METHOD STATEMENT Gói thầu 4 Xây dựng Hệ thống cống cho một phần khu vực Hà Đông và Khu đô thị mới Trình lần cuối Biện pháp thi công gia cố nền đất bằng vữa hóa chất Công trình Cấp thoát nước cho nhà máy Yên Xá.
Trang 1TABLE OF CONTENTS
Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
Trang 21 Overview
1.1 Purpose
In pipe jacking technology, the difficulty of construction work depends on the geological conditions Especially, in the cases that strata in unstable, excavation is vulnerable to collapse, ground is vulnerable to subsidence, or there will be the requirements of protecting underground structures or reinforcing the stability of receiving shaft, the ground improvement to the sides of shaft is very necessary.
The method of ground improvement by chemical is one of the treatment solution for improving the mechanical properties of soil with the main purpose of reinforcing the soil structure and mitigating the penetration of groundwater This is a ground improvement method with the preeminence of its simplicity and convenience compared to other improvement methods.
Chemical ground reinforcement utilizes the chemical solution that their setting times can be adjusted optionally then injected by pressure into the ground through the pipes arranged in ground for blocking ground water and reinforcing to ground structure The features of this improvement method are as follows:
a Chemical solution will dispose the existing ground water occupied in the cavities of soil then solidifies at the gaps between soil particles, but without changing the strata.
b With the penetration and solidification of this chemical solution, the soil will has its better cohesion, lower porosity, consequently the ground shall become more solid and lower permeable.
c Chemical improvement solution consists of main materials as liquid glass (SiO2 / Na2O), setting admixture, and other auxiliary materials, which can be mixed in various proportion so that the setting time of mixed product can be adjusted in a range from few seconds to hours.
Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
Trang 3No Route From
Shaft Shaft To
Number of departure shaft
Number
of arrival shaft
Number of intermediate shaft
1.3 Principle of the method of ground improvement
- Depending on the purpose and characteristics of the soil, the suitable method and materials shall be applied The double pipe strainer method (multi-phase) shall be applied for this work.
- The double pipe trainer method will be applied via two steps, after completing the drilling work into ground with a cutting blade jointed a special drill bit:
o Primary injection: In first step, the fast setting solution (15 seconds) will be pumped to fill into the saturated cavities in the ground in purpose of making the ground homogeneous, forming an osmotic area, where the chemical pumped in stage 2 can penetrate easier.
o Secondary injection: slow freezing solution will be pumped in second step to penetrate into the firstly pumped area At that time, groundwater will be pushed out
of the reinforced area and concurrently the foundation will solidified.
- Depending on the setting time of solutions, the products of the double pipe strainer method will have their different properties Thanks to the adjustment in pumping ratio of 1st and 2nd steps, the ground improvement will bring a reliable effective for various kind of soil such as clay, macadam or multi-layer soil.
Flash setting chemical fill the void around
rod, water channel and layer void to stabilize
the ground and the chemical material forms
primary penetration area.
Secondary injection of slow setting material forms secondary penetration area Longer gel time enables minute penetration with low pressure.
Trang 4Flash setting chemical
Filling the gap around the rod
Filling water channel and layer gap
Primary penetration area
Primary injection
Double pipe rod
Special tip unit
Slow setting chemical
Primary penetration area
Secondary injection
Trang 52 Specification, standard and relevant documents
2.1 Specification and standard
Technical requirements regarding to this method statement for soil improvement by chemical grouting include, but are not limited to the following:
- The Specification – a part of the Contract;
- Standards of Micro tunneling Technology for Vietnam;
- Japanese pipe jacking standard;
- Chemical grouting work – Design guide (version 2019) of Japan Grout Association.
2.2 Relevant documents
Drawings relating to the method statement for soil improvement by chemical grouting include, but are not limited to, the following:
- Drawing number P4-R-CM-JW-005, P4-R-CM-JW-005 in Technical design drawing;
- Working drawing of plan and profile of sewer pipe;
- Working drawing for shafts;
- And other construction drawings.
