Dynamic loading system, dynamic loading method and dynamic loading test method for piles

A dynamic loading method for a pile, said dynamic loading method comprising:

• feeding an electric current into an exciting coil of a magnetostrictive vibrator which is connected to the head of the pile;
• and
• transmitting a strain occurring in the magnetostrictive vibrator due to a magnetic field to the pile in the form of vibrations to thereby vibrate the pile,
• wherein the magnetostrictive vibrator supports a weight of a specific mass in such a manner that the resonant frequency of the magnetostrictive vibrator which is determined by the mass of the weight and the stiffness of the magnetostrictive vibrator becomes generally equal to the resonant frequency of the pile, and the pile is vibrated at its resonant frequency or at a frequency close to its resonant frequency.

A dynamic loading test method for a pile, said dynamic loading test method comprising:

• feeding an electric current into an exciting coil of a magnetostrictive vibrator which is connected to the head of the pile;
• vibrating the pile by transmitting a strain occurring in the magnetostrictive vibrator due to a magnetic field to the pile in the form of vibrations;
• detecting vibrations produced in the ground around the pile, and
• estimating the bearing capacity of the piles
• wherein the magnetostrictive vibrator sun pots a weight of a specific mass in such a manner that the resonant frequency of the magnetostrictive vibrator which is determined by the mass of the weight and the stiffness of the magnetostrictive vibrator becomes generally equal to the resonant frequency of the pile, and the pile is vibrated at its resonant frequency or at a frequency close to its resonant frequency.

A dynamic loading test method for a pile, said dynamic loading test method comprising:

• feeding an electric current into an exciting coil of a magnetostrictive vibrator which is connected to the head of the pile;
• vibrating the pile by transmitting a strain occurring in the magnetostrictive vibrator due to a magnetic field to the pile in the form of vibrations;
• detecting vibrations produced in the ground around the pile;
• and
• estimating the bearing capacity of the pile,
• wherein the pile is vibrated by feeding an electric current into the exciting coil of the magnetostrictive vibrator, the electric current fed into the exciting coil is controlled such that the amplitude of the vibrations produced in the ground around the pile matches a preset target value, and a maximum stationary peripheral surface friction force of the pile is calculated from the value of the controlled electric current.

A dynamic loading test method for a pile, said dynamic loading test method comprising:

• feeding an electric current whose frequency varies with time into an exciting coil of a magnetostrictive vibrator which is connected to the head of the pile;
• vibrating the pile by transmitting a strain occurring in the magnetostrictive vibrator due to a magnetic field to the pile in the form of vibrations;
• detecting vibrations produced in the pile itself and in the ground around the pile by respective vibration sensors, and
• estimating the bearing capacity of the pile by calculating a transfer function from sensing signals of the respective vibration sensors.

A dynamic loading test method for a pile, said dynamic loading test method comprising:

• a first step of determining the bearing capacity of a reference pile driven into the ground in the vicinity of the pile by a stationary loading test method;
• a second step of feeding an electric current into an exciting coil of a magnetostrictive vibrator which is connected to the head of the reference pile, vibrating the reference pile by transmitting a strain occurring in the magnetostrictive vibrator due to a magnetic field to the reference pile in the form of vibrations and detecting vibrations produced in the ground around the reference pile;
• a third step of memorizing the bearing capacity of the reference pile obtained in said first step and a vibration sensing signal obtained in said second step together with information on their mutual relationship;
• a fourth step of vibrating the pile in the same way as said second step and detecting vibrations produced in the ground;
• and
• a fifth step of estimating the bearing capacity of the pile based on a vibration sensing signal obtained in said fourth step with reference to information memorized in said third step.