Design of the shaft lining for deep salt deposits
of significant thickness
Sławomir FABICH
1), Joanna ŚWITOŃ
1), Sławomir ŚWITOŃ
1)1) KGHM CUPRUM Sp. z o.o. Centrum Badawczo-Rozwojowe, Wrocław,
e-mail: sfabich@cuprum.wroc.pl
Abstract
The Polish Copper Belt is situated in the Fore-Sudetic Monocline in the Lower Silesia. The characteristic feature of the northern part of the copper ore deposits is the presence of the rock salt layer in the Zechstein Kupferschiefer formation, located more than 1000 m below the surface. Thickness and depth of the salt deposit layer increase with the ore body’s dip direction. Due to this the thickness of the salt deposit exceeds 100 m at the new shafts locations. The shaft lining design must take into consideration the geomechanical properties of the rock mass. The main issue with lining selection in rock salt is to prevent time dependent (creep) radial deformations, causing the shaft excavation to close up over time. Under these conditions, shaft lining designers are faced with the challenge to create innovative solutions that will be able to protect the shaft excavation permanently, effectively and safely. The paper presents the authors’ own experiences with the existing shaft linings in the presence of salt layers, as well as a new design solution for permanent shaft protection in a way that does not require its cyclical reconstruction.
Key words: shaft lining, deep salt deposits, rock salt creeping
Projekt obudowy szybowej w warunkach zalegania głębokich
pokładów solnych o znacznych miąższościach
Streszczenie
Legnicko-Głogowski Okręg Miedziowy znajduje się na monoklinie przedsudeckiej na Dolnym Śląsku. Charakterystyczną cechą górotworu stanowiącego otoczenie północnej części złoża rudy miedzi jest występowanie w utworach cechsztyńskich na głębokości ponad 1000 m warstwy soli kamiennej. Jej miąższość oraz głębokość zalegania wzrasta zgodnie z kierunkiem zapadania złoża. Z tego powodu, w miejscach lokalizacji nowo projektowanych szybów, miąższość pokładu solnego znacznie przekracza 100 m. Projekt konstrukcji obudów szybowych musi uwzględniać właściwości geomechaniczne górotworu. Głównym problemem związanym z wyborem obudowy w soli kamiennej jest zapobieganie skutkom radialnych deformacji wynikających ze zjawiska pełzania, które powodują, że wyłom szybowy z czasem ulega stopniowemu zaciskaniu. W tych warunkach projektanci obudów szybowych stają przed wyzwaniem stworzenia innowacyjnych rozwiązań, które będą w stanie trwale, skutecznie i bezpiecznie chronić wyrobisko szybowe. W artykule zostały przedstawione własne doświadczenia autorów związane z obecnie funkcjonującymi obudowami szybów na odcinkach solnych, jak również nowe rozwiązanie projektowe obudowy, które, w opinii autorów, trwale zabezpieczy wyrobisko szybowe w sposób niewymagający jego cyklicznej przebudowy.
Introduction
KGHM Polska Miedź S.A. engages in the extraction of copper from ore deposits located in the south-western part of Poland. KGHM operates in the Legnica-Głogów Copper Belt (LGOM) placed on the southern edge of the Fore-Sudetic Monocline. Three basic stratigraphic units have been distinguished here: the metamorphosed Proterozoic-Paleozoic substrate, Permo-Triassic formations, which gradually dip in the north-east direction, and the subhorizontal thick layer of the Cenozoic sediments. In the southern part of the Fore-Sudetic Monocline two hydrogeological complexes have been identified:
Cenozoic complex, including loose Quaternary and Paleogene-Neogene formations, 300-400 m thick;
Permo-Triassic complex, occurring in solid rocks of Bunter, Zechstein and Rotliegend, with the thickness increasing in the NE direction and exceeding 1,000 m in the northern part of the area.
The copper ore deposits dip monoclinally at the depth from several hundred to 1,500 m. They are stratoidal and occur in sedimentary rocks of Zechstein with the diversified thickness reaching up to several meters. In the ore series fault zones are present with displacements up to several dozen meters.
