The formation of Danxia landscapes is too slow to be observed in our life time and the paleoclimates in which Danxia landscapes developed are significantly different from the present. Thus, this study adopted experime...The formation of Danxia landscapes is too slow to be observed in our life time and the paleoclimates in which Danxia landscapes developed are significantly different from the present. Thus, this study adopted experimental approaches to examine the lithological and paleoclimatic control on the formation of various landscape morphologies in the Mt. Danxiashan, South China. A total of 122 rock samples were collected from a range of Danxia landscape morphologies such as white spots, small and large through caves, honeycomb caves, horizontal grooves, natural bridges, stone pillars, and squama stones. Analyses of the collected samples were conducted in different kinds of experiments, including uniaxial mechanical strength testing; rock resistance against sulfuric acid erosion, freezing, and thawing; X-ray fluorescence spectrometry（XRF） analysis; inductively coupled plasma mass spectrometry（ICP-MS） analysis; and identification analysis under a polarizing microscope. The results indicated that the formation of the various Danxia landscape morphologies could result from one or more of the following processes： differential erosion due to lithological difference, chemical dissolution and recrystallization, freezing and thawing actions, acid corrosion, weathering, lateral erosion of river flows, and tectonic uplifts. Water erosion in humid monsoon climate and the alternations of intensive freezing and thawing actions in the Quaternary glacial stages and the interglacial stages could have had great influences on the formation of Danxia landscape topographies.展开更多
Pisha sandstone is a soft rock found in the southern zone of the Inner Mongolia Autonomous Region of Inner Mongolia. The presence of soft Pisha sandstone in the middle reaches of the Yellow River coincides with large ...Pisha sandstone is a soft rock found in the southern zone of the Inner Mongolia Autonomous Region of Inner Mongolia. The presence of soft Pisha sandstone in the middle reaches of the Yellow River coincides with large areas of bedrock erosion in the river’s basin, with the average total erosion modulus as high as 44 570 t/(km^2·a). Such high levels of erosion are one of the main sources of coarse mud and sands in the Yellow River. Erosion by gravitational forces such as snow glide and landslip are the main erosion types in Pisha sandstone region. The gravity erosion modulus can be as high as 25 615 t/(km^2·a), accounting for 30.6% of the total average erosion. Our paper investigates the characteristics of Pisha sandstone in relation to the development of gravity erosion mechanisms. We conducted field investigations in Pisha sandstone region for original state rock sampling. Test results from analyses of the rock properties indicate that the mineral composition, structure and microstructure characteristics of Pisha sandstone determine its varying capacity to resist weathering. Degrees of weathering in slightly different lithological layers of Pisha sandstone lead to different erosion rates. In this way, erosion forces combined with the varying lithological strata in the rock aggravate gravitational erosion in Pisha sandstone.展开更多
In many engineering applications such as mining,geotechnical and petroleum industries,drilling operation is widely used.The drilling operation produces sound by-product,which could be helpful for preliminary estimatio...In many engineering applications such as mining,geotechnical and petroleum industries,drilling operation is widely used.The drilling operation produces sound by-product,which could be helpful for preliminary estimation of the rock properties.Nevertheless,determination of rock properties is very difficult by the conventional methods in terms of high accuracy,and thus it is expensive and timeconsuming.In this context,a new technique was developed based on the estimation of rock properties using dominant frequencies from sound pressure level generated during diamond core drilling operations.First,sound pressure level was recorded and sound signals of these sound frequencies were analyzed using fast Fourier transform (FFT).Rock drilling experiments were performed on five different types of rock samples using computer numerical control (CNC) drilling machine BMV 45 T20.Using simple linear regression analysis,mathematical equations were developed for various rock properties,i.e.uniaxial compressive strength,Brazilian tensile strength,density,and dominant frequencies of sound pressure level.The developed models can be utilized at early stage of design to predict rock properties.展开更多
