In order to investigate the aerodynamic behavior of the Sutong bridge over Yangtze River during erection, a 1：50 sectional model of the bridge deck, a 1： 100 full aeroelastic model of the free standing pylon and a 1...In order to investigate the aerodynamic behavior of the Sutong bridge over Yangtze River during erection, a 1：50 sectional model of the bridge deck, a 1： 100 full aeroelastic model of the free standing pylon and a 1： 125 full aeroelastic model for the maxim cantilever configuration were built. The test results show that there was no serious vortex-induced vibration at the bridge deck, and that the free standing tower, the model scale and the turbulence intensity influenced static loading. The buffeting responses during the maximum cantilever configuration did not affect the safety of the bridge under construction.展开更多
A series of researches on mechanical behaviors of big pipe roof for shallow large-span loess tunnel were carried out based on the Wenxiang tunnel in Zhengzhou—Xi'an Special Passenger Railway. The longitudinal def...A series of researches on mechanical behaviors of big pipe roof for shallow large-span loess tunnel were carried out based on the Wenxiang tunnel in Zhengzhou—Xi'an Special Passenger Railway. The longitudinal deformations of the pipe roofs were monitored and the mechanical behaviors of the pipe roofs were analyzed at the test section. A new double-parameter elastic foundation beam model for pipe roof in shallow tunnels was put forward in Wenxiang tunnel. The measured values and the calculation results agreed well with each other,revealing the force-deformation law of big pipe roof in loess tunnel:At about 15 m in front of the excavating face,the pipe roof starts to bear the load;at about 15 m behind the excavating face,the force of the pipe roof tends to be stabilized;the longitudinal deformation of the whole pipe roofs is groove-shaped distribution,and the largest force of pipe roofs is at the excavating face. Simultaneously,the results also indicate that mechanical behaviors of pipe roof closely relate to the location of the excavation face,the footage of the tunnelling cycle and the mechanics parameters of pipe roof and rock. The conclusions can be reference for the design parameter optimization and the construction scheme selection of pipe roofs,and have been verified by the result of numerical analysis software FLAC3Dand deformation monitoring.展开更多
In this paper, stress behavior of shallow tunnels under simultaneous non-uniform surface traction and symmetric gravity loading was studied using a direct boundary element method（BEM）. The existing fullplane elastos...In this paper, stress behavior of shallow tunnels under simultaneous non-uniform surface traction and symmetric gravity loading was studied using a direct boundary element method（BEM）. The existing fullplane elastostatic fundamental solutions to displacement and stress fields were used and implemented in a developed algorithm. The cross-section of the tunnel was considered in circular, square, and horseshoe shapes and the lateral coefficient of the domain was assumed as unit quantity. Double-node procedure of the BEM was applied at the corners to improve the model including sudden traction changes. The results showed that the method used was a powerful tool for modeling underground openings under various external as well as internal loads. Eccentric loads significantly influenced the stress pattern of the surrounding tunnel. The achievements can be practically used in completing and modifying regulations for stability investigation of shallow tunnels.展开更多
Most of infrastructure projects around the world have to focus on a clear understanding of geological model which may be determined from various sources of information. The limitation in geotechnical data and budget a...Most of infrastructure projects around the world have to focus on a clear understanding of geological model which may be determined from various sources of information. The limitation in geotechnical data and budget affects the accuracy of the geological model, particularly for projects of long and deep tunnel of which accessibility to the excavation points is difficult and far reaching. Therefore, an approach adopted for interpretation plays an important role in the level of uncertainty of the derived geological model. This paper focuses on the determination of the geological models at the site of a long water diversion tunnel project in a complex geologic setting in northern Thailand from an approach to understand the relationship between regional tectonic setting and local tectonic condition so that geological structures and rock mass conditions along the tunnel alignment can be assessed for a better planning of tunnel design and construction. The paper describes tectonic settings at regional scale (Northern Thailand and Eastern Myanmar), tectonic features and geologic condition in project area, geotechnical investigation and data along tunnel alignment and predicted tunnel ground behavior.展开更多