KGHM Polska Miedź S.A. has currently the concessions for copper ore extraction from 7 deposits: "Lubin-Małomice", "Polkowice", "Rudna", "Radwanice Wschodnie", "Sieroszowice", "Gaworzyce" and "Głogów Głęboki-Przemysłowy" (GG-P) (fig. 1). The LGOM copper ore deposits have been developed by 30 shafts so far with the depth from 500 to 1,250 m and the 6 or 7.5 m diameter. Three shafts were decommissioned and only 27 operate at the present time.
The 31st shaft is currently under construction. It is located in the central part of the "Głogów Głęboki-Przemysłowy" mining area with the target depth of 1340 meters and the diameter of 7.5 meters. The GG-1 shaft sinking is expected to be completed by the end of 2020. It will be the deepest of all shafts explored up to now in the Copper Basin.
The characteristic features of the rock mass surrounding the northern part of the copper ore deposit are the deepest location of copper-bearing rocks from all presently extracted deposits in LGOM and the rock salt layer of considerable thickness at the depth exceeding 1000 m, occurring in Zechstein formations. Its thickness and depth increase in the dip direction of the copper ore deposit. For this reason, the thickness of the rock salt layer exceeds 100 m significantly in places where new shafts could be designed.
Fig. 1. Mining areas and mine shafts in LGOM
1. Genesis and properties of rock salt lying above the copper ore
deposits within the Fore-Sudetic Monocline
Less than 270 million years ago, the climate in Poland was hot and dry. The shallow Zechstein Sea flowed in from the north-west and stopped on the mountain ranges: the Sudetes and the Świętokrzyskie Mountains. Cyclical fluctuations in see level caused the development of characteristic rock sequences. Seasonal loss of connection between the Zechstein Sea and the global ocean made the sea turn into the highly steaming lake. This led to the precipitation of large rock salt deposits, as well as calcium and magnesium carbonates (calcite, dolomite) and calcium sulphates - anhydrite and gypsum.
The Zechstein Sea was associated with copper and silver deposition. Those metals have been accumulated as a result of the metalliferous solution flow through the contact rocks between Rotliegend and Zechstein (sandstones, shales and dolomites), which caused their oxidation and zonal distribution.
Within the LGOM area, above the copper ore deposit, the rock salt layer was being formed during the Permian period. It builds one of the lithological units of the Zechstein cyclothem called Werra (P21). The deposit is considered as the irregular WNW-ESE trending layer, smoothly dipping to the NE at an angle of 3° ÷ 8° (locally up to 15°). Its thickness ranges from 0 m from the S and SE side, to 186 m to the N and NW side (fig. 2).
Fig. 2. Geological cross-section illustrating the location and thickness of the rock salt deposit in LGOM: 1. Rotliegend; 2. Zechstein formation; 3. the Oldest Rock Salt (Na1); 4. Triassic;
5. Paleogene and Neogene, 6. Quaternary, 7. Tectonic dislocations
The Oldest Rock Salt has been developed in the form of a diversified complex of layers, in which the main component is halite. The base part of the complex is laminated with bright pure salt laminas of the thickness varying from 3 to 30 cm, and darker or black anhydrite laminas of the thickness varying from 1 to 10 cm. Most often salts in this part of rock complex have a multi-grained medium- and coarsely-crystalline structure, in some parts porphyritic. The laminated salts are covered by pure and slightly contaminated salt layers, which are the major part of the salt complex. They have multi-grained medium- and coarsely-crystalline structure, massive texture and milky or transparent color. The crystal size usually ranges from 0.5 to 0.7 cm. The main contaminations of these salts are anhydrites in the form of breccia, as well as regularly or irregularly distributed loam dopants.
