Several dynamic pile testing methods including the wave equation method, CASE method and CAPWAP method are introduced and discussed in this paper. In particular, the wave equation method is given in detail. The various types of dynamic pile driving analyzer are also described along with the acceleration and force measuring system. Finally , the errors of dynamic pile testing are described at the end of the text.

Based on the fact that the bearing capacity of pile depends of the condition of pile body, mechanical parameters of the media around it, and loading period, the mechanism of dynamic and static bearing capacity for the single-pile is studied. Considering loading rate and difference between dynamic and static mechanical strengths of rock and soil media, a dynamic measurement is proposed to determine critical bearing capacity of frictional piles, which has been proved to be simple and effective with engineering applications and comparison between dynamic and static tests.

A method named CASE method is presented for determining the statically axial bearing capacity of piles from dynamic measurements of force and acceleration performed under the impact of a large hammer. The basic equation for calculating resistance against pile penetration is derived. The examples of field measurements are given. In order to use CASE method effectively, it is necessary to determine “damping ”constant by comparison the pile bearing capacity from static method with that from CASE method, or by changing hammer weight or dropping height to cause the Vb to close on zero and to obtain the static bearing capacity of pile.

This paper describes theoretical basis, test technique , data interpretation for pile quality inspection. The propagation and attenuation law of weak stress waves in concrete piles, relationship between concrete strength and elastic wave velocity are discussed. A criterion of inspecting pile quality is proposed. The study mentioned in this paper has practical value and theoretical significance for field inspection test of pile quality.

In dynamic nondestructive inspection for pile quality, it is a key problem to determine exact location and degree of various defects according to wave analysis. In this paper, the influence of various defects on wave propagation is studied by model test of piles, and some related engineering cases are discussed.

This paper presents briefly the essential principle and measurement process of hydro-electric effect method for NDI of piles. In the past three years, more than three hundred piles from twenty project sites inspected with method. Coring piles and comparing dynamic with static tests have proved that hydro-electric effect method is available for engineering with easy operation, quick inspection, and low costs.

This paper discusses the difference between reflections of waves in frictional pile and end-bearing pile, based on the solutions of wave equations. The influences of various defects on wave are analyzed. These make theoretical basis for wave analysis of nondestructive inspection of piles.

In engineering treatment of soft and weak ground and high rise building foundations, grouting fiction piles are increasingly getting popular. This paper makes theoretical analyses to the bearing mechanism and the load transmitting behavior of these piles in the light of construction cases and in-situ practice. Determination of load transmitting behavior field tests is considered to be more close to the real case than from other methods, although there are some remaining problems from the alteration of modulus of elasticity and pile diameters.

Considering the specific conditions of deep soft ground in Wuhan, the deep cement mixing method was developed from 1987， in order to reinforce the soft ground. Since then, variety of testing studies both in lab, and in field have been made. From September to October in 1987, this method was first used to reinforce soft ground satisfied completely design requirement with allowable bearing capacity of 16 t/m2 .

This paper presents a new instrument, Sliding-Micrometer-ISETH, and its application to determination of negative friction of piles. This instrument is now used to determine negative friction and horizontal displacement of steel pipe piles for a huge power station in East of China. Eight month’s measurements demonstrate that this instrument is specially suitable for long-term measurement of variety of geotechnical engineering. In the case of stack load with a high of 4.6m, the measured maximum axial load is about 800 KN with the rising rate of 30 KN per month, whose critical value will be lower than that calculated according to effective stresses and approximate to that, if additional pore pressure is considered. The bending stress is higher than allowable stress, and the horizontal displacement is over 600 mm in a pile located at boundary of stack area. A comparison analysis is made for measured results with the data of ground settlement, horizontal displacement and pore pressure.