The coverage and temperature-dependent nucleation behaviors of the Gd@C82 metallofullerenes on Cu（111） have been studied by low-temperature scanning tunneling microscopy （LT-STM） in detail. Upon molecular depositi...The coverage and temperature-dependent nucleation behaviors of the Gd@C82 metallofullerenes on Cu（111） have been studied by low-temperature scanning tunneling microscopy （LT-STM） in detail. Upon molecular deposition at low temperature, Gd@C82 molecules preferentially decorate the steps and nucleate into single layer islands with increasing coverage. Further annealing treatment leads some of the Gd@C82 molecules to assemble into bright and dim patches, which are correlated to the adsorption induced substrate reconstruction. Upon sufficient thermal activation, Gd@C82 molecules sink into the Cu（111） surface one-copper-layer-deep, forming hexagonal close-packed molecular islands with intra-molecular details observed as striped patterns. By considering the commensurability between the Gd@C82 nearest-neighbor distance and the lattice of the underlying Cu（111）, we clearly identified two kinds of in-plane molecular arrangements as （19（1/2）×19（1/2））R23.4°and （19（1/2）×19（1/2））R36.6°with respect to Cu（111）. Within the assembled Gd@C82 molecular, island molecules with dim–bright contrast are spatially distributed, which may be modulated by the preexisted species on Cu（111）.展开更多
Since 2000, the French National Radioactive Waste Management Agency （ANDRA） has been constructing an Underground Research Laboratory （URL） at Bure （east of the Paris Basin） to perform experiments in order to obt...Since 2000, the French National Radioactive Waste Management Agency （ANDRA） has been constructing an Underground Research Laboratory （URL） at Bure （east of the Paris Basin） to perform experiments in order to obtain in situ data necessary to demonstrate the feasibility of geological repository in the Callovo- Oxfordian claystone. An important experimental program is planned to characterize the response of the rock to different drift construction methods, Before 2008, at the main level of the laboratory, most of the drifts were excavated using pneumatic hammer and supported with rock bolts, sliding steel arches and fiber shotcrete. Other techniques, such as road header techniques, stiff and flexible supports, have also been used to characterize their impacts. The drift network is developed following the in situ major stresses. The parallel drifts are separated enough so as they can be considered independently when their hydromechanical （HM） behaviors are compared. Mine-by experiments have been performed to measure the HM response of the rock and the mechanical loading applied to the support system due to the digging and after excavation. Drifts exhibit extensional （mode I） and shear fractures （modes II and III） induced by excavation works. The extent of the induced fracture networks depends on the drift orientation versus the in situ stress field. This paper describes the drift convergence and deformation in the surrounding rock walls as function of time and the impact of different support methods on the rock mass behavior. An observation based method is finally applied to distinguish the instantaneous and time-dependent parts of the rock mass deformation around the drifts.展开更多
基金The National Natural Science Foundation of China(Nos.50808148 and 90815016)
文摘In order to investigate the aerodynamic behavior of the Sutong bridge over Yangtze River during erection, a 1：50 sectional model of the bridge deck, a 1： 100 full aeroelastic model of the free standing pylon and a 1： 125 full aeroelastic model for the maxim cantilever configuration were built. The test results show that there was no serious vortex-induced vibration at the bridge deck, and that the free standing tower, the model scale and the turbulence intensity influenced static loading. The buffeting responses during the maximum cantilever configuration did not affect the safety of the bridge under construction.
基金Major Science and Technology R&D Program of Ministry of Railways(No.2005K001-D(G)-2)
文摘A series of researches on mechanical behaviors of big pipe roof for shallow large-span loess tunnel were carried out based on the Wenxiang tunnel in Zhengzhou—Xi'an Special Passenger Railway. The longitudinal deformations of the pipe roofs were monitored and the mechanical behaviors of the pipe roofs were analyzed at the test section. A new double-parameter elastic foundation beam model for pipe roof in shallow tunnels was put forward in Wenxiang tunnel. The measured values and the calculation results agreed well with each other,revealing the force-deformation law of big pipe roof in loess tunnel:At about 15 m in front of the excavating face,the pipe roof starts to bear the load;at about 15 m behind the excavating face,the force of the pipe roof tends to be stabilized;the longitudinal deformation of the whole pipe roofs is groove-shaped distribution,and the largest force of pipe roofs is at the excavating face. Simultaneously,the results also indicate that mechanical behaviors of pipe roof closely relate to the location of the excavation face,the footage of the tunnelling cycle and the mechanics parameters of pipe roof and rock. The conclusions can be reference for the design parameter optimization and the construction scheme selection of pipe roofs,and have been verified by the result of numerical analysis software FLAC3Dand deformation monitoring.