- This method statement shall be read in conjunction with the method statement for pipe jacking construction and method statement for shaft construction.
Trang 6- Site fence shall be installed in accordance with construction permit.
o Layer 2: Stiff to very stiff brownish grey-reddish grey-greenish grey Clay;
o Layer 3: Stiff brownish grey reddish brown sandy Clay;
o Layer 4: Firm brownish grey-yellowish grey sandy Clay;
o Layer 5: Soft to firm dark grey brownish grey sandy Clay, somewhere mixed with Organic matter;
o Layer 6: Loose to medium dense grey - dark grey fine to medium Sand, somewhere interbedded with clayey sand lens;
o Layer 7: Soft to firm brownish grey yellowish grey, dark grey sandy Clay, somewhere mixed with Organic matter;
According to technical design document, sewer pipeline is located in the layer: Loose to medium dense grey - dark grey fine to medium Sand, somewhere interbedded with clayey sand lens;
Trang 7Boring log tipical
ThÝ nghiÖm SPT
>50 50 40
10 20 30 (m)
Tû lÖ 100
Tê sè
1/ 1/1
X: 2319262.34 Y: 582309.29
Trang 8Đội thi công/ Construction team
Giám sát an toàn Safety supervisor
Kỹ sư chất lượng Quality Engineer
Kỹ sư công trường
Site Engineer
Qản lý an toàn Safety Manager
Quản lý chất lượng Quality Manager
Quản lý xây dựng
Construction manager
Giám đốc dự án Project manager
Package 4: Construction of Sewer Pipes in Ha Dong
Trang 9Package 4: Construction of Sewer Pipes in Ha Dong
Trang 10Package 4: Construction of Sewer Pipes in Ha Dong
- Installing fence for construction site according to the issued construction permit.
- Using total station combined with steel ruler to determine the improvement line, improvement segment on the ground.
- Checking and locating utility items.
- Storing and preserving materials properly in the designated areas.
b Equipment mobilization and installation
- Construction materials and equipment will be mobilized to the site according to the requirements of each construction phase.
- Installing drilling equipment on site.
- Connect the drill and necessary pumping equipment, mixing (such as drill rod, control panel, drill bit, ) to inject the mortar.
c Drilling
- Set up the machine, start drilling holes (drill down to the designed position).
Trang 11Package 4: Construction of Sewer Pipes in Ha Dong
Trang 12Package 4: Construction of Sewer Pipes in Ha Dong
- Chemical injection shall be done 2 steps.
- Materials for the 1st injection are fast freezing Silica shot (inorganic solution) Standard formulation for rapid hardeners: Silicarizer (RMG - S2) Solution A and solution B will
be mixed continuously during the mixing process.
- Value of main material for Silicalizer
Evaluation standard: 64TCN 38:1986 and JIS K1408-1966
starch syrup
An Xuan Thinh – Song Da 9 Joint Venture Page 12/26
Trang 13Package 4: Construction of Sewer Pipes in Ha Dong
Setting time: less than l0 seconds
- Materials for the 2nd stuffing are slow freezing Silica shot (inorganic solution) Standard formulation for slow hardeners: Silicarizer (RMG - L3).
SILICARIZER RMG-L3 Long setting blend (per 1000 litter) Agent A
Setting time: less than 24h.
Note: the reagent used is 70-75% sulfuric acid.
e Chemical injecting
- After completion of hole drilling, injecting work will start from bottom up.
- The grouting at the site will be controlled through the pressure shown on the pump manometer (0.6Mpa).
- Injecting will be done in 2 steps Height of each injection step: h = 0.25m or 0.5m.
- Start injecting for primary step: fast freezing solution shall be used to fill the empty gap around the pumping tube.
An Xuan Thinh – Song Da 9 Joint Venture Page 13/26
Trang 14Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
- Secondary step: slow freezing shall be used to penetrate into the ground.
- The injecting speed is adjusted within 8 ~ 16l / min.
- Completion of injecting work: Raise step by step, repeat the 1st step, 2nd step in sequence to the end of working process.
