Updated Method Statement for Sand Filling of φ3.0m Steel Tubular Piles (Rev.3)

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2 Doc. No. : PMBP-MBEC-MS-GZ008 Rev. No.: 3 Date: 24 May 2016 Updated Method Statement for Sand Filling of φ3.0m Steel Tubular Piles (Rev.3) 3 24 May 2016 XSK Third Issue XPA PJ LJH 2 07 May 2016 XSK Second Issue XPA PJ LJH 1 19 Nov 2015 XSK First Issue LB YBJ LJH Revision Date Prepared by Description Checked by Approved by Project Approved STATUS (latest revision): 3 Total no of pages (Excl Att): 10

3 Contents 1. Project Brief General Description of the Sand Filling Proposals Simulation Test of the Sand Filling and Compaction Construction Procedures of Sand Filling Works Detailed Description of the Sand Filling Procedures Quality Control Measures... 7

4 1. Project Brief Padma Multipurpose Bridge Project (PMBP) has totally 40 nos. main bridge piers in the river in which each pier has 6 nos. raked steel tubular piles with outer diameter Φ3.0m along the circumference, having rake of 1:6 and wall thickness 60mm. All the top elevation of steel tubular pile is +1.75m PWD. The toe elevation of P2~P12,P26~P41 is -114mPWD while the toe elevation of P13~P25 is -98mPWD.The PMBP has totally 240 nos. steel piles in which the piles with pile length L=117.35m are 162nos. while the piles with pile length L=101.13m are 78nos. Furthermore there are another 2 nos. constructability piles TD 5 and TD 6 having length of L= Apart from the main bridge piers as above described, about 2km downstream of main bridge alignment there are additional 7 nos. foundations for 400KV transmission lines, and each pier has 3 nos. raked steel piles with same parameters as P13~P25. In accordance with the provisions as stipulated in the design drawings for Φ3.0m constructability trial piles and working piles for main bridge, after completion of tremie concreting (10m bottom concrete plug), base grouting and removal of base grouting tube and centralizing frame, sand filling works shall be carried out. As per the design drawings provided by AECOM, the sand plug length in the steel tubular piles will be 87m (P2~P12 & P26~P41) & 71m (P13-P25), with total sand volume of 570cum (P2-P12 & P26-P41) & 470cum (P13-P25) respectively. 2. General Description of the Sand Filling Proposals The sand filling works will use the river sand in the vicinity of pier location. It is proposed to use dredgers or air lifting reverse circulation method to take the sand from the river. The river sand will be filtered and cleaned by use of sand purifier, and then be filled into the steel tubular pile slowly. River sand filled into the steel tubular pile will be compacted through vibrating compaction method until the design top level in the pile is reached. 1

5 3. Simulation Test of the Sand Filling and Compaction The Contractor has carried out the simulation test of the sand filling and compaction procedures on 18 April 2016 to verify the effectiveness of the vibrating compaction method. In the course the simulation test, the following procedures are followed for vibrating and compaction of sand: No. Procedure of compaction period 1 start the vibrator & maintain vibrating for 2min 2 min Using floating crane to raising the Vibrator about 0.4m for the 2 3 first time (vibrator keeps vibrating state), and then stop raising but vibrator keeps vibrating Then continue using floating crane to raise the Vibrator another 0.4m (vibrator keep vibrating), and then stop raising but vibrator keep vibrating After the vibrator has been pulled up by 0.4m+0.4m, proceed with filling sand into the pile and repeat the above procedures until completion of the simulation test. After completion of the test, the top 1m sand plug was removed, and the Contractor took total 10 groups of sand samples at the locations shown in the Figure ? Fig.1 Location of Sand Samples Taken by the Contractor The compactness of the 10 groups of samples through test are 97.71%, 97.80%, 98.88%, 98.77%, 2

6 98.68%, 98.39%, 97.99%, 95.27%, 96.86% and 98.61% respectively (compared with maximum dry density), which meets the requirement that the compactness of sand plug shall over than 95%. Please kindly refer to Attachment No.1 Compaction in Pile with Dredged Sand for details. Therefore, the Contractor proposes to use the procedure of simulation test for the sand filling works of constructability piles and the subsequent working piles. 4. Construction Procedures of Sand Filling Works The main procedures of sand filling works for steel tubular piles include: 1) Preparation for sand filling works, 2) Pump the river sand in the vicinity of the pier location by use of dredgers or air lifting reverse circulation equipment to the purifier for cleaning (the function of the purifier is to separate the small size particles from the river sand), 3) Open the bottom outlet of the purifier to fill the sand into the steel tubular pile, each time 2m, with volume about 13cum, 4) Vibrate and compact the sand as per the following procedures. No. Item Period 1 start the vibrator & maintain vibrating for 2min 2min Using the 10t winch to raising the Vibrator about 0.4m for the first 2 3 time (vibrator keeps vibrating), and then stop raising, but vibrator keeps vibrating Then using the 10t winch to raise the vibrator another 0.4m (vibrator keeps vibrating), and then stop raising, but vibrator keeps vibrating 5) Repeat steps 2~4 until the compacted sand reaches the designed top level 5. Detailed Description of the Sand Filling Procedures 1) Preparation Works for Sand Filling Works Mobilize the sand suction dredger and flatbed barge to the pier location in advance, then extend the sand suction pipe of the dredger and install a 10t winch on the flatbed barge. Use floating crane to lift the vibrator and the guide frame into the steel tubular pile, then the vibrating component of the 3

