SPECIFIČNA POTROŠNJA ENERGIJE KOPANJA MATERIJALA BAGEROM PRI DOBIVANJU TEHNIČKO-GRAĐEVNOGA KAMENA

A hydraulic excavator is widely used in crushed stone quarries to perform many different operations. Previous research on material handling by excavators is most often based on laboratory testing and observation of soil materials and the digging forces in them. These results are very difficult to transfer to fieldwork during the quarrying process. Therefore, in this work, the energy consumption of an excavator while working in typical materials for a crushed stone quarry was investigated. The field measurements were performed on overburden, blasted rock material, boulders, and two different crushed materials. Energy consumption was observed only during the portion of the cycle in which the bucket digs the material. In this way, the energy consumption was mainly related to the properties of the material. The highest energy consumption was found for blasted rock material, lower in overburden, and the lowest for boulders and crushed materials. These results are important for organizing an optimal distribution of machines according to the work tasks in the quarry and ultimately for energy savings.Hidraulični bager ima široku primjenu u obavljanju različitih poslova na kamenolomima tehničko-građevnoga kamena. Dosadašnja istraživanja rada bagera u različitim materijalima najčešće su bazirana na laboratorijskim ispitivanjima provedenim na uzorcima tla te na promatranju sila kopanja u njima. Takve rezultate vrlo je teško primijeniti na realan rad bagera u kamenolomu. U sklopu ovoga istraživanja provedeno je ispitivanje potrošnje energije prilikom rada bagera na tipičnim materijalima u kamenolomu. Terenska mjerenja izvedena su na otkrivci, odminiranoj stijenskoj masi, blokovima i dvjema različitim frakcijama drobljenoga materijala. Potrošnja energije promatrana je samo tijekom dijela ciklusa u kojemu lopata kopa materijal. Na taj način potrošnja energije najviše ovisi o svojstvima materijala. Najveća potrošnja energije izmjerena je pri radu u odminiranoj stijenskoj masi, nešto niža u otkrivci, zatim u blokovima te najniža u drobljenome materijalu. Ovi rezultati važni su za organizaciju optimalne raspodjele strojeva po radnim zadatcima u kamenolomu te u konačnici za uštedu energije

HISTORICAL OCCURENCE OF LIQUEFACTION IN ZAGREB AREA AND ESTIMATION OF REOCCURENCE IN CASE OF ANOTHER STRONG EARTHQUAKE

Tijekom Velikog zagrebačkog potresa iz 1880. na šest lokacija u okolici Zagreba primijećeni su pokazatelji likvefakcije u vidu pojave "muljnih vulkana" (engl.: sand boils) nastalih istjecanjem podzemne vode na površinu. Likvefakcija je po definiciji fenomen kod kojeg se čvrstoća i stabilnost saturiranih nekoherentnih tala smanjuju, do hidrauličkog sloma, pod utjecajem potresa ili nekog drugog dinamičkog opterećenja. Čimbenik važan za pojavu likvefakcije je stanje zbijenosti sedimenata koje dobrim dijelom zavisi od njihove starosti. Određivanjem apsolutne starosti fosiliziranih stabala nađenih u sedimentima savskog aluvija kod Zagreba te na osnovi terenskih ispitivanja zbijenosti tla zaključuje se da je pri potresu magnitude ≥ 6,3 na zagrebačkom području moguće ponovo očekivati pojavu likvefakcije.During the Great Zagreb\u27s earthquake in 1880 consequences of the liquefaction have been detected at six sites in the vicinity of Zagreb as the occurrence of sand boils. Liquefaction takes place when loosely packed, water-logged sediments near the ground surface lose their strength in response to strong ground shaking. During the liquefaction, due to pore pressure buildup, water may be forced to the surface carrying sand particles through volcano-like sand boils. Important factor for liquefaction occurrence is the state of soil densification which relates to geological age of deposits. Results of the absolute dating of fossilized trees found in Sava\u27s alluvium in the vicinity of Zagreb and the results of the penetration tests show that another earthquake with magnitude ≥ 6.3 can provoke liquefaction once again

