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1

Safety of Steel Arch Support Operation During Rock Bursts Under Explosive Atmosphere Conditions

Pytlik Andrzej, Frąc Witold

Studia Geotechnica et Mechanica

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2023

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Vol. 45, nr 2

144-157

EN

Methane and coal dust explosions are among the most common causes of disasters in hard coal mining. Therefore, it is important for occupational safety in hard coal mines operating under methane and coal dust explosion hazards to identify possible ignition sources, whether due to natural or technical factors. One technical source of ignition can be mechanical sparks generated during operation of mechanical equipment and high surface temperatures of equipment components during operation. This paper presents the methodology and results of thermal imaging and strength testing of roadway support elements under dynamic loading. The goal of the tests was to identify the potential explosive atmosphere ignition sources during the operation of the support under the conditions of rock bursts. The scope of testing encompassed the temperature measurements by means of thermal camera of friction prop and yielding support frame sliding joint elements at yield under dynamic impact loading (simulating a burst). Significant joint element heating and mechanical sparking was observed during the testing of arching yielding support frame sliding joints and straight friction prop joints as a result of friction at yield. Some of the aspects defined in standard PN-EN ISO80079-36:2016 include the maximum temperature T max =150°C for a surface that can accumulate a layer of coal dust. Tests of the friction joints have shown that during impact loading, numerous mechanical sparks are produced at the friction joints of sections of the steel prop, with the surface temperature of the sections starting from 169.6°C and reaching up to 234.1°C. During tests it was also to determined emissivites of the tested sliding joints constructed from V29-V32 secrions depending on corrosion products which consist in range 0.842-0.873. Such a high temperature can initiate an explosive mixture consisting of methane, air and coal dust.

2

Badania niezwiązanej mieszanki stabilizowanej georusztem o monolitycznych węzłach poddanej deformacjom rozluźniającym

Grygierek Marcin, Kalisz Piotr, Zięba Magdalena, Pytlik Andrzej

Materiały Budowlane

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2023

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nr 9

45--48

PL

W artykule przedstawiono badania dotyczące stosowania georusztów o sztywnych monolitycznych węzłach do wzmocnienia warstw wykonanych z mieszanek niezwiązanych. Celem badań było sprawdzenie skuteczności funkcji stabilizującej, którą przypisuje się georusztom współpracującym z ziarnami kruszywa, w warunkach osłabienia podłoża. Podłoże zostało osłabione przez rozluźnienie najniższej warstwy wykonanej z piasku, co symulowało oddziaływanie eksploatacji górniczej. Uzyskane wyniki potwierdziły, że wzmocnienia georusztem znacznie ograniczają degradację sztywności warstwy z niezwiązanej mieszanki poddanej deformacjom górniczym.

EN

The article presents the research works focus on geogrids with rigid monolithic nodes to reinforce layers made of unbound mixes. The aim of the research was to check the effectiveness of the stabilizing function, which is attributed to geogrids cooperating with aggregate grains, in conditions of subgrade weakening. The subgrade was weakened by loosening the lowest layer made of sand, which simulated mining impact. The obtained results confirmed that the reinforcement with a geogrid significantly reduces the degradation of the stiffness of the unbound mix layer subjected to mining deformations.

3

Comparative Shear Tests of Bolt Rods Under Static and Dynamic Loading

Pytlik Andrzej

Studia Geotechnica et Mechanica

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2020

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Vol. 42, nr 2

151--167

EN

This article presents the methodology and results of single shear tests of bolt rods under dynamic impact loading generated by means of a drop hammer. Comparative analysis was also performed for bolt rod load capacity, stress and shear work under static and dynamic (impact) loading. The developed method of single shear testing of bolt rods under impact loading makes it possible to obtain repeatable test results concerning maximum bolt rod shearing force, shear stress and shear work values. Comparative shear tests of four types of bolt rods under static and impact loading showed that the APB-type bolt rods made of AP770 steel, which was characterised by having the highest strength, exhibited the greatest shear work. AM22- type bolt rods exhibited a very similar work value. Though the AM22-type bolt rods made of A500sh steel demonstrated lower strength than the APB-type bolts, as well as a smaller diameter and cross section, they dissipated the impact energy better thanks to their higher plasticity. This could indicate the direction of optimisation for bolt rods in order to increase their impact strength. Mathematical relationships were also formulated for selected tests, describing the real single shear courses F d =f(t ) of bolts under impact loading. The obtained relationships could be applied in the load assessment process of bolt rods intended for use under roof caving, tremor and rock burst conditions.

