Comparison of Jacked and Driven H-pile

Comparison of Jacked and Driven H-pile

Type	Jacked Pile ( ArchSD’s PS(1) and VLA (2011)(2) )	Driven H-Pile (COP of Foundation(3) and BD’s EM 2.1.13(4) )
1. Design requirement
Working load (WL = 0.33Ys): i) 305x305x180kg/m ii) 305x305x223kg/m	For grade 55C 2950kN 3450kN	For grade 55C 2950kN 3450kN
Pile group reduction for group of 5 piles for spacing 3 times circumscribed rectangles of H-piles	0.85	0.85
Founding of pile	SPT N-value may less than 200	i) SPT N-value ³ 210 for 305´305´223 kg/m H-piles ii) SPT N-value ³ 180 for other H-piles (BD EM
Settlement analysis	More than 10 piles	No specify
2. Installation
Maximum jack force	(i) Not exceed 90% of total weight of the pile-jacking machine; and (ii) 80% of yield stress of H-pile	N/A
Calibration of hydraulic jack	(i) Calibrated by HOKLAS by calibrated load cell; (ii) Re-calibration at a force of 2.2.WL shall be carried out after jacking every 30 piles or repair.	N/A
Monitoring of jacking force	e.g. Pile Driving Monitor (PDM) developed by Inopiles International Pte Ltd.	N/A
Prevention of pile buckling	Gaps between the H-pile and pile hole shall be kept filled up with sand	N/A
Storage of spliced piles	To avoid idling time, several pieces of piles will be welded and stored into bored hollow shaft vertically	N/A
3. Termination procedures and criteria
Pre-creeping by pre-loading process	(i) Before termination of pile, at least 2.3WL for suitable period determined by contractor (ii) At 10% of piles (min. 5 piles) to be carried out by pre-loading test: 2.2WL until the settlement rate is less than 5mm per 15 minutes	N/A
4. Verification
Trial pile	Subject to static loading test (6.11 of PS)	Depend on actual site condition. e.g. for short pile (BD EM 2.1.4) not less than 2 testing pile which rest on bedrock (5.4.11 (4) of COP)
Verification test	The Contractor shall demonstrate with PDA analysis that driving stresses would not exceed 0.9 fy. (clause 5.18(iv) of GS)	The integrity and capacity of at least 10% of the working piles should be verified by PDA tests.
No of piles for loading test	1% minimum one pile or more (clause 5.28(ii) to (iv) of GS)	1% & at least 1 no of piles (BD EM2.1.6 & 2.1.11)
Loading test (where P = 2WL)	1st cycle: 0->0.25P->0.5P-> 0.25P->0 2nd cycle: 0->0.25P->0.5P-> 0.75P->P (72 hrs)->0.75P-> 0.5P-> 0.25P->0	1st cycle: 0->0.25P->0.5P-> 0.25P->0 2nd cycle: 0->0.25P->0.5P-> 0.75P->P (72 hrs)->0.75P-> 0.5P-> 0.25P->0
Settlement of loading test	(i) Total settlement = P/AE + D/120 + 4 mm (ii) Residual settlement = D/120 + 4 mm; and 25% of the maximum pile head settlement during the test, whichever is the greater. where: D = Diameter of circular pile in mm, or = The least lateral dimension of steel 'H' pile section in mm (for driven steel 'H' pile ) P = 2WL Test load L = Nett length of pile (For piles with rock sockets, L shall be measured to the center of the rock socket.) A = Cross sectional area of pile E = Young's modulus of pile given below:	Same as ArchSD’GS

Reference:

1.   Particular Specification for Jacked Steel H-piles, issued by ArchSD;

2.   Development of Jacked Piling in Hong Kong by Victor Li & Joley Lam (2001);

3.   Code of Practice for Foundation issued by BD;

4.   Engineering Manual issued by BD;

5.   Termination criteria for high-capacity jacked and driven steel H-piles in Hong Kong Postgraduate Thesis, HKU

Other reference:

1.   HKU Scholars Hub – search “jacked pile”;