THE IMPACT OF LABORATORY AIR TEMPERATURE AND RELATIVE HUMIDITY ON BENTONITE WATER ABSORPTION CAPACITY

Bentonit kao mineralna komponenta bentonitnih tepiha ima važna fizička i kemijska svojstva koja mu osiguravaju vrlo malu hidrauličku propusnost. Glavni sastojak bentonita je mineral glina naziva montmorillonit koji vrlo malu propusnost može zahvaliti sposobnosti bubrenja. Ležišta bentonita rasprostiru se posvuda po svijetu, međutim, samo mali broj njih zadovoljava uvjete kvalitete i trajnosti potrebne za upotrebu u brtvenim barijerama. Ovisno o mjestu ugradnje i namjeni, bentonitni tepisi moraju zadovoljiti određene kriterije. Sukladnost s propisanim kriterijima potvrđuje se različitim laboratorijskim postupcima. U te postupke ubrajaju se i pokusi za ispitivanje indeksnih pokazatelja (indeks slobodnog bubrenja, indeks gubitka fluida i kapacitet upijanja vode). U ovom radu prikazana su zapažanja o utjecaju temperature i relativne vlažnosti prostora u kojemu se provodi ispitivanje na dobivene vrijednosti kapaciteta upijanja, jednog od kriterija koji bentonit mora zadovoljiti prilikom kontrole kvalitete i trajnosti mineralne komponente bentonitnih tepiha.Bentonite, which is a mineral component of geosynthetic clay liners, has important physical and chemical properties that ensure very small hydraulic permeability. The main component of bentonite is a clay mineral called sodium montmorillonite whose very low permeability is due to its ability to swell. The deposits of bentonite are spread all over the world, however, only a very small number of those deposits satisfies all the quality and durability demands that must be met if the bentonite is to be used in the sealing barriers. Depending on the location of installation and their purpose, geosynthetic clay liners must meet certain requirements. Their compatibility with the prescribed criterion is confirmed through various laboratory procedures. Amongst them are tests examining the index indicators (free swell index, fluid loss index, and water absorption capacity). This paper presents results regarding the impact of laboratory air temperature and relative humidity of the testing area on the water absorption capacity. This is one of the criteria that bentonite must satisfy during the quality and durability control of the mineral component of geosynthetic clay liner

CHARACTERIZATION OF BENTONITE FOR ENGINEERED BARRIER SYSTEMS IN RADIOACTIVE WASTE DISPOSAL SITES

Inženjerske barijere prisutne su u odlagalištima radioaktivnog otpada kako bi se osigurala bolja izolacija te zaštita ljudi i biosfere od opasnog ionizirajućeg zračenja radioaktivnog otpada. Funkcija brtvljenja osigurava se uglavnom upotrebom cementa ili gline (bentonita). Kontrola kvalitete gline provodi se postupcima uobičajenim za ispitivanje materijala koji se ugrađuju u brtvene barijere bilo kojeg inženjerskog zahvata. Jedina je razlika u kriterijima koje glina mora zadovoljiti. Propisana svojstva glina ovise također i o vrsti matične stijene. U članku su opisana svjetska iskustva u zbrinjavanju različitih vrsta radioaktivnog otpada. Detaljnije su opisani standardni postupci kontrole kvalitete bentonitih glina koje se koriste kao brtvene barijere u odlagalištima radioaktivnog otpada, te neka vlastita iskustva i rezultati ispitivanja u provedbi postupaka za određivanje indeksnih pokazatelja (indeks slobodnog bubrenja, kapacitet upijanja vode, granice plastičnosti) te ispitivanja hidrauličke propusnosti bentonita.Engineered barrier systems are used in radioactive waste disposal sites in order to provide better protection of humans and the environment from the potential hazards associated with the radioactive waste disposal. The engineered barrier systems usually contain cement or clay (bentonite) because of their isolation properties and long term performance. Quality control tests of clays are the same for all engineering barrier systems. Differences may arise in the required criteria to be met due for different application. Prescribed clay properties depend also on the type of host rocks. This article presents radioactive waste management based on best international practice. Standard quality control procedures for bentonite used as a sealing barrier in radioactive waste disposal sites are described as some personal experiences and results of the index tests (free swelling index, water adsorption capacity, plasticity limits) and hydraulic permeability of bentonite