Rock salt is a medium strength and low elasticity rock, having rheological properties. The impact of time on salt behavior under load becomes evident in the creep phenomenon (with constant load the strains increase) or in the strain relaxation phenomenon (with constant strains the stresses decrease). In addition, a contribution of elastic deformation to the total salt deformation is small. When the yield strength is exceeded, there is a process of strains continuous increment in the rock salt, i.e. the transition from the creep stage to the flow stage of the material. The creeping process of a salt rock mass is influenced by such factors as the stress concentration as well as temperature and humidity.
The rheological properties of the salt massif are usually manifested in the convergence of underground excavations located within it. In order to predict the scale of deformation, one should estimate the parameters of the constitutive equation of the rheological model describing the behavior of the specific salt type. It can be done on the basis of long-term tests or measurements such as:
laboratory creep tests with constant load,
in situ convergence measurements in excavations located in the salt rock mass.
2. Influence of the salt rock mass behavior on the process of shaft
lining design
The rock salt layer of considerable thickness is present in the profile of 7 shafts located in the mining areas: "Sieroszowice" (shafts SG-1, SG-2, SW-1 and SW-4), "Rudna" (shafts R- IX and R-XI) and "Głogów Głęboki-Przemysłowy" (shaft under construction - GG-1) (tab. 1).
In the LGOM shafts, in the section passing through the rock salt, various lining designs have been implemented so far (tab. 1). The shaft lining constructions are dependent on the deposit depth and the thickness of the rock salt layer.
Table 1. The depth of rock salt layer with the type of lining used in the LGOM shafts on the salt interval
Mining area Shaft
Rock salt interval
Rock salt
thickness Shaft lining
m m
Sieroszowice
SG-1 933.5 – 951.5 18.0 masonry-concrete and concrete lining with air gap
SG-2 957.5 – 987.1 29.6 tubing lining with concrete backfilling SW-1 863.4 – 875.2 11.8 tubing lining with concrete backfilling SW-4 1026.3 – 1181.8 155.5 bolts-shell lining reinforced with
steel profiles V25 Rudna
R-IX 965.6 – 986.6 21.0 tubing lining with concrete backfilling R-XI 1125.4 – 1137.0 11.6 concrete lining with styrofoam
backfilling Głogów Głęboki-Przemysłowy GG-1 1145.7 – 1215.2 69.5 (under construction) 5 layer lining:
2 tubing lining layers with concrete backfilling and yielding foam backfilling
In the R-XI shaft the concrete of C25/30 strength class and W10 waterproof resistance have been used. In addition, there are the styrofoam blocks behind the concrete wall, which were put into a ring and connected through solvent-free glue. The empty space between the rock mass and the styrofoam ring has been filled with styrofoam plates. Styrofoam blocks were assembling from bottom to top together with applying a concrete mix with the use of a 1.0 m high rearranged formwork. In order to protect the concrete lining against the possible tensile forces, reinforcement have been used in the form of a mesh with dimensions of 2.4 x 1.5 m and 2.1 x 1.5 m, distributed uniformly around the shaft perimeter [2].
In the shaft SW-4, where the depth of the salt layer and its thickness are the largest from whole existing shafts in LGOM, the bolt-shell lining reinforced with V25 steel profiles has been used [1]. Three-element system, including a spraying system consisting of a polyurethane undercoat with a thickness of ~ 2 mm, a tensile mining mesh and a membrane with a thickness of ~ 5 mm, has been applied as a preservative shell protecting the salt wall against the atmosphere in the operating shaft. The tensile mining mesh with a load capacity of 50 kN/m has been used to reinforce the system against the salt overhangs arising as a result of plastic deformation of the massif. It was stabilized to the shaft wall with Hilti nails. The membrane was pressed to the shaft wall with yielding steel arches (every 0.75 m)
and fixed with cuttable resin bolts in which, from the depth of 1099.2 m, the length of the rod was reduced up to 0.5 m due to unfavorable working conditions in the salt massif. The part of the bolt rods projected more than 200 mm beyond the shaft wall has been equipped with two washers separated by a rubber hose and a nut. The nuts were screwed on the entire thread height eliminating damage to the washers. The yielding steel arch lining has been applied as the additional support in order to take up deformations resulting from the creeping process of the salt massif. It was constructed of the V25 steel profiles with a spacing of 0.75 m. The individual arches were connected each other by RSM tubular struts of 750 mm length and fixed to the salt wall with two screw anchors of 1.8 m length. All steel elements of the yielding lining were protected against corrosion by hot-dip galvanizing with a protective layer thickness of 70 μm. In addition, the arches were made of steel of more than three times higher corrosion resistance to saline water compared to standard steel types. The technology of shaft sinking and lining application in the salt interval depends on the lining construction. Generally, the salt walls were extracted by blasting, except the SW-4 shaft. The KDS-2 shaft-sinking roadheader was used there due to the large thickness of the salt layer (over 150 m) and the necessity of obtaining a regular circular cross-section of the shaft walls because of the specific lining construction. This type of roadheader was previously applied to excavate the frozen Cenozoic layers (mules, sands, gravels, brown coals, silts) in the depth up to about 400 m. It was first time in LGOM when the roadheader was used to sink the shaft below 1000 m of its depth.