文摘In this paper, stress behavior of shallow tunnels under simultaneous non-uniform surface traction and symmetric gravity loading was studied using a direct boundary element method（BEM）. The existing fullplane elastostatic fundamental solutions to displacement and stress fields were used and implemented in a developed algorithm. The cross-section of the tunnel was considered in circular, square, and horseshoe shapes and the lateral coefficient of the domain was assumed as unit quantity. Double-node procedure of the BEM was applied at the corners to improve the model including sudden traction changes. The results showed that the method used was a powerful tool for modeling underground openings under various external as well as internal loads. Eccentric loads significantly influenced the stress pattern of the surrounding tunnel. The achievements can be practically used in completing and modifying regulations for stability investigation of shallow tunnels.
文摘Most of infrastructure projects around the world have to focus on a clear understanding of geological model which may be determined from various sources of information. The limitation in geotechnical data and budget affects the accuracy of the geological model, particularly for projects of long and deep tunnel of which accessibility to the excavation points is difficult and far reaching. Therefore, an approach adopted for interpretation plays an important role in the level of uncertainty of the derived geological model. This paper focuses on the determination of the geological models at the site of a long water diversion tunnel project in a complex geologic setting in northern Thailand from an approach to understand the relationship between regional tectonic setting and local tectonic condition so that geological structures and rock mass conditions along the tunnel alignment can be assessed for a better planning of tunnel design and construction. The paper describes tectonic settings at regional scale (Northern Thailand and Eastern Myanmar), tectonic features and geologic condition in project area, geotechnical investigation and data along tunnel alignment and predicted tunnel ground behavior.
基金the National Natural Science Foundation of China(Grant No.11004219)MOST of China(Grant No.2013CBA01600)
文摘The coverage and temperature-dependent nucleation behaviors of the Gd@C82 metallofullerenes on Cu（111） have been studied by low-temperature scanning tunneling microscopy （LT-STM） in detail. Upon molecular deposition at low temperature, Gd@C82 molecules preferentially decorate the steps and nucleate into single layer islands with increasing coverage. Further annealing treatment leads some of the Gd@C82 molecules to assemble into bright and dim patches, which are correlated to the adsorption induced substrate reconstruction. Upon sufficient thermal activation, Gd@C82 molecules sink into the Cu（111） surface one-copper-layer-deep, forming hexagonal close-packed molecular islands with intra-molecular details observed as striped patterns. By considering the commensurability between the Gd@C82 nearest-neighbor distance and the lattice of the underlying Cu（111）, we clearly identified two kinds of in-plane molecular arrangements as （19（1/2）×19（1/2））R23.4°and （19（1/2）×19（1/2））R36.6°with respect to Cu（111）. Within the assembled Gd@C82 molecular, island molecules with dim–bright contrast are spatially distributed, which may be modulated by the preexisted species on Cu（111）.
文摘Since 2000, the French National Radioactive Waste Management Agency （ANDRA） has been constructing an Underground Research Laboratory （URL） at Bure （east of the Paris Basin） to perform experiments in order to obtain in situ data necessary to demonstrate the feasibility of geological repository in the Callovo- Oxfordian claystone. An important experimental program is planned to characterize the response of the rock to different drift construction methods, Before 2008, at the main level of the laboratory, most of the drifts were excavated using pneumatic hammer and supported with rock bolts, sliding steel arches and fiber shotcrete. Other techniques, such as road header techniques, stiff and flexible supports, have also been used to characterize their impacts. The drift network is developed following the in situ major stresses. The parallel drifts are separated enough so as they can be considered independently when their hydromechanical （HM） behaviors are compared. Mine-by experiments have been performed to measure the HM response of the rock and the mechanical loading applied to the support system due to the digging and after excavation. Drifts exhibit extensional （mode I） and shear fractures （modes II and III） induced by excavation works. The extent of the induced fracture networks depends on the drift orientation versus the in situ stress field. This paper describes the drift convergence and deformation in the surrounding rock walls as function of time and the impact of different support methods on the rock mass behavior. An observation based method is finally applied to distinguish the instantaneous and time-dependent parts of the rock mass deformation around the drifts.