LABORATORY TESTING OF BENTONITE CLAYS FOR LANDFILL DESIGN AND CONSTRUCTION

Temeljni i pokrovni brtveni sustavi sastavni su elementi svakog odlagališta. Najčešće se izvode kao klasični sustavi od zbijene gline točno određenih svojstava (CCL – compacted clay liner) ili korištenjem nekog od alternativnih rješenja kao što su: bentonitni tepisi (GCL – geosynthetic clay liner), bentonitom poboljšana tla (BES – bentonite enhanced soils), te mješavine glina s polimerima. Prateći svjetske trendove, i u Hrvatskoj se već više godina primjenjuju bentonitni tepisi u odlagalištima otpada. Ovisno o mjestu ugradnje i namjeni, bentonitni tepisi moraju zadovoljiti različite kriterije. Sukladnost s propisanim kriterijima potvrđuje se različitim laboratorijskim postupcima. U ovom radu prikazani su rezultati ispitivanja posmične čvrstoće i kemijske kompatibilnosti bentonitnih tepiha, te probna ispitivanja hidrauličke propusnosti na uzorcima kaolinske gline.Top and bottom liners are one of the key construction elements in every landfill. They are usually made as compacted clay liners (CCLs) composed of several layers of compacted clay with strictly defined properties or by the use of alternative materials such as: GCL – geosynthetic clay liner, BES – bentonite enhanced soils or bentonite/polymer mixtures. Following the state of the art experiences in the world, GCLs are used in Croatian landfills for several years, as well. Depending upon the location and the obeying function, GCLs have to fulfill certain conditions. A legislated compatibility criterion has to be proven by various laboratory tests. In the paper are presented the results of direct shear and chemical compatibility tests of GCLs as well as the results of permeability measurement of kaolin clay

THE IMPACT OF LABORATORY AIR TEMPERATURE AND RELATIVE HUMIDITY ON BENTONITE WATER ABSORPTION CAPACITY

Bentonit kao mineralna komponenta bentonitnih tepiha ima važna fizička i kemijska svojstva koja mu osiguravaju vrlo malu hidrauličku propusnost. Glavni sastojak bentonita je mineral glina naziva montmorillonit koji vrlo malu propusnost može zahvaliti sposobnosti bubrenja. Ležišta bentonita rasprostiru se posvuda po svijetu, međutim, samo mali broj njih zadovoljava uvjete kvalitete i trajnosti potrebne za upotrebu u brtvenim barijerama. Ovisno o mjestu ugradnje i namjeni, bentonitni tepisi moraju zadovoljiti određene kriterije. Sukladnost s propisanim kriterijima potvrđuje se različitim laboratorijskim postupcima. U te postupke ubrajaju se i pokusi za ispitivanje indeksnih pokazatelja (indeks slobodnog bubrenja, indeks gubitka fluida i kapacitet upijanja vode). U ovom radu prikazana su zapažanja o utjecaju temperature i relativne vlažnosti prostora u kojemu se provodi ispitivanje na dobivene vrijednosti kapaciteta upijanja, jednog od kriterija koji bentonit mora zadovoljiti prilikom kontrole kvalitete i trajnosti mineralne komponente bentonitnih tepiha.Bentonite, which is a mineral component of geosynthetic clay liners, has important physical and chemical properties that ensure very small hydraulic permeability. The main component of bentonite is a clay mineral called sodium montmorillonite whose very low permeability is due to its ability to swell. The deposits of bentonite are spread all over the world, however, only a very small number of those deposits satisfies all the quality and durability demands that must be met if the bentonite is to be used in the sealing barriers. Depending on the location of installation and their purpose, geosynthetic clay liners must meet certain requirements. Their compatibility with the prescribed criterion is confirmed through various laboratory procedures. Amongst them are tests examining the index indicators (free swell index, fluid loss index, and water absorption capacity). This paper presents results regarding the impact of laboratory air temperature and relative humidity of the testing area on the water absorption capacity. This is one of the criteria that bentonite must satisfy during the quality and durability control of the mineral component of geosynthetic clay liner