Wellbore drilling operations frequently entail the combination of a wide range of variables. This is underpinned by the numerous factors that must be considered in order to ensure safety and productivity. The heteroge...Wellbore drilling operations frequently entail the combination of a wide range of variables. This is underpinned by the numerous factors that must be considered in order to ensure safety and productivity. The heterogeneity and sometimes unpredictable behaviour of underground systems increases the sensitivity of drilling activities. Quite often the operating parameters are set to certify effective and efficient working processes. However, failings in the management of drilling and operating conditions sometimes result in catastrophes such as well collapse or fluid loss. This study investigates the hypothesis that optimising drilling parameters, for instance mud pressure, is crucial if the margin of safe operating conditions is to be properly defined. This was conducted via two main stages： first a deterministic analysis--where the operating conditions are predicted by conventional modelling procedures--and then a probabilistic analysis via stochastic simulations--where a window of optimised operation conditions can be obtained. The outcome of additional stochastic analyses can be used to improve results derived from deterministic models. The incorporation of stochastic techniques in the evaluation of wellbore instability indicates that margins of the safe mud weight window are adjustable and can be extended considerably beyond the limits of deterministic predictions. The safe mud window is influenced and hence can also be amended based on the degree of uncertainty and the permissible level of confidence. The refinement of results from deterministic analyses by additional stochastic simulations is vital if a more accurate and reliable representation of safe in situ and operating conditions is to be obtained during wellbore operations.展开更多
Combining with empirical method, laboratory test and numerical simulation, a comprehensive system was presented to determine the mechanical parameters of jointed rock masses. The system has the following four function...Combining with empirical method, laboratory test and numerical simulation, a comprehensive system was presented to determine the mechanical parameters of jointed rock masses. The system has the following four functions: (1) Based on the field investigation of joints, the system can consider rock mass structures, by using network simulation technology. (2) Rock samples are conducted by numerical simulation with the input engineering mechanical parameters of rocks and joints obtained from laboratory tests. (3) The whole stress-strain curve of jointed rock masses under certain normal stress can be plotted from numerical simulation, and then the shear strength parameters of jointed rock masses can be obtained from the whole stress-strain curves under different normal stresses. (4) The statistical values of mechanical parameters of jointed rock masses can be determined according to numerical simulation. Based on the statistical values, combining with engineering experiences and geological investigations, the comprehensive mechanical parameters of jointed rock masses can be achieved finally. Several cases are presented to prove the engineering feasibility and suitability of this system.展开更多
基金National Natural Science Foundation of China, No.41371204 No.41171163+6 种基金 No.41401216 National Science and Technology Basic Special Key Project, No.2013FY 11 1900 Foundation of State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, No.SKLLQG1206 No.SKLLQG1422 National Basic Science Personnel Training Project, No.J1103408 Foundation of Modern Analysis Center, Nanjing University, No.0422171010 Priority Academic Program Development of Jiangsu Higher Education Institutions, No.PAPD,Acknowledgements We appreciate the laboratory and field assistance of KONG Qingyou, LIU Di, YANG Li, WANG Xiaocui, FU Jingcheng, LIANG Guomin, MAO Xiaodong, FAN Dengfeng, LUO Jiehong, WU Huaan, TAN Ming, DAI Huibao, and XIE Zhangzhen.
文摘The formation of Danxia landscapes is too slow to be observed in our life time and the paleoclimates in which Danxia landscapes developed are significantly different from the present. Thus, this study adopted experimental approaches to examine the lithological and paleoclimatic control on the formation of various landscape morphologies in the Mt. Danxiashan, South China. A total of 122 rock samples were collected from a range of Danxia landscape morphologies such as white spots, small and large through caves, honeycomb caves, horizontal grooves, natural bridges, stone pillars, and squama stones. Analyses of the collected samples were conducted in different kinds of experiments, including uniaxial mechanical strength testing; rock resistance against sulfuric acid erosion, freezing, and thawing; X-ray fluorescence spectrometry（XRF） analysis; inductively coupled plasma mass spectrometry（ICP-MS） analysis; and identification analysis under a polarizing microscope. The results indicated that the formation of the various Danxia landscape morphologies could result from one or more of the following processes： differential erosion due to lithological difference, chemical dissolution and recrystallization, freezing and thawing actions, acid corrosion, weathering, lateral erosion of river flows, and tectonic uplifts. Water erosion in humid monsoon climate and the alternations of intensive freezing and thawing actions in the Quaternary glacial stages and the interglacial stages could have had great influences on the formation of Danxia landscape topographies.