The lining design process in the SW-4 shaft on the salt section was one of the most difficult that had been occurred in shaft construction history in LGOM. It resulted from the natural, rheological properties of rock salt and the considerable depth of the salt deposit with a very large thickness. The designed shell lining reinforced with steel arches was not fulfilled its function. After a few years it was necessary to reconstruct it due to the increased convergence of the shaft walls alongside the salt interval (measurement sites were located on different depths below ground level (b.g.l.) (fig. 3). However, the SW-4 shaft convergence is still in progress although at a lower rate than before the first lining reconstruction (fig. 4). Probably in the next years another shaft lining reconstructions alongside the salt interval will be necessary to conduct.
Based on the experience associated with the operating shafts with the salt walls, especially in the SW-4 shaft with the largest thickness of the rock salt layer in LGOM, it has been considered to design an innovative lining construction that would guarantee safe conditions throughout the lifetime of the shaft.
Since the specific function of the GG-1 shaft (hoisting and ventilation) absolutely excludes any operation stops intended to possible rebuilding, it was necessary to design lining that would be able to fully carry the expected pressure resulting from the salt massif creeping. The lining construction should also provide the safe operation of the shaft until the "Głogów Głęboki-Przemysłowy" deposit will be completely depleted. The anhydrite interlayers, particularly visible in the region of salt-anhydrite breccia in the GG-1 shaft profile, may result in some difficulties in maintaining the stability of the shaft walls. Anhydrite rocks splitting as a result of the salt creeping determines the use of the additional local-placed support.
The presence of the salt layer in the shaft profile therefore determines the design process of its lining. It is very important to assess the behavior of the salt massif, especially immediately after shaft sinking. At the same time, the shaft lining
construction should be based on the solution that fully transfers the rock mass pressure. Due to the fact that the salt creep process is started immediately after the shaft walls unveiling, it is very important to determine the proper diameter of the shaft, so that at the time of applying the final lining it has at least a nominal value. The further part of the article presents the details related to the design and construction of the shaft lining on the salt section in the GG-1 shaft, which, according to the authors, would guarantee safety throughout its whole lifecycle.
0,00 100,00 200,00 300,00 400,00 500,00 600,00 700,00 800,00 900,00 0 100 200 300 400 500 600 C on ve rge n ce ( avg) [ m m ]
Days (Timepoint 0 - 1st Feb 2013)
Site 1 - 1061.0 m b.g.l. Site 2 - 1084.5 m b.g.l. Site 3 - 1099.5 m b.g.l. Site 4 - 1114.5 m b.g.l. Site 5 - 1129.5 m b.g.l. Site 6 - 1144.5 m b.g.l. Site 7 - 1159.5 m b.g.l. Site 8 - 1174.5 m b.g.l.
