1.0.1 This specification is prepared for unifying the dynamic testing method and technical requirements of the piles in port engineering and controlling effectively the engineering testing quality.
1.0.2 This specification is applicable to dynamic testing of high strain of concrete precast pile, bored concrete pile, steel pile and composite pile of port engineering and dynamic testing of low strain of concrete precast pile and bored concrete pile. The dynamic testing of piles in navigation buildings and shipbuilding and repair hydraulic structures may refer to it.
1.0.3 The pile dynamic testing range shall meet the relevant requirements of the current professional standard "Code for Pile Foundation of Harbour Engineering" (JTJ 254).
1.0.4 Dynamic testing of piles in port engineering shall not only meet the requirements of this specification and the relevant requirements of the current national standards.
2 Symbols
2.0.1 A——Pile body section area (m2).
2.0.2 C——Stress wave speed of pile body (m/s).
2.0.3 Cm——Mean wave speed of stress wave of multiple qualified measured piles in the same field (m/s).
2.0.4 E——Elasticity modulus of pile material (MPa).
2.0.5 En——Energy transferred actually by pile hammer to the pile (KJ).
2.0.6 △f——Characteristic frequency of an integrate pile (Hz).
2.0.7 △fx——Characteristic frequency of a defect (Hz).
2.0.8 F——Hammering force measured at testing point sometime (kN).
2.0.9 Fd——Amplitude of downgoing wave at testing point sometime (kN).
2.0.10 Fmax——Maximum hammering force measured by force sensor (kN).
2.0.11 F(t1), F(t2)——Hammering force measured at testing point at t1 and t2 (kN).
2.0.12 F(tx)——Measured force at testing point at the time corresponding to the defect reflection peak (kN).
2.0.13 F(ty)——Hammering force measured at testing point at ty (kN).
2.0.14 Fu——Amplitude of upcoming wave at testing point sometime (kN).
2.0.15 g——Gravity acceleration (m/s2).
2.0.16 Jc——CASE method damping coefficient.
2.0.17 l——Distance of sensors and pile top (m).
2.0.18 L——Pile length below testing point (m).
2.0.19 △R——Estimated value of soil resistance above defect position (kN).
2.0.20 Rc——Ultimate bearing capacity of a single pile determined by CASE method (kN).
2.0.21 t——Time taken the stress wave reflected to testing point under the action of hammering force (ms).
2.0.22 t1, t2——Time corresponding to the first peak and second peak of the speed (ms).
2.0.23 tr——Arrival time of reflected wave at bottom of the pile (ms).
2.0.24 tx——Time corresponding to the reflection peak of the defect (m).
2.0.25 t’x——Arrival time of reflected wave at the low strain defect position (ms).
2.0.26 T——Ending time of sampling (ms).
2.0.27 V——Speed measured at testing point some time (m/s).
2.0.28 V(t1), V(t2)——Speed measured at testing point at t1 and t2 (m/s).
2.0.29 V(tx)——Speed at testing point at the time corresponding to the defect reflection peak (m/s).
2.0.30 V(ty)——Speed measured at testing point at ty (m/s).
2.0.31 X——Distance of calculation point and testing point (m).
2.0.32 Z——Mechanical impedance of pile body section (kN?s/m).
2.0.33 β——Pile body integrity coefficient.
2.0.34 γ——Pile material unit weight (kN/m3).
2.0.35 σp——Hammering compressive stress of maximum pile body (kPa).
2.0.36 σt——Maximum hammering tensile stress of pile body (kPa).
3 Dynamic Testing of High Strain
3.1 General Requirements
3.1.1 For dynamic testing of high strain, analyze force and acceleration of the piles under the action of impact force, determine the axial bearing capacity of pile, assess pile body integrity and analyze resistance distribution of soil and performance index of pile hammer as well as the pile body stress and instantaneous settling characteristic during piling. Where the static load test is done, the axial bearing capacity result of dynamic testing of high strain shall be compared with the static load test results.
3.1.2 Dynamic testing results of high strain may provide a basis for the works below:
(1) Check rationality of pile design parameter;
(2) Select pile sinking equipment and process;
(3) Dynamic testing assessment of piles construction quality.
3.1.3 The number of the testing pile shall be determined according to geologic condition and pile type, adopting suitably 2%~5% of the total pile number and not less than five. Under the conditions that the geologic condition is complex, pile type is relatively multiple or other special circumstances, the testing number may be appropriately added.
3.1.4 Where the axial ultimate bearing capacity testing is carried out, the interval time from testing pile sinking to testing shall not be less than 14 days for cohesive soil, three days for sandy soil and 28 days for flashing pile sinking; bored concrete pile shall not only meet the time requirements above but its concrete strength grade shall also reach the design requirements.
3.1.5 Where dynamic testing of high strain is adopted, the information below shall be provided:
(1) Relevant engineering geology, topography and hydrological data;
(2) Pile foundation construction drawing;
(3) Pile construction record;
(4) Concrete strength test report of testing pile;
(5) Elevation before and after treatment of pile top of the testing pile
3.1.6 Dynamic testing result of high strain shall form testing report which shall meet the relevant requirements of Appendix A.