基金supported by the public program of Ministry of Science and Technology of China (Grant No 2005DIB3J068)
文摘Pisha sandstone is a soft rock found in the southern zone of the Inner Mongolia Autonomous Region of Inner Mongolia. The presence of soft Pisha sandstone in the middle reaches of the Yellow River coincides with large areas of bedrock erosion in the river’s basin, with the average total erosion modulus as high as 44 570 t/(km^2·a). Such high levels of erosion are one of the main sources of coarse mud and sands in the Yellow River. Erosion by gravitational forces such as snow glide and landslip are the main erosion types in Pisha sandstone region. The gravity erosion modulus can be as high as 25 615 t/(km^2·a), accounting for 30.6% of the total average erosion. Our paper investigates the characteristics of Pisha sandstone in relation to the development of gravity erosion mechanisms. We conducted field investigations in Pisha sandstone region for original state rock sampling. Test results from analyses of the rock properties indicate that the mineral composition, structure and microstructure characteristics of Pisha sandstone determine its varying capacity to resist weathering. Degrees of weathering in slightly different lithological layers of Pisha sandstone lead to different erosion rates. In this way, erosion forces combined with the varying lithological strata in the rock aggravate gravitational erosion in Pisha sandstone.
文摘In many engineering applications such as mining,geotechnical and petroleum industries,drilling operation is widely used.The drilling operation produces sound by-product,which could be helpful for preliminary estimation of the rock properties.Nevertheless,determination of rock properties is very difficult by the conventional methods in terms of high accuracy,and thus it is expensive and timeconsuming.In this context,a new technique was developed based on the estimation of rock properties using dominant frequencies from sound pressure level generated during diamond core drilling operations.First,sound pressure level was recorded and sound signals of these sound frequencies were analyzed using fast Fourier transform (FFT).Rock drilling experiments were performed on five different types of rock samples using computer numerical control (CNC) drilling machine BMV 45 T20.Using simple linear regression analysis,mathematical equations were developed for various rock properties,i.e.uniaxial compressive strength,Brazilian tensile strength,density,and dominant frequencies of sound pressure level.The developed models can be utilized at early stage of design to predict rock properties.
文摘Wellbore drilling operations frequently entail the combination of a wide range of variables. This is underpinned by the numerous factors that must be considered in order to ensure safety and productivity. The heterogeneity and sometimes unpredictable behaviour of underground systems increases the sensitivity of drilling activities. Quite often the operating parameters are set to certify effective and efficient working processes. However, failings in the management of drilling and operating conditions sometimes result in catastrophes such as well collapse or fluid loss. This study investigates the hypothesis that optimising drilling parameters, for instance mud pressure, is crucial if the margin of safe operating conditions is to be properly defined. This was conducted via two main stages： first a deterministic analysis--where the operating conditions are predicted by conventional modelling procedures--and then a probabilistic analysis via stochastic simulations--where a window of optimised operation conditions can be obtained. The outcome of additional stochastic analyses can be used to improve results derived from deterministic models. The incorporation of stochastic techniques in the evaluation of wellbore instability indicates that margins of the safe mud weight window are adjustable and can be extended considerably beyond the limits of deterministic predictions. The safe mud window is influenced and hence can also be amended based on the degree of uncertainty and the permissible level of confidence. The refinement of results from deterministic analyses by additional stochastic simulations is vital if a more accurate and reliable representation of safe in situ and operating conditions is to be obtained during wellbore operations.
基金Supported by the National Basic Research Program of China (973 Program) (2011CB013502)the National Natural Science Foundation of China (51179210)
文摘Combining with empirical method, laboratory test and numerical simulation, a comprehensive system was presented to determine the mechanical parameters of jointed rock masses. The system has the following four functions: (1) Based on the field investigation of joints, the system can consider rock mass structures, by using network simulation technology. (2) Rock samples are conducted by numerical simulation with the input engineering mechanical parameters of rocks and joints obtained from laboratory tests. (3) The whole stress-strain curve of jointed rock masses under certain normal stress can be plotted from numerical simulation, and then the shear strength parameters of jointed rock masses can be obtained from the whole stress-strain curves under different normal stresses. (4) The statistical values of mechanical parameters of jointed rock masses can be determined according to numerical simulation. Based on the statistical values, combining with engineering experiences and geological investigations, the comprehensive mechanical parameters of jointed rock masses can be achieved finally. Several cases are presented to prove the engineering feasibility and suitability of this system.