Fig. 3. Convergence of the SW-4 shaft alongside the salt interval (before the first shaft lining reconstruction) 0,00 100,00 200,00 300,00 400,00 500,00 600,00 700,00 0 100 200 300 400 500 600 700 800 900 1000 C on ve rge n ce ( avg) [ m m ]
Days (Timepoint 0 - 25th June 2015)
Site 1 - 1061.0 m b.g.l. Site 2 - 1084.5 m b.g.l. Site 3 - 1099.5 m b.g.l. Site 4 - 1114.5 m b.g.l. Site 5 - 1129.5 m b.g.l. Site 6 - 1144.5 m b.g.l. Site 7 - 1159.5 m b.g.l. Site 8 - 1174.5 m b.g.l.
Fig. 4. Convergence of the SW-4 shaft alongside the salt interval (after the first shaft lining reconstruction)
3. Method for evaluation of the shaft breach diameter in the salt massif
The general model of salt massif behavior in the LGOM area has been determined based on the real convergence measurements. They were conducting from February 1, 2013 to June 11, 2014 at 8 levels of the salt section in the SW -4 shaft profile before reconstruction of the SW-4 shaft lining in the salt interval. In the purpose of predicting creep rate of the rock salt deposited in the overburden of copper ore deposits on the Fore-Sudetic Monocline, the classic linear viscoelastic Burgers model was fitted to measurements data from SW-4 shaft using statistical analysis software Statistica v.10. This four element statistical model is a combination of two others: the Maxwell model and the Kelvin-Voigt model (connected in series) [4], in the following form:
(1)
where:
u(t) - one-sided horizontal convergence of the side wall in time t, m σp - primary vertical stresses in salt rock mass, MPa,
a - radius of shaft breach, m,
t - time from the salt side wall unveiling on the specific depth of the shaft, day,
GK - shear modulus of Kelvin body, MPa, GM - shear modulus of Maxwell body, MPa,
ηK - viscosity coefficient of Kelvin body, MPa∙day. ηM - viscosity coefficient of Maxwell body, MPa∙day.
The indicators of the creep rate of rock salt are the Kelvin and Maxwell body shear moduli as well as the viscosity coefficients of those two elements. Their estimation was performed using the Lavenberg-Marquardt's non-linear least-squares method, which is an extension of the Gauss-Newton algorithm [5]. Consequently, the 8 sets of creep model parameters were evaluated for different depths on the salt section in the SW-4 shaft, assuming that the initial radius of the shaft breach was 5 m, and its convergence was uniform over the entire circumference.
The obtained statistical models, allowing to determine the creep rate of the salt medium at various depths in the SW-4 shaft, were calibrated in the FLAC 2D software by numerical simulation of the shaft breach convergence increasing in time. The axisymmetric model of the stratified rock mass consisted of gray and dark gray anhydrite, anhydrite and clay breccia, rock salt and gray and gray-beige anhydrite (fig. 5) was implemented for analysis in accordance with the actual system of rock layers in the vicinity of the SW-4 shaft. The zero displacement boundary conditions were defined at the lower edge of the model. The upper edge of the model was loaded with vertical pressure reflecting the influence of overburden rocks. Variable horizontal pressure changing with the depth and conditions of the rock mass was applied to the lateral edge. It was assumed that all layers except rock salt were considered as the elastic-plastic materials. The salt rock layer was divided into 8 intervals, to which the appropriate parameters of the Burgers model were assigned, estimated using the Lavenberg-Marquardt method, adjusted to the data from subsequent measurement stations in the SW-4 shaft.
Fig. 5. Axisymmetric finite-difference model of the rock mass surrounding the SW-4 shaft
Calibration of statistical models describing the behavior of the salt massif was carried out by comparing the values of horizontal displacements measured at individual measurement stations in the SW-4 shaft to the values of horizontal displacements calculated with FLAC 2D in the points of the numerical model corresponding to the location of measurement stations. The values of the calculated horizontal displacements were read for the time points corresponding to the dates of measurements carried out in the SW-4 shaft. Timepoint 0 means the moment of salt wall unveiling at the level of the measurement station in the shaft, i.e. the moment at which the creep process began. Figure 6 presents the example of comparison of real and calculated one-sided horizontal displacements of the shaft breach obtained at measurement site No.1.