Residues Management within the National Program for the Implementation of the Strategy for the Management of Radioactive Waste, Disused Sources and Spent Nuclear Fuel of the Republic of Croatia

Donošenjem Nacionalnog programa provedbe Strategije zbrinjavanja radioaktivnog otpada, iskorištenih izvora i istrošenog nuklearnog goriva, Vlada Republike Hrvatske je ratificirala Strategiju koja dijelom određuje gospodarenje reziduima. S obzirom na važeću legislativu bit će nužno regulatorno modificirati trenutačne i predvidjeti buduće rudarske i druge industrijske aktivnosti u kojima nastaju rezidui i pri kojima se manipulira reziduima. U radu se daje detaljan pregled legislative te preporuka i smjernica, u skladu s posljednjim dostignućima, za gospodarenje postojećim i budućim odlagalištima i mjestima za privremeno pohranjivanje rezidua. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.By adopting the National Program for the Implementation of the Strategy for the Management of Radioactive Waste, Disused Sources and Spent Nuclear Fuel, the Government of the Republic of Croatia has ratified the Strategy, which partly defines the management of residues. Given the current legislation, it will be necessary to regulate modifications of the current as well as predict future mining and other industrial activities in which residues appear and are manipulated with. This paper gives a detailed review of relevant legislation, and state of the art recommendations and guidelines for the management of existing and future disposal sites and places for temporary storage of residues. This work is licensed under a Creative Commons Attribution 4.0 International License

The impact of swelling behaviour of bentonite on its mechanical properties : doctoral thesis

