork of the Coeur d'Alene River.


GROUT TESTING

As bold as any commercial outfit, the University of British Columbia Geomechanics Group advertises their grout testing services, $150 for an unconfined compressive strength test of grout to be used for cable bolt installation or pressure grouting of rock formations.


GROUT CHARACTERISTICS

Here is a table from the EduMine course Practical Rock Engineering 5 - Excavation and Support, based on Evert Hoek's famous book of the same name.

Take the course and learn more about grout and many other things too.


BOLT & ANCHOR GROUTING

To keep rock anchors, bolts, etc in place we often grout them. Brochures on a plethora of grouting of anchors are available for download on the Dywidag-Systems site.


GROUTING CONFINED AREAS

Working with grout, even in confined spaces, is a lot easier with the ChemGrout CG-542.

The ChemGrout CG-542 Series are skid-mounted grout plants specially designed for work in confined work areas often found in mining. The CG-542 is low profile, compact, and ideal for the grouting of rock bolts and cable stays. They feature two 84 litre mix tanks; a 38 litre holding hopper and progressing cavity pump to provide a continuous, non-stop pumping process. A unique feature of these mix tanks enables the tops to be removed for quick and easy clean up.

 

Once mixed, material passes through the large slide gates of the tank outlet valves into the holding hopper. This is equipped with an auger to keep material thoroughly mixed while waiting to advance to the pump suction housing. A positive displacement, progressing cavity, rotor-stator type pump then delivers the material to the application. Operator controls are centrally located for efficient production. All components are easily accessible for operating, cleaning and maintenance.

Related Links

Grouting of Porous Aquifers During Shaft Sinking
Grouting and Shaft Sinking Through Water-Bearing Ground


BOOKS

Ken Weaver wrote a book called Dam Foundation Grouting. His book and many more on grouting plus additional information about grouting in the civil engineering context is the Geo Institute's Grouting Committee's developing site.

Soil grouting is the topic of a comprehensive new paper from BiTech Publishers and their premier magazine Geotechnical News. The paper is Soil Grouting – There’s Only One Way to View It. The premise of the paper is “permeation grouting is the way to get quality, control, and accountability.” This conclusion is based on the fact that “permeation grouting is the only kind of grouting for which design equations and relationships exist.” To back up this claim the paper includes long out-of-date and hard to access figures and tables that correlate standard soil properties with groutability. Moreover, the paper includes plenty of readable text and sound and solid information and guidance on planning a soil grouting program. I rather liked the one called the Rule of 3.5: “For permeation grouting, a maximum pumping rate near 3.5 gpm is reasonable and there will be a grout take of 3.5 gal/cu-ft of volume grouted.” Sorry, no metric measures given even though Geotechnical News is a Canadian publication.

The author of the paper is Dick Berry who edited the volume Grouts and Grouting: A Potpourri of Projects. This book and many more of grouting may be purchased at this link, namely the Geo Institute’s Grouting Committee Publications page.

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