Fig. 6. Comparison of measured and calculated in the FLAC 2D shaft wall displacements in the SW-4 shaft
Eventually, only a slight modification of the viscosity coefficients and shear moduli values estimated using the Lavenberg-Marquardt method have allowed to obtain a good agreement between shaft wall displacements calculated in the FLAC 2D with measured at all 8 measurement stations in the SW-4 shaft (tab. 2, fig. 7).
Table 2. Parameters of the Burgers model after calibration separately for 8 measurement stations on the salt wall in the SW-4 shaft
Benchmark N° Benchmark depth Shear modulus of Kelvin’s body Viscosity coefficient of Kelvin’s body Shear modulus of Maxwell’s body Viscosity coefficient of Maxwell’s body H [m] GK [MPa] ηK [MPa*doba] GM [MPa] ηM [MPa*doba] 1 1060,70 353 21 991 1 693 144 935 2 1084,60 353 5 651 1 690 125 706 3 1099,60 353 5 208 1 690 104 167 4 1114,60 353 12 037 1 282 121 528 5 1129,60 353 5 709 4 805 115 741 6 1144,60 353 4 977 1 690 138 889 7 1159,60 353 9 259 1 690 150 463 8 1174,60 380 5 709 1 690 344 907
In order to predict the creep rate and the side wall displacements magnitude in the GG-1 shaft to identify the appropriate diameter of the shaft breach, ensuring safe work conditions, it was assumed that the rheological properties of the salt massif in the GG-1 shaft profile are the same as determined at corresponding depth intervals in the SW-4 shaft profile. This simplification can be justified by the short distance between two shafts of around 5 km.
The predicted creep rate of salt walls in the GG-1 shaft at a distance of about 30 m from the roof and bottom of the salt layer after approximately 80 days from the unveiling of the side walls (after stabilizing the creep process) reached value of about 0.6 mm/day (determined for the designed shaft breach diameter of 11.54 m).
Fig. 7. Distribution of the Kelvin (ηK) and Maxwell (ηM) body viscosity coefficients depending on the depth in the GG-1 shaft profile
Based on the calculated results, it is anticipated that at a depth of 1,788.6 m in the GG-1 shaft, from the moment of unveiling the side wall to the moment of installing the final lining, the maximum one-side displacement is about 35 cm. Therefore, it was proposed that the designed shaft breach diameter throughout the salt interval would be increased for safety to by 40 cm.
4. Innovative construction of the shaft lining alongside the salt interval
Geological and engineering conditions related to the salt layer occurrence in the area of the GG-1 shaft under construction have imposed the lining design of special construction [3].
Due to the presence of anhydrite interlayers in the salt deposit, the decision was made to secure the salt side walls of the shaft breach with the rock bolts and steel mesh. The final lining throughout the salt section is designed to be made of five layers. Starting from the shaft breach side, there are a yielding backfilling layer, an external concrete backfilling, an external tubing ring, an internal concrete backfilling and an inner tubing ring, respectively.
The yielding backfilling layer is made of two-component foam obtained by mixing an aqueous solution of a phenol-formaldehyde resin and an aqueous solution of organic and inorganic acids with the total thickness of about 100 mm. Its function is to initial unload the lining, so that rock salt creeping will not lead to concrete structural damage during the initial phase of its bonding. The second function is to equalize the salt rock pressure on the lining to a circular-symmetrical level of the pressure. The yielding layer should be applied in one cycle.
The main supporting elements of the shaft lining are two columns of tubing rings made of spheroidal cast iron. The external ring is designed of the 9.3 m inner diameter, and the inner one of 7.5 m diameter. Each of the rings is backfilled with the layer of concrete type C50/60 and thickness of 0.42 m for the outer ring and 0.5 m for the inner ring. Both tubing columns will be placed on the base foot through assembly flanges. The final lining will be built from the bottom upwards, after applying the yielding foam layer on the shaft breach face.
