Increase of Wave Velocity in Precast Pile along with Time and Its Analysis

Low strain dynamic testing on actual pile was conducted to investigate if the wave velocity is varied in the installed pre-cast pile.It was found that the wave velocity of the pile is raised along with time.The analysis has been carried out through with one dimension and three dimension stress wave propagation theories.Among various factors influencing the rise of wave velocity,the factor of the side soil contribution is the chief one.The soil around the pile works jointly with the pile,as if to enlarge the section size of the pile.Both the increase of wave velocity and the bearing capacity of pile are consistent.So the time effect of wave velocity can be used to study the time effect of bearing capacity of the pile and to determine the bearing capacity of piles.     

Effect of Disturbance on the Cylindrical Cavity Expansion in Saturated Soft Clay

According to the fact that the undrained shear strength decreases in the field vane test,applying the cylindrical expansion theory and assuming that the saturated soft clay satisfies Tresca yield criterion,the disturbance degree function D is given on the basis of the sensibility of saturated soft clay.Considering that the undrained shear strength is the linear function of the disturbance degree D in plastic region,the elastic-plastic solution of the cylindrical expansion has been gained.     

Research on Index of Reliability for Bearing Capacity of Rock - Socketed Single Pile in Chongqing

Based on the data from in-situ 102 rock-socketed test piles in Chongqing in recent 10 years and utilizing the limit state equation of the dimensionless random variables,the reliability analysis of the bearing capacity of rock-socketed single pile is made and the scope of the target reliability of rock-socketed piles in Chongqing is calculated with both JC method and Monte-Carlo method respectively.Furthermore,the target index of reliability is suggested.Finally,the concept of reliability coefficient(to replace the load partial factor and the resistance partial factor) is given and the bearing capacity of the single pile is determined by utilizing optimization method.Besides,the practical limit state design equation using reliability coefficient is put forward for its advantage of incarnating the simple and practical principle and being easy mastered and understood by the designers.