Backfilling sands
Backfilling sands are used for making a hydraulically placed fill – a mixture of sand and water to fill voids created by an underground mining. Over the last few decades this has been the most popular form of the underground mining backfilling. Documented backfilling sands deposits occur mainly in the areas of the intensive underground mining, especially those of the hard coal and copper mining in the Upper Silesian Coal Basin and Lubin vicinities. One of the major requirements which sand deposits should meet to be classified as backfilling sand deposits is the location at the distance less than 50 km from the place where the raw material is to be used.
The majority of backfilling sand deposits is situated around the Upper Silesian Coal Basin. Three main deposit areas are differentiated: eastern, western and northern. The eastern area, which is the center of the production of that raw material, extends from Kuźnica Warężyńska through the Pustynia Błędowska Desert as far as the vicinities of Jaworzno. It is characterized by the occurrence of sands of fluvioglacial and locally eolian origin attaining up to 70 m in a maximum thickness (Pustynia Błędowska Desert). The second area with the largest resources comprises the Pleistocene valley of the Odra River in a part of the Racibórz Basin and a western part of the Silesian Upland and its sand deposits are from 15 m to 20 m thick at the average. The northern area comprises the Mała Panew River valley with its fluvioglacial sand deposits characterized by a significant thickness (up to 40 m). The deposits are explored well enough but have not been developed so far. Moreover, sandy-gravel deposits up to 30 m in thickness occur in the copper mining areas in the vicinities of Lubin.
The clastic rock raw materials occurrence in Poland (including backfilling sand) is presented on the map.
The table given below shows resources and the current state of exploration and development of backfilling sand deposits.
In 2017, anticipated economic resources of backfilling sands amounted to 2,517.61 million m3 (or about 4,279.94 million tonnes as recalculated using a weight-to-volume ratio 1.7 t/m3). Resources decreased by 123.90 million m3 mainly due to the crossing 2 deposits out from “The balance…”: Pustynia Błędowska – obszar pozostały (-79.72 million m3) and Szczakowa pole II (-84.14 million m3). The resources of listed deposits have been recognized as not available due to the current state of the area development and their occurrence partly below the groundwater level. These factors, together with the perspective of the lead and zinc mines in Olkusz region shutdown and with the cessation of the underground mining voids dewatering, result in backfilling sands deposits being useless for further exploitation. The significant resources drop was also recorded for Szczakowa-Bukowno deposit (-3.96 million tonnes) due to the reduction of the deposit area as the result of the land use changes. Remaining, minor resources drops – at the amount over a dozen thousand m3 – were the result of the exploitation and losses in the developed deposits. The anticipated resources growth was recorded for Szczakowa pole I deposit (+50.67 million m3) due to the elaboration of a new documentation with recalculated resources. The part of the resources documented so far as anticipated sub-economic was recognized as anticipated economic.
Economic resources decreased by 3.22 million m3 in comparison with 2016, due to the exploitation and losses. In 2017 no new deposit development plans for backfilling sands deposits have been elaborated.
The production of backfilling sands totaled 2,697 thousand m3 (4,585 thousand tonnes) being by 214 thousand m3 (7%) lower than in the previous year. The production dropped in 4 out of 8 exploited deposits with the most significant decrease for Pustynia Błędowska – blok IV deposit (-131 thousand m3). The exploitation from Kuźnica Warężyńska deposit is still on hold.
The figure given below shows changes in domestic resources and production of backfilling sands in Poland in the years 1989-2017.
Prepared by: Agnieszka Malon
Table 1. Backfilling sand - million m3