Numerical Assessment of Factors Affecting Waveform Based on Low Strain Testing of Piles
In this paper dynamic testing of piles using the low strain method is performed by means of numerical analyses based on solid finite element model. To this end, velocity-time curves are presented investigating the influence of various parameters such as mesh density, impulse width, receiving point, and soil modulus on the waveform characteristics. Then, find regularity of waveform affected by different parameters to provide reference of the real project detection.
Influence Factor Analysis of Foundation Model in Shaking Table Test Considering Soil-structure Dynamic Interaction
The general principle of large scale shaking table test of soil-structure dynamic interaction was investigated.Taking the amplification coefficients of peak acceleration and its corresponding Fourier amplitude spectrum as main factors,the measured results of existing typical shaking table tests were analyzed and the vibration behaviors of foundation model were compared in terms of boundary effect,height of foundation model,moisture content of soil and numbers of input seismic waves.The results show that the main factors affecting vibration behavior of foundation model are stiffness of soil box,self-vibration behavior of soil,foundation height,moisture content of soil and numbers of input seismic waves.At the same time,the corresponding control principles are proposed.These conclusions will be very helpful for the future test design of foundation model.
RATIONAL WAVE EQUATION MODEL FOR PILE-DRIVING ANALYSIS
A one-dimensional wave equation model for pile-driving analysis is presented. In this model, the pile is represented by discrete elements, while the soil is represented by a series of springs and dashpots, the coefficients of which are derived using elasto-dynamic theory. The soil model incorporates the loss of wave energy to the soil through radiation or geometric damping. In addition, the effect of the increase in soil resistance to failure when subjected to rapid loading is taken into account. The capability of the proposed model is demonstrated by comparison with field data of two instrumented piles. The analyses include predictions of set, and driving stresses at various levels of the piles. Comparisons are made with the sets and driving stresses predicted by the Smith (1960) model. From the analyses by the proposed model and load test results, estimations of soil setup for the two piles are also presented.