4

Strength testing of rock and ground anchor rods under static and dynamic loads

Frąc Witold, Pytlik Andrzej, Pacześniowski Krzysztof

Mining – Informatics, Automation and Electrical Engineering

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2020

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R. 58, nr 2

71--78

EN

Various types of anchor rods are commonly used for rock mass and soil reinforcement, produced either as full-section steel rods or tubes with threads along their entire length, which are used for the injection of liquid binders. This paper presents the methodology and sample results of strength tests of self-drilling injection anchor rods with R32 rope threads. Such rods are used both in underground mining and in geoengineering under static and dynamic (impact) loads. The results of tests of injection micropiles with trapezoidal thread diameters in the range of T51–T111 mm, used mainly in geoengineering, are provided as well. This paper also presents the basic requirements for the fatigue loading of nails and injection micropiles used in geoengineering, based on standards and the European Assessment Document (EAD), applicable in the European Union.

PL

Do wzmacniania górotworu oraz gruntu powszechnie stosuje się różnego typu żerdzie kotwi wykonane zarówno w postaci stalowych prętów o pełnym przekroju, jak i rur z gwintem na całej długości, które służą do iniekcji spoiw płynnych. W artykule przedstawiono metodykę oraz przykładowe wyniki wytrzymałościowych badań żerdzi kotwi samowiercących iniekcyjnych z gwintem falistym R32. Tego typu żerdzie stosowane są zarówno w górnictwie podziemnym, jak i geoinżynierii, przy obciążeniu statycznym i dynamicznym – o charakterze impulsowym (udarowym). Przedstawiono również wyniki badań mikropali iniekcyjnych o średnicach gwintu o zarysie trapezowym z zakresu T51–T111 mm, stosowanych głównie w geoinżynierii. Na podstawie norm oraz dokumentu EAD (European Assessment Document), obowiązującego w Unii Europejskiej, w artykule przedstawiono także podstawowe wymagania w zakresie obciążeń zmęczeniowych, stawiane gwoździom i mikropalom iniekcyjnym stosowanym w geoinżynierii.

5

Badania wytrzymałościowe żerdzi kotwi górniczych i gruntowych przy obciążeniu statycznym i dynamicznym

Frąc Witold, Pytlik Andrzej, Pacześniowski Krzysztof

Mining – Informatics, Automation and Electrical Engineering

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2020

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R. 58, nr 2

79--86

PL

Do wzmacniania górotworu oraz gruntu powszechnie stosuje się różnego typu żerdzie kotwi wykonane zarówno w postaci stalowych prętów o pełnym przekroju, jak i rur z gwintem na całej długości, które służą do iniekcji spoiw płynnych. W artykule przedstawiono metodykę oraz przykładowe wyniki wytrzymałościowych badań żerdzi kotwi samowiercących iniekcyjnych z gwintem falistym R32. Tego typu żerdzie stosowane są zarówno w górnictwie podziemnym, jak i geoinżynierii, przy obciążeniu statycznym i dynamicznym – o charakterze impulsowym (udarowym). Przedstawiono również wyniki badań mikropali iniekcyjnych o średnicach gwintu o zarysie trapezowym z zakresu T51–T111 mm, stosowanych głównie w geoinżynierii. Na podstawie norm oraz dokumentu EAD (European Assessment Document), obowiązującego w Unii Europejskiej, w artykule przedstawiono także podstawowe wymagania w zakresie obciążeń zmęczeniowych, stawiane gwoździom i mikropalom iniekcyjnym stosowanym w geoinżynierii.

EN

Various types of anchor rods are commonly used for rock mass and soil reinforcement, produced either as full-section steel rods or tubes with threads along their entire length, which are used for the injection of liquid binders. This paper presents the methodology and sample results of strength tests of self-drilling injection anchor rods with R32 rope threads. Such rods are used both in underground mining and in geoengineering under static and dynamic (impact) loads. The results of tests of injection micropiles with trapezoidal thread diameters in the range of T51–T111 mm, used mainly in geoengineering, are provided as well. This paper also presents the basic requirements for the fatigue loading of nails and injection micropiles used in geoengineering, based on standards and the European Assessment Document (EAD), applicable in the European Union.

6

Research on the impact of forces and acceleration during the riding and braking of a suspended monorail

Tokarczyk Jarosław Andrzej, Rotkegel Marek, Pytlik Andrzej, Niedworok Andrzej

Archives of Mining Sciences

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2020

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Vol. 65, no. 2

399--414

EN

This article presents the results of experimental studies aimed at identifying the forces and acceleration during the riding and braking action of a suspended monorail. The tests were conducted under in situ conditions, in a dip-heading “B” ZG SILTECH in Zabrze. The paper also discusses a test stand, a metering system, and presents the impact of changes in speed on forces in slings of the suspended route. The measurements of selected parameters were performed for three variants: the route, the emergency haulage braking and the braking trolley set braking. The results include waveforms of forces in route slings, and acceleration values acting on the operator and transported load.