Glinene geosintetičke barijere su tvornički proizvedene hidrauličke barijere, koje se sastoje od mineralne i geosintetičke komponente. Mineralna komponenta najčešće je bentonitna glina, koja pripada skupini bubrivih tala. Tijekom procesa bubrenja dolazi do promjene njenih mehaničkih svojstava. Svrha je ovog istraživanja utvrditi utjecaj bubrenja na mehanička svojstva bentonitne gline. Za istraživanja je odabrana Volclay bentonitna glina u granulama, mineraloškog sastava: montmorillonit 80-85%, kristobalit oko 5%, kvarc oko 5%, plagioklasi 5%. Indeksni pokazatelji bentonitne gline iznosili su: granica tečenja 437,0%, granica plastičnosti 52,86%, specifična površina 700 m2/g i kapacitet ionske izmjene 88,63+/-6,51 meq/100g. Povezanost bubrenja i promjene vlažnosti s promjenama posmične čvrstoće i parametara posmične čvrstoće istraživana je u uređaju za izravni posmik. Pri tome su u serijama ispitivanja, kod različitih normalnih naprezanja (50, 100 i 200 kPa) mijenjana vremena hidratacije (7, 14 i 21 dan) simulirajući različite stupnjeve bubrenja bentonitne gline. Dugotrajnim pokusima bubrenja u edometru pri različitim normalnim naprezanjima (50, 100 i 200 kPa) definirana je krivulja bubrenja bentonitne gline. Povezanost bubrenja s konsolidacijskim i hidrauličkim svojstvima istraživana je u edometru i troosnom uređaju. Za usporedbu konsolidacijskog ponašanja bentonitne gline pri različitim vrstama opterećenja, osim u edometru, konsolidacijska svojstva ispitana su i u uređaju za troosni posmik pri izotropnoj kompresiji. Ispitivanja hidrauličkih svojstava provedena su u troosnom uređaju pri različitim srednjim vrijednostima efektivnih naprezanja (42,5; 92,5; 193,6 i 291,0 kPa) u uvjetima potpune zasićenosti uzorka. Pokusi bubrenja pokazali su da je bubrenje bentonitne gline dugotrajan proces. Završetak primarnog bubrenja postiže se nakon 31 dana neovisno o intenzitetu normalnog naprezanja. Nakon završetka primarnog bubrenja nastupila je faza sekundarne kompresije. Ispitivanja čvrstoće pokazuju da dolazi do smanjenja kohezije s produljenjem hidratacije bentonitne gline. Kut trenja se hidratacijom (od 7 do 14 dana) povećava. Produljenjem hidratacije nakon 14 dana nema značajnije promjene vrijednosti kuta trenja. Na krivulji odnosa završne vlažnosti i posmične čvrstoće vidljiva je promjena nagiba krivulje kod raspona završnih vlažnosti od 60 do 90%. Navedeno odgovara postojećim spoznajama o promjeni nagiba karakteristične krivulje retencije vode kod usisnih naprezanja od 0,4 do 1 MPa. Navedeni odnosi prezentirani su u svjetlu pretpostavljenih promjena u mikrostrukturi bentonitne gline tijekom bubrenja odnosno pojavom dvostrukih difuznih slojeva.Clay geosynthetic barriers are manufactured hydraulic barriers consisting of mineral and geosynthetic components. The mineral component is usually bentonite clay which belongs to the group of swelling soils. During the swelling process properties of clay are changing. The purpose of this study is to determine correlation between mechanical properties of the bentonite clay and its swelling behavior. The research was conducted on the granular bentonite clay Volclay. X-ray powder diffraction showed that the bentonitne clay contains 80-85% of montmorillonite, ~5% of cristobalite, ~5% of quartz and ~5% of plagioclase. Bentonite clay properties were as follows: liquid limit 437.0%, plastic limit 52.86%, specific surface area 700 m2/g and CEC 88.63+/-6.51 meq/100g. The influence of swelling on the bentonitne clay shear strength was studied in the direct shear device. During this process, hydration times were changed in a series of tests at different normal stresses (50, 100 and 200 kPa; 7, 14 and 21 days) simulating bentonite clay swelling. The swelling curves of bentonite clay were defined by the long-term oedometar tests at different normal stresses (50, 100 and 200 kPa). The impact of swelling on the bentonitne clay consolidation and hydraulic properties were studied in oedometer device and triaxial device under isotropic compression conditions. Bentonite clay hydraulic properties were studied in triaxial device under different mean values of effective stress (42.5; 92.5; 193.6 and 291.0 kPa) in saturated conditions. Demineralized water was used as the test fluid. Swelling tests showed that the bentonite clay swelling is a long-term process. Completion of the primary swelling phase is reached after 31 days regardless of the intensity of the normal stress. After completion of the primary phase, secondary compression phase started. Shear tests show a significant reduction in cohesion with the extension of the hydration of bentonite clay. Friction angle with hydration (from 7 to 14 days) increases. There is no significant change in the value of the friction angle by extending hydration after 14 days. On the final water content-shear strength curves in the semi-log diagram, the inclination of the curves decreases with final water content decrease. Change in curve inclination is noticeable in the final water content decrease range from 60 to 90%. This corresponds to the bentonitne clay water retention characteristic curves inclination changes under suction stresses from 0.4 to 1 MPa. The shear strength properties during swelling process are linked to the bentonitne clay microstructure features, and diffuse double-layer appearance