7 vibrator will be lowered to the level that is 0.3m above the bottom concrete plug by use of the 10t winch. After the vibrator and the guide frame are put into place, use floating crane to lift the sand purifier onto the working platform, and connect the sand pipe of the dredgers with the inlet of the purifier. Please kindly refer to Figure 2 for the details of the sand filling structure. Fig.2: Sketch for Location of the Sand Filling Equipment Fig.3 Sand Purifier 4

8 Fig.4 Guide Frame of the Vibrator Fig.5 Vibrator 2) Taking Sand from the River Pump the river sand by use of the dredgers or air lifting reverse circulation method into the sand purifier for cleaning. The sand/water mixture will rotate centrifugally with a certain rate in the energy dissipation facility, impurities and water in the mixture will flow out through the drain hole, and the clean sand will fall into the purifier under gravity. When the sand in the purifier reaches the level of 0.2m from its top, shut down the sand suction equipment to terminate pumping sand into the purifier. At this moment, the volume of sand in the purifier will be about 34.5 m³. 5

9 3) Open the Outlet of the Purifier and Fill Sand into the Steel Tubular Pile Open the outlet at the bottom of the purifier, and fill about 2m high sand into the steel tubular pile each time. There are two methods for measuring the height of sand filled into the steel tubular pile: Install a sleeve on the diaphragm of the guide frame which will inserted with a measuring rope (diameter of the sleeve is bigger than that of the measuring rope, but smaller than that of the plummet), and use the measuring rope to measure the height of sand in the φ3.0m steel tubular pile. Use the scales made inside the purifier for calculation of the height of sand filled into the steel tubular piles. The volume of sand filled into the steel tubular pile is about 13cum. Please kindly be informed that method 1 will be the first choice for measuring the height of sand filled into the steel tubular pile, and method 2 will be used as a supplementary measure. According to the saying from CSC Engineers, the rate of sampling frequency should achieve to be 10m (filling height) /time, namely 65m3/time. The sand samples will be delivered to the laboratory for inspection and test. In the meantime, the sand vibrating and compaction process shall be kept going on, and shall not be suspended. 4) Vibrating and Compaction of the Sand Vibrate and compact the sand as per the following procedures. No. Item Period 1 start the vibrator & maintain vibrating for 2min 2min Using the 10t winch to raising the Vibrator about 0.4m for the first 2 time (vibrator keeps vibrating), and then stop raising,but vibrator keeps vibrating 3 Then using the 10t winch to raise the vibrator another 0.4m (vibrator keeps vibrating),and then stop raising,but vibrator keeps vibrating Due to compaction of the sand, the height of the sand in the steel tubular pile will reduce continually. According to the simulation test, the volume of sand will be reduced by about 1/4 after being compacted, please kindly be informed that it is only the phenomenon observed during 6

10 the simulation test, and should not be used as the basis or reference to assess the height or compacted of sand during actual sand filling in the Piles. During the actual sand filling process, MBEC will use the measuring rope to survey and check the actual top level of sand in the piles. 5) Repeating the Filling and Vibrating Process of Sand When the embedded depth of the vibrator in the compacted sand (measured by measuring rope) is less than 40cm, open the outlet of the purifier to fill another 2m high sand into the steel tubular pile, Repeat the above 4) described procedures until the sand in the steel tubular pile reaches the designed top level. 6. Quality Control Measures 1) Make scales inside the sand purifier. For easily measuring the volume of river sand filled each time, it is proposed to make scales inside the purifier by using white paint. The volume of sand filled into the steel tubular pile and the sand remained in the purifier can be easily figured out through the change of scales inside the purifier. 2) In order to make sure that the sand inside the purifier can fall down smoothly after opening the outlet, it is proposed to install two nos. of external vibrators on the outlet, accompanied by using water jetting, to increase the falling speed of the river sand. Fig.6: External Vibrator and Water Jetting Valve attached to the purifier 3) After the river sand being pumped into the sand purifier by use of sand suction equipment through energy dissipator, the water/sand mixture will form an Annular Flow inside the 7

11 purifier, the river sand and impurities in the sand (soil, etc.) will be separated due to the Annular Flow. The clean sand falls down to the bottom of the purifier, and the impurities in the sand are discharged through the drain hole. Two nos. of hose pipe will be connected to the drain hole for collection of the impurities, and then discharge all the impurities collected together. Fig.7. Annular Flow in the Purifier Fig.8: Hose Pipe for Discharging Impurity/Water Mixture 4) In order to pull up the vibrator each time by about 40cm, it is proposed to make scales on the 10t winch in advance, and make marks on the wire rope of the winch at intervals of 40cm. 5) During the simulation test of sand filling works carried out for TD5, the electrical cables for the guide frame and the vibrator were not intertwined during the vibration process. However, special attention shall still be paid to the electrical cables for the guide frame and the vibrator to avoid any intertwining phenomenon of the cables. 8