Guangxi Communications Planning Surveying And Designing Institute
Guangxi Communications Planning Surveying And Designing Institute
Zhou Z.,Central South University |
Zhao Y.,Central South University |
Chen Z.,Guangxi Communications Planning Surveying and Designing Institute |
Du X.,Central South University |
Wu Z.,Central South University
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2017
In order to reveal the diffusion law and consolidation effect in high pressure slurry of compaction grouting, the particle flow method was used to analyze the meso-mechanism of grouting in consideration of different grouting pressures, soil cohesion force and friction coefficient. With particle flow fish language, the grouting model was established, and the servo mechanism was used to apply different grouting pressures to simulate the grouting process. The results show that with the increase of grouting pressure, soil around the grouting point is compressed gradually, and the soil porosity becomes smaller. The soil within radius of 0.5 m around the grouting point is the most sensitive to the grouting pressure and deforms most rapidly. The additional stress of the soil around the grouting point increases with the increase of the grouting pressure. There is an optimum grouting pressure for a specific soil condition in practice. The cohesion force of soil particles has significant influence on the slurry diffusion. When the soil cohesion force is small, the radius of grouting bulbs increases with the increase of grouting pressure. When the soil cohesion force is big, grouting pressure has little effect of on the grouting bulb size. The effect of compaction grouting is undermined in this situation greatly. The friction coefficient of soil particles has little influence on the grouting performance. © 2017, Central South University Press. All right reserved.
Yu H.,Nanjing University of Aeronautics and Astronautics |
Tan Y.,Nanjing University of Aeronautics and Astronautics |
Yang L.,Guangxi Communications Planning Surveying and Designing Institute
Journal of Materials in Civil Engineering | Year: 2017
The present work investigates the microstructural evolution process of concrete under chemical attack by magnesium sulfate solution or a composite solution (sodium sulfate and magnesium chloride), salt crystallization attack through dry-wet cycles, and bending stress. The composition and microstructure are studied in detail using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of the relative dynamic elastic modulus and visual inspection analysis indicate that damage and deterioration of concrete from the composite solution are more serious than those from magnesium sulfate. Moreover, damage and deterioration of concrete under chemical attack are remarkably accelerated by salt crystallization and bending stress. According to the microstructural analysis, crack initiation elements (a new concept) are present in the concrete, which are expected to lead to crack generation and expansion in the concrete. After the corrosion of concrete under chemical attack, salt crystallization attack and bending stress for 903 days, several crack initiation elements are found in the SEM photographs of the concrete, and a grouping of microcracks appears in the concrete. These microcracks form a network by diffusion and connection. The results show that the composite solution is a more severe corrosion medium than magnesium sulfate, according to a comparison of the crack width. © 2016 American Society of Civil Engineers.
Cen C.X.,Guilin University of Electronic Technology |
Cen C.H.,Guangxi Communications Planning Surveying And Designing Institute |
Bai J.Q.,Guilin University of Electronic Technology
Applied Mechanics and Materials | Year: 2013
With the development of various infrastructure construction, the demand of sand is increasing. The supply of natural sand could not meet the requirements of engineering due to the excessive exploitation and using the Manufactured sand which instead of natural sand is one of the effective methods to resolve the shortage of natural sand. Based on the experimental study of mechanism of used sand and natural sand masonry mortar in water retention, density and consistence, this paper analyzed the difference between the masonry mortar mixed manufactured sand and the one mixed by Natural sand. The result of study can provide the reference in engineering practice which use the masonry mortar mixed manufactured sand not but mixed by Natural sand. © (2013) Trans Tech Publications, Switzerland.
Zheng G.,China Merchants Chongqing Communications Research and Design Institute Co. |
Li G.,China Merchants Chongqing Communications Research and Design Institute Co. |
Li G.,Guangxi Communications Planning Surveying and Designing Institute
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2013
Based on the three-component yield displacement model, and principal influence factors are analyzed considering the bending, shear and bar-slip deformations. New formulae with five coefficients and three coefficients are respectively proposed for the effective stiffness computation of bridge piers. The coefficients of the new formulae were calibrated with the pseudo-static test results of 75 model columns through regression analysis. The results show that the effective stiffness of bridge piers increases most consistently with axial-load ratio, longitudinal reinforcement ratio and aspect ratio, while decreases with an increase in the fydb/L√fc′. From the point of the average statistical meaning, existing formulae severely overestimate the effective stiffness of piers. Compared with the existing formulas for calculating the effective stiffness of piers, the proposed formulas agree well the test results and can provide higher accuracy and greatly reduce the degree and possibility of possible overestimation.
Li D.,Guangxi Communications Planning Surveying and Designing Institute
Modern Tunnelling Technology | Year: 2013
This paper introduces 3D geological modeling techniques for expressway tunnels, including a special data model, key factors for modeling, and modeling procedures. It also compares the advantages and disadvantages of various methods and procedures. Based on a discrete smooth interpolation algorithm, the interpolation method using geological drill hole points, key points on geological section lines and interpolated key points are presented, as well as the method used to generate the tunnel based on a polygon of arbitrary shape and space. These techniques solved the cutting down problem of interface between any tunnel and geological body. The panorama 3D geological model was set up for the Lingjiao Tunnel using information regarding the stratum, 3D tunnel, and fault.
