Piling construction management method
In a piling construction management method a support strength of a hole bottom is measured with a penetration testing device before erecting a piling in a piling hole. The piling is erected in the piling hole when the measurement is at least a prescribed value. The penetration testing device has a knocking block with an integrated penetration shaft and the block is struck by a drive hammer in free-fall. The penetration testing device determines the support strength from the number of impacts required for the penetration shaft to penetrate to a prescribed depth from the hole bottom.
1. A piling construction management method, comprising:
providing a penetration testing device including a knocking block integrated with a penetration shaft projecting downward, a drive hammer that strikes the knocking block in free-fall, and a lifting mechanism that lifts the drive hammer after falling and releases the drive hammer at a prescribed height;
wherein the penetration testing device is configured such that a cylindrical hammer casing incorporating the lifting mechanism and the drive hammer is held movably up and down inside a vertical cylindrical outer casing, the knocking block is fixed to a lower end of the hammer casing, and the penetration shaft penetrates through a lower end side of the outer casing and projects downward to an outside of the outer casing;
after forming a piling hole with a set depth in the ground and before erecting a piling in the piling hole, disposing the penetration shaft of the penetration testing device inside the piling hole such that the penetration shaft reaches a hole bottom, and determining a support strength of the hole bottom based on the required number of impacts by the drive hammer for the penetration shaft to penetrate to a prescribed depth from the hole bottom;
when the support strength is equal to or more than a prescribed value, erecting a piling in the piling hole; and
when the support strength is less than the prescribed value, digging the piling hole deeper to form a deeper hole bottom and determining a support strength of the deeper hole bottom based on the required number of impacts by the drive hammer for the penetration shaft to penetrate to a prescribed depth from the deeper hole bottom until the support strength of the deeper hole bottom reaches the prescribed value or more, and erecting a piling in the piling hole with a length corresponding to a depth of the deeper piling hole.
2. The piling construction management method according to claim 1 , wherein the penetration testing device incorporates an encoder that measures a sinkage amount of the hammer casing.
3. The piling construction management method according to claim 1 , further comprising suspending the penetration testing device by a wire of a crane and letting the penetration device into and out of the piling hole.
4. The piling construction management method according to claim 1 , further comprising removing a digging tip member after digging the piling hole and connecting the penetration testing device in place of the digging tip member, and letting the penetration testing device into and out of the piling hole.
5. The piling construction management method according to claim 1 , further comprising completing the determination of the support strength by activating the penetration testing device after the piling hole has been dug and in a state where a digging tip member is inserted in the piling hole.
6. The piling construction management method according to claim 1 , wherein the piling is a precast piling, and when the method requires erecting the piling in the piling hole that has been dug deeper, the erecting the piling comprises providing a piling main body with a length corresponding to the length of the piling hole that was formed first and connecting the piling main body to a shorter piling member with a length corresponding to the length of the increase in depth caused by digging the piling hole deeper.
7. The piling construction management method according to claim 6 , wherein the piling main body is a concrete piling, and the shorter piling member is a steel pipe piling connected to a lower end of the concrete piling.
8. The piling construction management method according to claim 1 , wherein the piling is a cast-in-place piling with a reinforced frame, and when the method requires erecting the piling in the piling hole that has been dug deeper, the erecting the piling comprises providing a reinforced frame main body with a length corresponding to the length of the piling hole that was formed first and connecting the reinforced frame main body to a reinforced frame extension portion with a length corresponding to the length of the increase in depth caused by digging the piling hole deeper, inserting the reinforced frame main body and reinforced frame extension portion into the piling hole, and placing fresh concrete in the piling hole to form the cast-in-place piling.