Briefly introduced the simple shear apparatus under high stress that was developed from RMT. A series simple shear tests under high stress show that the relationcurve between shear stress and tangential displacement u...Briefly introduced the simple shear apparatus under high stress that was developed from RMT. A series simple shear tests under high stress show that the relationcurve between shear stress and tangential displacement under high normal stress is different from the hyperbolic curve in direct shear tests, and the complete deformation process of interface under high stress can be described as nonlinear elastic-perfect plastic(NEPP). According to some characteristics of the fitting curve, the deficiency of theNEPP was pointed out. The mathematic 'half value index' was used to illustrate thatWeibull distribution with three parameters (WNEPP) can overcome the mathematical deficiencies of the NEPP. The advantage of the WNEPP is that the fitting curve of WNEPPmore accurately coincided with the testing data was testified by further comparison.展开更多
Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting at more than 550 construction sites, an empirical formulation is proposed...Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting at more than 550 construction sites, an empirical formulation is proposed for the rapid determination of allowable bearing pressure of shallow foundations in soils and rocks. The proposed expression corroborates consistently with the results of the classical theory and is proven to be rapid, and reliable. Plate load tests have been also carried out at three different sites, in order to further confirm the validity of the proposed method. It consists of only two soil parameters, namely, the in situ measured shear wave velocity and the unit weight. The unit weight may be also determined with sufficient accuracy, by means of other empirical expressions proposed, using P or S -- wave velocities. It is indicated that once the shear and P-wave velocities are measured in situ by an appropriate geophysical survey, the allowable bearing pressure as well as the coefficient of subgrade reaction and many other elasticity parameters may be determined rapidly and reliably.展开更多
The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this pap...The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.展开更多
In the present research,the measurement fluctuations of mechanical properties in nanowires (NWs) are investigated by using the molecular dynamics simulation.The large numbers of simulations are performed to study the ...In the present research,the measurement fluctuations of mechanical properties in nanowires (NWs) are investigated by using the molecular dynamics simulation.The large numbers of simulations are performed to study the yield behaviors of the NWs.The results have shown that the yield behavior of the smaller diameter NW is more sensitive to the presence of vacancies,and the dispersion of the measured mechanical properties for the small scale NW is larger than that for the large scale NW.Present results have also shown that vacancies escape from the bulk to the free surfaces as a result of high stress applied at the small scale systems similar to the dislocation starvation phenomenon observed in the compression test of nano-pillars,and dislocation nucleation induced by surface defect occurs after the vacancy reaches free surface leading to lower yield strength.Moreover,the strong surface vacancy interactions at the nanoscale level are also investigated.展开更多
基金Supported by the Excellent Youth Foundation of Henan Scientific Committee(084100510004)the Natural Science Foundation of Henan Prov ince(061l010600)
文摘Briefly introduced the simple shear apparatus under high stress that was developed from RMT. A series simple shear tests under high stress show that the relationcurve between shear stress and tangential displacement under high normal stress is different from the hyperbolic curve in direct shear tests, and the complete deformation process of interface under high stress can be described as nonlinear elastic-perfect plastic(NEPP). According to some characteristics of the fitting curve, the deficiency of theNEPP was pointed out. The mathematic 'half value index' was used to illustrate thatWeibull distribution with three parameters (WNEPP) can overcome the mathematical deficiencies of the NEPP. The advantage of the WNEPP is that the fitting curve of WNEPPmore accurately coincided with the testing data was testified by further comparison.
文摘Based on a variety of case histories of site investigations, including extensive bore hole data, laboratory testing and geophysical prospecting at more than 550 construction sites, an empirical formulation is proposed for the rapid determination of allowable bearing pressure of shallow foundations in soils and rocks. The proposed expression corroborates consistently with the results of the classical theory and is proven to be rapid, and reliable. Plate load tests have been also carried out at three different sites, in order to further confirm the validity of the proposed method. It consists of only two soil parameters, namely, the in situ measured shear wave velocity and the unit weight. The unit weight may be also determined with sufficient accuracy, by means of other empirical expressions proposed, using P or S -- wave velocities. It is indicated that once the shear and P-wave velocities are measured in situ by an appropriate geophysical survey, the allowable bearing pressure as well as the coefficient of subgrade reaction and many other elasticity parameters may be determined rapidly and reliably.
基金the National Natural Science Foundation of China (Grant No. 19972068).
文摘The swell-shrinking mineral of saturated and unsaturated expansive soil has important effect on engineering mechanical behavior. Based on the swelling-shrinkage change regularity of montmorillonite crystal in this paper, the actions between various interlayers of montmorillonite crystal are generally summarized as two kinds of action potentials-shrinkage potential and swelling potential. Moreover, through the experimental research and analysis, the expression formula for variations of the swelling potential and shrinkage potential with interlayer distance is presented, and the regularity of matric suction variations with interlayer distance is also obtained for unsaturated expansive soil. It may provide a new theoretical basis and research path for further research on the swelling-shrinkage mechanism of expansive soil and matric suction potential of unsaturated soil.
基金supported by the National Natural Science Foundation of China (Grants Nos. 50904071,11021262,10932011 and 91116003)the Fundamental Research Funds for the Central Universities (Grant No.2010QZ01)the National Basic Research Program of China (Grant No.2012CB937500)
文摘In the present research,the measurement fluctuations of mechanical properties in nanowires (NWs) are investigated by using the molecular dynamics simulation.The large numbers of simulations are performed to study the yield behaviors of the NWs.The results have shown that the yield behavior of the smaller diameter NW is more sensitive to the presence of vacancies,and the dispersion of the measured mechanical properties for the small scale NW is larger than that for the large scale NW.Present results have also shown that vacancies escape from the bulk to the free surfaces as a result of high stress applied at the small scale systems similar to the dislocation starvation phenomenon observed in the compression test of nano-pillars,and dislocation nucleation induced by surface defect occurs after the vacancy reaches free surface leading to lower yield strength.Moreover,the strong surface vacancy interactions at the nanoscale level are also investigated.
