The Litang fault(LTF),located in the southeast of the Qinghai-Tibetan Plateau,is known for its high level of present-day seismicity,whereas its Pleistocene activity has been scarcely documented.This study focused on a...The Litang fault(LTF),located in the southeast of the Qinghai-Tibetan Plateau,is known for its high level of present-day seismicity,whereas its Pleistocene activity has been scarcely documented.This study focused on a tract of banded travertine deposits precipitated from thermal waters along the NW–SE-trending LTF trace.The role of travertine deposits in recording neotectonic activity has been studied by identifying their internal structure.Typical soft-sediment deformation structures observed within the banded travertines include micro folds,liquefied breccia,and liquefied diapirs.These deformed structures,which are restricted to a single unit separated unconformably by undeformed layers,can be traced for tens of meters,indicating that they were formed by seismic shaking triggered by LTF activity.The deformation of the banded travertine layers is attributed to the combined effects of seismic shaking,liquefaction,and fluidization,and it can be related to a paleo earthquake event with a magnitude of MS>5.The U-series ages obtained from the banded travertine deposits perturbed by the earthquakes are in the range of 130.59–112.94 ka,indicating an important fault-assisted neotectonic activity that occurred during the Middle–Late Pleistocene.Analysis of such structures,in combination with the use of U-series dating methods,can yield a reliable timing of neotectonic activity and provide new evidence for under-standing the seismotectonic setting of the Litang area.展开更多
Uniaxial Compressive Strength (UCS) and modulus of elasticity (E) are the most important rock parameters required and determined for rock mechanical studies in most civil and mining projects. In this study, two mathem...Uniaxial Compressive Strength (UCS) and modulus of elasticity (E) are the most important rock parameters required and determined for rock mechanical studies in most civil and mining projects. In this study, two mathematical methods, regression analysis and Artificial Neural Networks (ANNs), were used to predict the uniaxial compressive strength and modulus of elasticity. The P-wave velocity, the point load index, the Schmidt hammer rebound number and porosity were used as inputs for both meth-ods. The regression equations show that the relationship between P-wave velocity, point load index, Schmidt hammer rebound number and the porosity input sets with uniaxial compressive strength and modulus of elasticity under conditions of linear rela-tions obtained coefficients of determination of (R2) of 0.64 and 0.56, respectively. ANNs were used to improve the regression re-sults. The generalized regression and feed forward neural networks with two outputs (UCS and E) improved the coefficients of determination to more acceptable levels of 0.86 and 0.92 for UCS and to 0.77 and 0.82 for E. The results show that the proposed ANN methods could be applied as a new acceptable method for the prediction of uniaxial compressive strength and modulus of elasticity of intact rocks.展开更多
Objective One of major challenges in paleoenvironmental reconstruction using travertine in the Huanglong area is whether one can accurately determinate the age of travertine through high-precision and high-resolution...Objective One of major challenges in paleoenvironmental reconstruction using travertine in the Huanglong area is whether one can accurately determinate the age of travertine through high-precision and high-resolution dating techniques. Previous works of 14C or ESR chronology, however, have shown that the variation of deposition ages of travertine was displayed inconsistent with each other even conflict. For instance, （1） The oldest travertine age （80 ka） located in the middle of this travertine succession is departure from sequential deposition; （2） Top or boundary ages in this sedimentary section, even with the same dating method （14C）, are three times errors, moreover, the age of the depositional sequence is not continuous. We report here the U230Th ages in lowest boundary of travertine in Dawanzhangjia Valley, Huanglong, China, to discuss the effectiveness of U-series dating for cold-water travertine and the significance of age for vicissitude of paleoenvironment.展开更多
