Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is ...Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the paleodepositional history of these lignite sequences. The lignites of Cambay basin dominantly comprise huminite maceral group （71.6%-86.3%） followed by liptinite （10.1%-19.3%） and inertinite （3.6%-11.0%） maceral groups. The mineral matter varies from 9.0% to 20.0%. The petrography based facies model indicates that these lignites have high values of gelification index （GI） and low tissue preservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajpardi and Vastan mines, the value of GI exceeded 10 which indicates a forest permanently flooded and the cause of pronounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier spells of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is specially indicated by the occurrence of funginite which normally thrives in the upper oxy- genated peatigenic layer and indicates prevalence of oxic conditions during plant deposition. Such conditions prevailed during a transgressive phase but there were intermittent fluvial activities also giving rise to supratidal flood plain as reflected in the form of associated carbonaceous shales in the basin.展开更多
The everyday fluctuations of temperature and humidity lead to fluctuation of stress on the stones constituting many constructions and produce in long term some kinds of fatigue damage. This paper investigates the comb...The everyday fluctuations of temperature and humidity lead to fluctuation of stress on the stones constituting many constructions and produce in long term some kinds of fatigue damage. This paper investigates the combined role of stone properties variability and environmental conditions on the generation and the amplification of stress variation and fatigue. Thus, the randomness and spatial variability 0fthe mechanical, thermal and hydraulic properties are taken into account in a finite elements model of typical stone wall masonry of Chambord Castle. The quantification of the impact of this spatial variability on the variability of generated stress is performed.展开更多
Ammonium oxalate treatment, previously extensively studied on limestone in the laboratory, was applied to powdering historical stonework （limestone） situated on the shoreline in the Mediterranean Island of Malta. Th...Ammonium oxalate treatment, previously extensively studied on limestone in the laboratory, was applied to powdering historical stonework （limestone） situated on the shoreline in the Mediterranean Island of Malta. This paper presents the results obtained from onsite testing that aimed at evaluating the treatment in terms of its aesthetic performance, the depth of treatment, the mechanical properties of the consolidated stone and the influence on water transport. To this end, the testing program included colorimetry, DRMS （drilling resistance measurement system） and water absorption through the contact sponge method. This study is Part One of the final phase of a wider research program which included two previous phases progressing from treating this same very porous stone type in a laboratory-based controlled environment to uncontrolled site conditions, seeking to quantify this treatment＇s effectiveness in the field. Results showed that onsite consolidation was achieved and that although some changes in colour and water absorption were brought about by the treatment, these were within acceptable tolerance limits. Besides carrying out these treatments and evaluations directly on the coast, this study anticipates further studies which will look at rural and urban sites where the types and concentrations of salts are expected to be different.展开更多
文摘Lignite samples collected from Vastan, Rajpardi and Tadkeshwar lignite mines of Cambay basin （Gujarat） were subjected to organic petrographic investigations and geochemical analyses and the data, thus generated, is used to reconstruct the paleodepositional history of these lignite sequences. The lignites of Cambay basin dominantly comprise huminite maceral group （71.6%-86.3%） followed by liptinite （10.1%-19.3%） and inertinite （3.6%-11.0%） maceral groups. The mineral matter varies from 9.0% to 20.0%. The petrography based facies model indicates that these lignites have high values of gelification index （GI） and low tissue preservation index revealing a continuous wet condition in the basin and a relatively slower rate of subsidence during the decay of organic matter. On several occasions, during the formation of seams in Tadkeshwar, Rajpardi and Vastan mines, the value of GI exceeded 10 which indicates a forest permanently flooded and the cause of pronounced degree of degradation. However, few sections in Tadkeshwar seam had relatively drier spells of environmental conditions due to fluctuation in the water table as revealed by moderately high content of inertinite macerals. This is specially indicated by the occurrence of funginite which normally thrives in the upper oxy- genated peatigenic layer and indicates prevalence of oxic conditions during plant deposition. Such conditions prevailed during a transgressive phase but there were intermittent fluvial activities also giving rise to supratidal flood plain as reflected in the form of associated carbonaceous shales in the basin.
文摘The everyday fluctuations of temperature and humidity lead to fluctuation of stress on the stones constituting many constructions and produce in long term some kinds of fatigue damage. This paper investigates the combined role of stone properties variability and environmental conditions on the generation and the amplification of stress variation and fatigue. Thus, the randomness and spatial variability 0fthe mechanical, thermal and hydraulic properties are taken into account in a finite elements model of typical stone wall masonry of Chambord Castle. The quantification of the impact of this spatial variability on the variability of generated stress is performed.
文摘Ammonium oxalate treatment, previously extensively studied on limestone in the laboratory, was applied to powdering historical stonework （limestone） situated on the shoreline in the Mediterranean Island of Malta. This paper presents the results obtained from onsite testing that aimed at evaluating the treatment in terms of its aesthetic performance, the depth of treatment, the mechanical properties of the consolidated stone and the influence on water transport. To this end, the testing program included colorimetry, DRMS （drilling resistance measurement system） and water absorption through the contact sponge method. This study is Part One of the final phase of a wider research program which included two previous phases progressing from treating this same very porous stone type in a laboratory-based controlled environment to uncontrolled site conditions, seeking to quantify this treatment＇s effectiveness in the field. Results showed that onsite consolidation was achieved and that although some changes in colour and water absorption were brought about by the treatment, these were within acceptable tolerance limits. Besides carrying out these treatments and evaluations directly on the coast, this study anticipates further studies which will look at rural and urban sites where the types and concentrations of salts are expected to be different.