Li G.,Guangxi Communications Planning Surveying and Designing Institute |
Tang G.,China Merchants Chongqing Communications Research and Design Institute Co. |
Zheng G.,Chongqing Jiaotong University
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2016
Based on the three-component ultimate displacement model, principal influence factors of plastic hinge length are analyzed considering the bending, shear and bar-slip deformations. The theoretical formula and empirical formula for equivalent plastic hinge length of bridge column are suggested based on the test results of 40 circular reinforced concrete bridge columns. The formulae of plastic hinge length proposed by authors and other specifications are validated by scale and full-scale reinforced concrete bridge column experiments. The results show that the equivalent plastic hinge length of bridge column increases most consistently with specimen length, section height, fydb/√(f'c) and longitudinal reinforcement ratio, while independent on the axial-load ratio and the transverse reinforcement ratio. From the point of the average statistical meaning, these expressions of plastic hinge length of existing specifications are conservative but discrete. The recommended expression in JRA specification is most conservative, and JTG/T B02-01-2008 Specification gives more conservative results compared with Caltrans and Eurocode8 specifications. The proposed theoretical plastic hinge length is approximate to that in JRA specification. The proposed empirical expression is statistically close to Caltrans and Eurocode8 with smaller variation coefficient and higher guaranteed rate. © 2016, Editorial Office of China Civil Engineering Journal. All right reserved.
Yang L.,Guangxi Communications Planning Surveying and Designing Institute |
Zeng X.-C.,Nanjing University of Aeronautics and Astronautics |
Yu H.-F.,Nanjing University of Aeronautics and Astronautics
Construction and Building Materials | Year: 2015
Abstract A new quantitative method is introduced to depict the micro-cracks in the concrete - crack density, which is closely related to the number and the size of the cracks in concrete. According to the experimental data and relative corrosion depth, the data analysis and numerical simulation are conducted by the scientific plotting and data processing software SigmaPlot 12.0 to the damage process, which can produce the three-dimensional distribution map of propagation of inner crack density of concrete. From the map we can see the formula and character on the propagation of micro-crack density of concrete in corrosive medium. In this paper, three types of concrete under the action of external stress and attack of sulfate was investigated. By analyzing the crack density, we can conclude: GHDC2 has the best stress corrosion resistance in four kinds of concrete; chloride can accelerate the chemical corrosion of magnesium and sulfate brine to concrete; tensile stress and compressive stress can obviously improve the appearance and propagation of micro-cracks. © 2015 Published by Elsevier Ltd.
Zhu J.,Guangxi Communications Planning Surveying and Designing Institute |
Li Y.,Changsha University of Science and Technology
Geotechnical Special Publication | Year: 2011
Tunnels are often located in complex geological environments and are subject to both during and after construction defects. Cracking of the tunnel lining is one of the most common and serious defects occurring in tunnels. It reduces the durability of the concrete lining and ultimately, the durability and structural performance of the whole tunnel. In this study, both the quality and cracking of the concrete lining of a railway tunnel in Hunan Province (China) was investigated using non-destructive test methods; namely the ground penetrating radar (GPR) and ultrasonic waves. Test results of these measurements including the concrete lining thickness and crack depths/width are presented in this paper. Additionally, uniaxial compressive strength testing of the concrete lining was also conducted in the laboratory and is also discussed in this paper. Based on the study findings, remedial measures were implemented to minimize further deterioration of the tunnel lining. To date, the tunnel remains structurally safe for train operations. © 2011 ASCE.
Pu C.-Z.,Central South University |
Cao P.,Central South University |
Yi Y.-L.,Guangxi Communications Planning Surveying and Designing Institute
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2012
The compression test on rock-like specimens with two prefabricated transfixion fissures made by pulling out the embedded metal inserts in the precured period was done using the servo control uniaxial loading tester. Based on the sliding crack model, the fracture failure mechanism of the fissure body was analyzed combined with the stress-strain curve and the failure form of granule on the transfixion surface of the specimen. It was shown by the sliding crack model that: the effective shear, which drove the relative sliding, was a function of the fissure inclination angle (α) and friction coefficient (f) of the fissure surface. It was found during the test that: when the fracture failure of specimens occurred, according to the differences of the fissure and rock-bridge inclination angle, the transfixion failure of micro-cracks at the tip of the signal fissure, the transfixion failure of the prefabricated fissures and the brittle failure without micro-cracks would appear in turn on specimens; and according to the differences of the stress characteristics in the rock-bridge region, when the transfixion failure of fissures occurred, three forms would be shown: tension fracture, shear fracture and tension-shear combined fracture, and the failure forms of the granule on the transfixion surface in the rock-bridge region would present zero-friction, entire-friction and partial friction, respectively.
Zhang G.,Guangxi Communications Planning Surveying and Designing Institute |
Yan L.,Changsha University of Science and Technology
Geotechnical Special Publication | Year: 2011
In recent years, Geosynthetics and piles have become the commonly applied method of embankment reinforcement, giving rise to what is typically known as Geosynthetic-reinforced pile-supported embankment. The reinforced earth platform includes one or more layers of Geosynthetics at the base of the embankment. With this method, the weight of the embankment and the surcharge are largely transferred onto the piles so that the soft soil between the piles carry less load and the embankment settlement is reduced. A numerical study was conducted to investigate the stress distributions and the transfer behavior of the Geosynethic-reinforced embankments on deep-composite columns. Five influencing factors were evaluated which included the elastic modulus of the deep-composite columns, the elastic modulus of the soft soil, the tensile stiffness of the Geosynthetics, the spacing of the columns, and the number of Geosynthetics. Numerical results suggested that the elastic modulus ratio of the deep-mixed columns to soft soil has great influence on the average stress concentration ratio of the piles to the soft soil. © 2011 ASCE.