Due to technological reasons, in the final lining the outer tubing ring will be installed in advance of the inner tubing ring by 0.6 m.
In order to preserve the nominal thickness of the yielding layer and both concrete backfilling layers, the minimum diameter of the shaft breach should be of 11.54 m. However, taking into account the fact of time lag between unveiling the salt walls and installing the final lining, the breach must be made of a diameter ensuring the nominal thicknesses of the lining layers. Based on the numerical simulation, it was determined that the shaft breach diameter should be of 11.94 m.
Summary
In the northern part of the copper ore deposit on the Fore-Sudetic Monocline the GG-1 shaft is under construction. It will be the deepest shaft in the LGOM Copper Basin so far. The characteristic feature of the rock mass surrounding the GG-1 shaft is the deepest depth of copper-bearing rocks among the currently being operated deposits as well as the presence of the rock salt layer with the considerable thickness at the depth of more than 1000 m in the Zechstein formations. Rheological properties of salt massif are the crucial factors deciding about the shaft stability and life-span of its lining over the salt section. The salt creep causes horizontal convergence of the shaft excavation. Following the shaft breach unveiling, the elastic creep process gradually goes into the steady-state flow. After reaching the dilatation threshold, the third phase of creeping takes place, i.e. rock damage. The presence of rock salt in a shaft profile determines the necessity of assessing the salt massif behavior following the shaft breach unveiling, until it will be secured with the final lining, as well as estimating the rock mass pressure. It is crucial to determine the proper diameter of the shaft breach, so that at the time of the final lining installation it has at least a nominal value.
The experience gained with the lining construction installed through the salt section in the SW-4 shaft was used to design the lining for the GG-1 shaft, distant from the
SW-4 shaft by 5 km. The parameters of the Burgers model were obtained using the Lavenberg-Marquardt method and numerical simulation, which allowed to determine the rate of salt flow in the "Kaźmierzów" deposit at various depths in the shaft. Because the function of the GG-1 shaft excludes shaft operation stoppage for a period of possible reconstruction of the salt section, which took place in the SW-4 shaft, a new design solution for the shaft lining was proposed. Designed the four-layer lining construction with the yielding foam backfilling is based on a force solution that will be able to fully transfer the pressure associated with the rheological flow of the salt rock mass. In the opinion of the authors, this lining solution will permanently protect the shaft excavation in a way that does not require its cyclical reconstruction and guarantees safe conditions for its operation until the deposit depletion in the mining area of "Głogów Głęboki-Przemysłowy".
References
[1] Fabich S. et al., 2009, Projekt obudowy w interwale solnym szybu SW-4 dla wariantu I – obudowa powłokowa (unpublished). KGHM CUPRUM Research and Development Centre, Wrocław.
[2] Fabich S. et al., 2016, Analiza porównawcza dla opracowania założeń optymalnego modelu wyrobiska udostępniającego złoże rudy miedzi w obszarach koncesyjnych KGHM Polska Miedź S.A.. Etap I – Analiza dotychczas stosowanych rozwiązań technologicznych oraz organizacyjnych w procesie wykonywania wyrobisk udostępniających złoża rudy miedzi w Polsce, ze wskazaniem elementów mających najistotniejszy wpływ na osiąganą wydajność (unpublished). I-MORE Project Report, KGHM CUPRUM Research and Development Centre, Wrocław.
[3] Fabich S. et al., 2017, Opracowania projektowe dla potrzeb budowy i głębienia szybu GG-1. Etap II – Projekt techniczny głębienia i obudowy szybu poniżej strefy mrożonej do głębokości 1131,65 m (unpublished). KGHM CUPRUM Research and Development Centre, Wrocław.
[4] Itasca Consulting Group, Inc. 2016, FLAC user’s guide. Fast Lagrangian Analysis of Continua Creep Material Models. Sixth Edition (FLAC Version 8.0). Minneapolis, Minnesota, USA.