7

Experimental studies of static and dynamic steel arch support load capacity and sliding joint temperature parameters during yielding

Pytlik Andrzej

Archives of Mining Sciences

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2020

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Vol. 65, no. 3

469--491

EN

Difficult geological and mining conditions as well as great stresses in the rock mass result in significant deformations of the rocks that surround the workings and also lead to the occurrence of tremors and rock bursts. Yielding steel arch support has been utilised in the face of hard coal extraction under difficult conditions for many years, both in Poland and abroad. A significant improvement in maintaining gallery working stability is achieved by increasing the yielding support load capacity and work through bolting; however, the use of rock bolts is often limited due to factors such as weak roof rock, significant rock mass fracturing, water accumulation, etc. This is why research and design efforts continue in order to increase yielding steel arch support resistance to both static and dynamic loads. Currently, the most commonly employed type of yielding steel arch support is a support system with frames constructed from overlapping steel arches coupled by shackles. The yield of the steel frame is accomplished by means of sliding joints constructed from sections of various profiles (e.g. V, TH or U-type), which slip after the friction force is exceeded; this force is primarily dependent on the type of shackles and the torque of the shackle screw nuts. This article presents the static bench testing results of ŁP10/V36/4/A, ŁP10/V32/4/A and ŁP10/V29/4/A yielding steel arch support systems formed from S480W and S560W steel with increased mechanical properties. The tests were conducted using 2 and 3 shackles in the joint, which made it possible to compare the load capacities, work values and characteristics of various types of support. The following shackle screw torques were used for the tests: Md = 500 Nm – for shackles utilised in the support constructed from V32 and V36 sections. Md = 400 Nm – for shackles utilised in the support constructed from V29 sections. The shackle screw torques used during the tests were greater compared to the currently utilised standard shackle screw torques within the range of Md = 350-450 Nm. Dynamic testing of the sliding joints constructed from V32 section with 2 and 3 shackles was also performed. The SD32/36W shackles utilised during the tests were produced in the reinforced versions and manufactured using S480W steel. Since comparative testing of a rock bolt-reinforced steel arch support system revealed that the bolts would undergo failure at the point of the support yield, a decision was made to investigate the character of the dynamics of this phenomenon. Consequently, this article also presents unique measurement results for top section acceleration values registered in the joints during the conduction of support tests at fullscale.Filming the yield in the joint using high-speed video and thermal cameras made it possible to register the dynamic characteristics of the joint heating process at the arch contact point as well as the mechanical sparks that accompanied it. Considering that these phenomena have thus far been poorly understood, recognising their significance is of great importance from the perspective of occupational safety under the conditions of an explosive atmosphere, especially in the light of the requirements of the new standard EN ISO 80079-36:2016, harmonised with the ATEX directive.

8

Tests of steel arch and rock bolt support resistance to static and dynamic loading induced by suspended monorail transportation

Pytlik Andrzej

Studia Geotechnica et Mechanica

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2019

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Vol. 41, nr 2

81--92

EN

At present, the suspended monorail systems constitute a very common means of transportation in the Polish hard coal mines. The main advantages of the suspended monorail include the independence of the route from the working floor surface irregularities and the possibility to transport cargo of significant mass and size. The masses and dimensions of machines and devices transported via monorail have increased considerably in recent times. This particularly concerns the transport of longwall system elements. In Poland, the maximum speed of suspended monorail travel is 2 m/s. Due to the fact that preparations are currently underway to increase the maximum speed above 2 m/s, it is necessary to inspect what influence it will have on work safety and mining support stability. Current operational experience and tests have shown that dynamic loads induced by the suspended monorail transportation have a significant influence on the roadway support stability, working protection durability and on the monorail operators. This is particularly true during the emergency braking of a suspended monorail by means of a braking trolley, where the overloads reach 3g. Bench tests of the selected steel arch and rock bolt support elements utilised in the Polish hard coal mines were conducted in order to determine the resistance of steel arch and rock bolt supports to static and dynamic loads. The article presents the results of the tests conducted on a steel arch support in the form of the sliding joints of an ŁP/V29 yielding roadway support, which is commonly employed in the Polish hard coal mines. Tests of elements of the threaded bolts with trapezoidal threads over the entire rod length were conducted as well. The conducted strength tests of steel arch and rock bolt support elements under static and dynamic loading have shown that dynamic loading has decisive influence on the support’s retaining of its stability. Support element stability decreases along with the increase of the impact velocity. This concerns both the steel arch support and the rock bolt support.