1 Introduction Dogai Coring is a name of lake lied in the northern Tibet.There are a series of modern salt springs and theies travertines.All of salt springs have an anomaly of potassium,implying that springs water ma...1 Introduction Dogai Coring is a name of lake lied in the northern Tibet.There are a series of modern salt springs and theies travertines.All of salt springs have an anomaly of potassium,implying that springs water may dissolve evaporites from deep bed formation,which includes halite展开更多
Travertine deposited around the Niangziguan karst springs was used as a new type of paleoclimate record in this study. Five stages of climate change in northern China from 200± ka to 36± ka before the presen...Travertine deposited around the Niangziguan karst springs was used as a new type of paleoclimate record in this study. Five stages of climate change in northern China from 200± ka to 36± ka before the present (B. P.) were reconstructed using the 18O and 13C isotope record of the travertine. Tendency of the change was towards a more arid climate. Coupling the temporal-spatial evolution of the springs with climate change, the hydrogeological evolution could be divided into four major periods since middle Pleistocene: (1)No spring period; (2)The initial period of spring outcropping as the predominant way of discharge; (3)The culmination period of spring development; and (4)The spring discharge attenuation period. The attenuation is partly related to the decrease of recharge as a result of the dry climate after 90±kaBP.展开更多
Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones. Therefore, determining the optimum sawing conditions for a particular stone is of ma...Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones. Therefore, determining the optimum sawing conditions for a particular stone is of major importance in the natural stone-processing industry. An experimental study was carried out utilizing a fully instrumented block-cutter to investigate the sawing performances of five different types of travertine blocks during cutting with a circular diamond saw. The sawing tests were performed in the down-cutting mode. Performance measurements were determined by measuring the cutting speed and energy consumption. Then, specific energy was determined. The one main cutting parameter, cutting speed, was varied in the investigation of optimum cutting performance. Furthermore, some physico-mechanical properties of file travertine blocks were determined in the laboratory. As a result, it is found that the energy consumption （specific energy） of block cutting machines is highly affected by cutting speed. It is determined that specific energy value usually decreases when cutting speed increases. When the cutting speed is higher than the determined value, the diamond saw can become stuck in the travertine block; this situation can be a problem for the block-cutting machine. As a result, the optimum cutting speed obtained for the travertine mines examined is approximately 1.5-2.0 m/min.展开更多
基金This work is supported financially by Spark Program of Earthquake Sciences,China Earthquake Administration(XH202301Y and XH23048C)State Key Laboratory of Earthquake Dynamics,Institute of Geology,CEA(LED2020B02)+1 种基金Lhasa National Geophysical Observation and Research Station(NORSLS21-04)Earthquake Science and Technology Special Project of Sichuan Earthquake Agency(LY2205 and LY2206).
文摘The Litang fault(LTF),located in the southeast of the Qinghai-Tibetan Plateau,is known for its high level of present-day seismicity,whereas its Pleistocene activity has been scarcely documented.This study focused on a tract of banded travertine deposits precipitated from thermal waters along the NW–SE-trending LTF trace.The role of travertine deposits in recording neotectonic activity has been studied by identifying their internal structure.Typical soft-sediment deformation structures observed within the banded travertines include micro folds,liquefied breccia,and liquefied diapirs.These deformed structures,which are restricted to a single unit separated unconformably by undeformed layers,can be traced for tens of meters,indicating that they were formed by seismic shaking triggered by LTF activity.The deformation of the banded travertine layers is attributed to the combined effects of seismic shaking,liquefaction,and fluidization,and it can be related to a paleo earthquake event with a magnitude of MS>5.The U-series ages obtained from the banded travertine deposits perturbed by the earthquakes are in the range of 130.59–112.94 ka,indicating an important fault-assisted neotectonic activity that occurred during the Middle–Late Pleistocene.Analysis of such structures,in combination with the use of U-series dating methods,can yield a reliable timing of neotectonic activity and provide new evidence for under-standing the seismotectonic setting of the Litang area.
