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Site Report

TS 1330

Mine Workings Stabilised with Pumped Concrete

In the course of work to close down the Leonie iron-oremine in the Ober Pfalz in West Germany, it is necessaryto fill galleries close to the mine shaft in order to preventsubsidence which might otherwise result from therelatively shallow depths involved.

The long-stroke BSA 2100 HE pumps air-entrained foamconcrete underground as filling material during all weather conditions

The underground management has decided to have thesump gallery system filled at a depth of some 190metres. The work is made considerably more difficult by

inrushes of water. The filter material is an inexpensivefoam concrete (grain size 0–4 mm) with a high proportionof entrained air (20% by volume). This choice of materialtakes into account the poor strength properties of thesurrounding geological structure (marl, clay). A high fillingrate results in economical operation. A further positiveaspect is that the foam concrete retains its volume aftersetting – which would not be case with normal concrete.The material is expected to achieve its final strength after50 days.

The sump gallery system to be filled con-sists of anorthern and southern section. lt has a total of some5,100 m

3, which is being filled in two stages. At the time

of our visit, work was in full swing on the filling of thesouthern section. 10-hour shift operation allows a dailyinput of 400 m

3 of material to be achieved. A long-stroke

Putzmeister BSA 2100 HE concrete pump feeds thefoam concrete from the surface directly to the placingpoints underground. The machine has been installedunder cover in the shaft hall, enabling operation tocontinue without interruption under all weatherconditions. Truck-mounted concrete mixers bring the

material from the concrete works 5 km away and unloadthe foam concrete into the hopper of the concrete pumpfrom a ramp. The BSA 2100 E first feeds the fillermaterial 15 m horizontally to the shaft through a 125 mmdiameter Putzmeister ZX high-pressure pipeline.

80 m long Putzmeis ter ZX delivery line laid horizontally . Thanks to gentle pumpingcharacteristic of the BSA 2100, only wood needs to be laid below the line

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 A vent bore hole in the 90° pipe bend improves flow behavior

The 90° pipe elbow at the shaft entrance incorporates ableed connector which is used to bleed the material of airas required. This »trick« not only improves the flowcharacteristics of the foam concrete but also reduces thedelivery pressure which the BSA pump needs to produce.The delivery line then runs for some 185 m verticallydown the shaft and then for a further80 m horizontally along the main road. A gate valve,

capable of operating at up to 130 bar, has been fitted inthe pipeline in the main gallery. At the end of the road,the PM pineline is connected to the mine’s own pipeswhich continue down to the lower-lying sump gallerysystem.

Thanks to the damped pumping characteristics of theBSA 2100, it has proved possible to lay the delivery linewithout anchoring. In the roadways, the pipeline is merelylaid on wooden supports, while running vertically in theshaft it is supported only by brackets on the shaft wall atintervals of 6 m.

In the actual sump system itself, suspension chainssecure the delivery pipeline to the mine workings. Assoon as a section has been filled in the sump system(retaining dams prevent the foam concrete from flowingback into the gallery), a quick-action gate valve shuts offthe lost line. The piping system is then transferred to thenext section to be filled. The quick-action gate valve canbe recovered 24 hours later.

 At the discharge point, a pipe elbow pointing towards theroof ensures complete filling until the material meets theroof.

The pipe delivery system described,including a robust high-performance Putzmeisterconcrete pump, allows work to be carried out rapidly inonly a few days.

Minimal preparation costs, high reliabi-lity in operationand ideal adaptability to the special requirements ofunder-ground working are the distinguishing features ofthis economic method for concrete handling in the Leoniemine.

Discharge of the foam concrete in one section of the sump gallery system