Wright Underground Work

Serving the US and abroad with all your underground construction needs

Wright Underground Work

Mine Seals

The Jennchem J-Seal system is a simple, innovative, and cost effective permanent seal system for the mining industry.  Formwork is constructed of brattice cloth, brattice boards, and posts.  Supplied as a powder, the cement forms a low density foam (0.5 to 0.7 sg) when combined with the proper amount of air and water in the specially designed placer unit.  It yields with ground pressure to 60% of original height before brittle failure – a substantial improvement over conventional seals. Ground movement actually improves the seal. The minimum 400 psi product begins to gel in minutes forming a nontoxic, non-combustible product weighing approximately 1250 lbs/yd.  The lower causticity of the J-Seal mix allows safer handling than with other foamed cements.

Our seals are far above the competition in all performance aspects, in our opinion we provide the safest, strongest most cost effective seal that you could install in your mine.  We at Wright Concrete Underground, LLC have installed thousands of seals around the country for practically every major mining company.

Reinforced Concrete Seals

Over the years we have constructed new seals in front of existing old uncertified seals where there wasn’t enough distance to the outby rib corners to build a seal.  On one occasion we had two mats of HD Steel reinforcement drilled 3’ into roof and floor installed and tied throughout on 6” centers. Then a specially designed 6000 psi mix was pumped at high pressure down 980’ of borehole pipe from the surface to the mine below then out approximately 2500 LF to the seal locations to fill and pressurize the formwork to required specifications.

Spray Coatings

Spraying the ribs and fractured top in a seal line to reduce bleeding of oxygen and methane through the strata and around the seals inby and outby during seasonal and barometric changes is a regularly requested service we provide. Over the years we have developed great products and methods to best aid our customers in these areas.

TSL’s (Thin Skin Liners)

Although we spray many types of coatings for various underground applications our own designed TSL material Flex-Nite in our opinion (and many others) the flat out best thin skin liner (TSL) on the market today. This coating can be sprayed to various thicknesses and will help stop any scaling or spalling of rock by weather or other underground harsh conditions. It is also a superior flame retardant and is impermeable to water so no moisture will be allowed to get into the strata to start the deterioration process. All these factors along with the extremely low cost makes this a far superior product than any other on the market today.

Slope Construction

In June of 2004 we accepted the challenging task of placing approximately 1,200 cubic yards of concrete underground for PinnOak Resources, Oak Grove Mine in Bessemer, Alabama, just south of Birmingham. The job consisted of placing concrete on 4000’ of 18º slope 14 feet wide in the belt shaft that brings the coal out of the mine.

The project was basically two fold:  the company wanted a concrete bottom under the belt so they could wash any coal spillage to a pit at the bottom of the slope, and there had to be steps placed in the slope beside the belt for access to inspect, repair, and do the washing needed.

We decided the best possible method was to modify an already familiar product that we routinely use on the surface. We contacted our friends at ArmorForm and asked them if they could build us a form that has 8 inch thick steps 4 feet wide on one side and a 4 inch thick smooth section 10 feet wide on the other. Everything needed to be constructed into one manageably sized form.

After approaching Oak Grove’s CEO, Engineers, and Superintendents with our solution to their problem there was some skepticism as to whether this application would even work. But, armed with digital video of the test panel and the fact that no other companies solicited would even consider the project due to the incredibly long distance the concrete had to be pumped and the extreme condition the slope was in, Oak Grove awarded us the contract. They were highly impressed and pleased with the product once it was in place.

Over the years we have installed numerous slopes, all to the satisfaction of the customer. All have been under time constraints that we have met or exceeded.

Cellular Concrete

Cellular concrete is the combination of slurry (cement, fly ash, and water) and pre-formed foam blended together. Typically slurry is produced at a Ready-Mix plant and delivered to the construction site where foam is directly injected into the transit mixer or in line as it is pumped. The inline method is preferred because it allows for full load deliveries of Ready-Mix which is more cost effective.

Wright Concrete and Wright Concrete Underground have been using cellular concrete for several years now.  With density weights of 20 to 120 pounds per cubic foot and compressive strengths of 50 to 4000 psi, coupled with the ability to pump several thousand feet, cellular concrete gives our customers a wide range of uses.  Impoundment break-through protection, underground coal storage abandonment, archway void fills, longwall pass-through areas, decant pipe abandonment, and auger hole filling are just a few areas that we specialize in the use of cellular concrete. From an 80 yard decant abandonment to an 8000 yard impoundment break-through protection project, cellular concrete gives our customers an economic alternative to a wide range of project needs.

Void Fill

From filling voids over arches for roof support to filling entries after falls to creating false roofs for longwall shields to move through whatever the void regardless of size or strength needed Wright Concrete Underground, LLC cannot be beat on price or speed of project completion no matter what area of the country.

Cuttable Cribs

Cuttable Cribs are a two component system consisting of in most cases a 48” diameter cement pillar topped by a yielding bag. The cement pillar is a super strong breaker post designed to stop any falls caused by geologic anomalies in advance of the longwall face. The topper bag is designed to yield at 900 psi to the expected yield of the adjacent pillars, under abutment load. This designed yield preserves the structural integrity of the immediate roof by minimizing roof shear.


The cement required for the pillar is pumped down a borehole thousands of feet. The topper bag is filled with Tekset, a specially designed cement that facilitates yield under abutment load. The Tekset is mixed and pumped from an underground location, within 1,500 ft of the crib. Wright Concrete supplies all the necessary forms for the pillar, topper bags, underground pipe, borehole pipe, borehole drilling, surface mixing and pumping equipment. The underground equipment and material can generally be shipped to the job site on only a few flat cars.

Cuttable cribs have been extremely successful in both the Pittsburgh and Eagle coal beds, in entries as wide as 20 feet and as high as 11 feet. Cuttable cribs are generally placed in a single row on an average of 10 foot centers. For example, 4,000 feet of open entry would require 400 cuttable cribs. This includes closer spacing in and around cross-cuts. Cuttable cribs are located on wider 12-14 feet centers in entries parallel to the direction of panel extraction.

We have built cuttable cribs in Pennsylvania, West Virginia and Utah and have a couple versions to choose from depending on your particular condition. To save tremendous time on your longwall section when it comes to making that move call for our technical assistance.