9

Monitorowanie obciążeń w obudowie łukowej z zastosowaniem przetworników strunowych

Woszczyński Mariusz, Tokarczyk Jarosław, Mazurek Krzysztof, Pytlik Andrzej

Mining – Informatics, Automation and Electrical Engineering

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2019

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R. 57, nr 1

59--69

PL

W artykule zaprezentowano koncepcję pomiaru obciążenia i geometrii obudowy wyro-biska korytarzowego z zastosowaniem przetworników z drgającą struną oraz przetworników linkowych. W ramach realizacji projektu europejskiego INESI przeprowadzono badania laboratoryjne, a następnie badania stanowiskowe kompletnych odrzwi obudowy łukowej pod obciążeniem. Wyniki odkształcenia uzyskane z przetworników strunowych są porównywalne z wynikami uzyskanymi z tensometrów. Zaprezentowano również obliczenia wytrzymałościowe MES, które wykazały dużą zgodność z wynikami badań stanowiskowych.

10

Monitoring of loads in arch support with wire strain gauge

Woszczyński Mariusz, Tokarczyk Jarosław, Mazurek Krzysztof, Pytlik Andrzej

Mining – Informatics, Automation and Electrical Engineering

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2019

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R. 57, nr 1

48--58

EN

A concept of measuring the load and geometry of a roadway support with the use of vibrating wire strain gauges and draw-wire sensors is presented. Laboratory and in-situ tests of complete frames of arch supports under load were carried out within the INESI project. The deformations recorded by the vibrating wire strain gauges are similar to those recorded by the strain gauges. FEM strength calculations (which were similar to the results from the stand tests) were also presented.

11

Comparative bench testing of steel arch support systems with and without rock bolt reinforcements

Pytlik Andrzej

Archives of Mining Sciences

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2019

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Vol. 64, no. 4

747--764

EN

The mining of hard coal deposits at increasingly greater depth leads to an increase in hazards related to the loss of stability of steel arch supports as a result of excessive static and dynamic loads. Camber beam reinforcement via rockbolting is often utilised in order to improve the stability of the yielding steel arch support.This article presents the results of comparative bench tests of the ŁP10/V36-type steel arch support, tested with and without reinforcement by means of self-drilling bolts with drunken R25 threads, using short joists formed from V32 and V25 sections. It also presents the results of comparative tests of the ŁPP10/4/V29/I-type steel arch support, tested with and without reinforcement by means of rock bolts with trapezoidal Tr22/13 threads, using short joists formed from V25 sections. The obtained test results, in the form of load courses and work values of the steel arch and mixed (arches and rock bolts) support systems, demonstrate that the utilisation of mixed support may significantly improve the stability of workings, particularly immediately after they are driven. A mixed support system quickly achieves its maximum load capacity together with a significant increase in its work value. It may thus prevent the stratification of the rocks surrounding the working, and therefore better utilise the self-supporting capacity of the rock mass. As evidenced by the test results, the mixed support work may be as much as 3.5 times as great compared to the steel arch support at the beginning of the height reduction process initiated by loading – i.e. until its reduction by a presupposed value of 100 mm.

PL

Eksploatacja pokładów węgla kamiennego na coraz większych głębokościach powoduje wzrost zagrożeń związanych z utratą stateczności podporowej obudowy górniczej w wyniku nadmiernych obciążeń statycznych i dynamicznych. W celu poprawy stateczności podatnych odrzwi obudowy podporowej często stosuje wzmocnienie odrzwi poprzez przykotwienie łuku stropnicowego. W artykule przedstawiono wyniki stanowiskowych badań porównawczych odrzwiowej obudowy podporowej typu ŁP10/V36, badanej bez wzmocnienia oraz ze wzmocnieniem za pomocą kotwi samo- wiercących z gwintem falistym R25, przy użyciu krótkich podciągów wykonanych z kształtownika V32 oraz V25. Przedstawiono również wyniki badań porównawczych odrzwiowej obudowy podporowej typu ŁPP10/4/V29/I, badanej bez wzmocnienia oraz ze wzmocnieniem za pomocą kotwi z gwintem trapezowym Tr22/13, przy użyciu krótkich podciągów wykonanych z kształtownika V25.Uzyskane wyniki badań w postaci przebiegów obciążania oraz wartości pracy obudowy podporowej i podporowo-kotwiowej wykazują, że stosowanie obudowy podporowo-kotwiowej może znacząco poprawić stateczność wyrobiska górniczego szczególnie zaraz po jego wydrążeniu. Dzięki temu, że obudowa podporowo-kotwiowa szybko uzyskuje swoją maksymalną nośność przy znaczącym wzroście wartości pracy może zapobiegać rozwarstwianiu skał wokół wyrobiska, a przez to lepiej wykorzystać samonośność górotworu. Jak wykazują wyniki badań, praca W obudowy podporowo-kotwiowej może być nawet ponad 3.5-krotnie większa od obudowy podporowej na początku procesu jej obniżania pod wpływem obciążenia – to znaczy do czasu jej obniżenia o umowną wartość 100 mm.