文摘Uniaxial Compressive Strength (UCS) and modulus of elasticity (E) are the most important rock parameters required and determined for rock mechanical studies in most civil and mining projects. In this study, two mathematical methods, regression analysis and Artificial Neural Networks (ANNs), were used to predict the uniaxial compressive strength and modulus of elasticity. The P-wave velocity, the point load index, the Schmidt hammer rebound number and porosity were used as inputs for both meth-ods. The regression equations show that the relationship between P-wave velocity, point load index, Schmidt hammer rebound number and the porosity input sets with uniaxial compressive strength and modulus of elasticity under conditions of linear rela-tions obtained coefficients of determination of (R2) of 0.64 and 0.56, respectively. ANNs were used to improve the regression re-sults. The generalized regression and feed forward neural networks with two outputs (UCS and E) improved the coefficients of determination to more acceptable levels of 0.86 and 0.92 for UCS and to 0.77 and 0.82 for E. The results show that the proposed ANN methods could be applied as a new acceptable method for the prediction of uniaxial compressive strength and modulus of elasticity of intact rocks.
基金supported by National Natural Science Foundation of China (grants No. 41572035, 41472309, 41603041 and 41741026)the Open Funds of State Key Laboratory of Loess and Quaternary Geology (grant No. SKLLQG1620)
文摘Objective One of major challenges in paleoenvironmental reconstruction using travertine in the Huanglong area is whether one can accurately determinate the age of travertine through high-precision and high-resolution dating techniques. Previous works of 14C or ESR chronology, however, have shown that the variation of deposition ages of travertine was displayed inconsistent with each other even conflict. For instance, （1） The oldest travertine age （80 ka） located in the middle of this travertine succession is departure from sequential deposition; （2） Top or boundary ages in this sedimentary section, even with the same dating method （14C）, are three times errors, moreover, the age of the depositional sequence is not continuous. We report here the U230Th ages in lowest boundary of travertine in Dawanzhangjia Valley, Huanglong, China, to discuss the effectiveness of U-series dating for cold-water travertine and the significance of age for vicissitude of paleoenvironment.
基金financially supported by China National Major Basic Development Program "973" (2011CB403003)
文摘1 Introduction Dogai Coring is a name of lake lied in the northern Tibet.There are a series of modern salt springs and theies travertines.All of salt springs have an anomaly of potassium,implying that springs water may dissolve evaporites from deep bed formation,which includes halite
基金The research work was financially supported by the National Natural Science Foundation of China (Grant No. 49832005) the Ministry of Science and Technology of China (95-pre-39).
文摘Travertine deposited around the Niangziguan karst springs was used as a new type of paleoclimate record in this study. Five stages of climate change in northern China from 200± ka to 36± ka before the present (B. P.) were reconstructed using the 18O and 13C isotope record of the travertine. Tendency of the change was towards a more arid climate. Coupling the temporal-spatial evolution of the springs with climate change, the hydrogeological evolution could be divided into four major periods since middle Pleistocene: (1)No spring period; (2)The initial period of spring outcropping as the predominant way of discharge; (3)The culmination period of spring development; and (4)The spring discharge attenuation period. The attenuation is partly related to the decrease of recharge as a result of the dry climate after 90±kaBP.
文摘Energy consumption of block-cutting machines represents a major cost item in the processing of travertines and other natural stones. Therefore, determining the optimum sawing conditions for a particular stone is of major importance in the natural stone-processing industry. An experimental study was carried out utilizing a fully instrumented block-cutter to investigate the sawing performances of five different types of travertine blocks during cutting with a circular diamond saw. The sawing tests were performed in the down-cutting mode. Performance measurements were determined by measuring the cutting speed and energy consumption. Then, specific energy was determined. The one main cutting parameter, cutting speed, was varied in the investigation of optimum cutting performance. Furthermore, some physico-mechanical properties of file travertine blocks were determined in the laboratory. As a result, it is found that the energy consumption （specific energy） of block cutting machines is highly affected by cutting speed. It is determined that specific energy value usually decreases when cutting speed increases. When the cutting speed is higher than the determined value, the diamond saw can become stuck in the travertine block; this situation can be a problem for the block-cutting machine. As a result, the optimum cutting speed obtained for the travertine mines examined is approximately 1.5-2.0 m/min.