An Xuan Thinh – Song Da 9 Joint Venture Page 14/26
Trang 15Package 4: Construction of Sewer Pipes in Ha Dong
5.5 Volume of injecting chemical
Quantity for injection of chemical grout shall be determined via formula as follows
Q = V x λ
In which:
Q: Injecting quantity for improvement area (m3 or litter)
V: Volume of improvement area (m3).
λ : Injecting ratio (%) – based on standard: Chemical grouting work – Design guide (version 2019) of Japan Grout Association, injecting ratio shall be determine is as follows:
Type of soil
SPT Value (N)
Ratio pump via volume (%)
inject
Secondary inject Sand mixed
gravel
An Xuan Thinh – Song Da 9 Joint Venture Page 15/26
Trang 16Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
- The volume of chemical grouting at the shaft shall be shown detail in working drawing and submitted separately period to starting work on site.
5.6 Construction durations
Construction schedule depends on the type of soil, deep and thickness of improvement area.
Basically, the implementation progress is as follows:
2-3 points/ shift (8 hours) Improved deep > 8m
6 Manpower, equipment and materials to be used
6.1 Manpower
The expected manpower for the construction of ground improvement by chemical mortar at 1 construction location is as follows:
holes
The above-mentioned manpower amount is only expected, depending on the work requirements of each construction phase, the Contractor will mobilize the appropriate number.
An Xuan Thinh – Song Da 9 Joint Venture Page 16/26
Trang 17Package 4: Construction of Sewer Pipes in Ha Dong
is as per the following table:
Machine name Type and features Wattage
Drilling machine
Hydraulic machine, drilling capacity: 100
~ 200m, rod diameter 40.5mm
Pump for seal
An Xuan Thinh – Song Da 9 Joint Venture Page 17/26
Trang 18Figure of drilling machine D2-JS
An Xuan Thinh – Song Da 9 Joint Venture Page 18/26
Trang 19Figure of mixing machine SL-3000
An Xuan Thinh – Song Da 9 Joint Venture Page 19/26
Trang 20Figure of mortar pump NPOT-40
Figure of mortar pump NPOT-40
Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
Trang 21
Figure of flow meter
Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
Trang 227 Quality management
7.1 Material:
Materials for ground improvement must be obtained the Engineer's approval and the
Employer's approval, the supplier will transport the materials directly to the site.
At construction sites, quality control is carried out in the following table:
Notes: ○ ＝ Contents to be done
The raw material storage method must be structured to avoid leakage, dispersion and penetration In addition, it is necessary to store at the area to facilitate construction work as well as to manage to avoid theft.
Confirm the amount of solution during construction: To check the frozen state of pumped materials, before construction and during construction (once in the morning, once in the afternoon), it is necessary to check and Confirm amount of mixing.
7.2 Checking construction position, drilling length
Marking, accurately measuring the drilling point according to the designed position in working drawing.
Site engineer and the drilling operator are responsible for performing the drilling with the position tolerance does not exceeding 5cm Each hole will be numbered and recorded, this number is used to control quality.
The drilling length depends on the surface where the machine is located, designed level for ground improvement, thereby determining the depth.
Need to, check the elevation of the machine and and ground surface at construction area to determine the detail depth.
7.3 Check the incline and the depth during drilling
All drilled holes must be checked in depth A check of the depth of the hole is based on the length of the drill rod and the benchmark located on the ground, which is done by the site engineer and the operator The length of the drill rod is calculated as follows: (number of rods) x (length of 1 drill rod) + (length of drill blade + drill head).
Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting
Trang 23When installing the machine, it is necessary to use a level ruler to fix and ensure the verticality of the machine.
The incline angle of the drill rod will be measured and the site engineer and the drill operator will regularly check the vertical and inclination angle of drilling rod.
The drilling rod must be enough and be placed near the drilling machine.
7.4 Injecting volume control and completion accepting for soil improvement work
Injecting flow and pump pressure will be controlled by the flow meter and manometer on the pump, data processed and displayed on the control board All information will be recorded automatically.
The content of daily injecting control is shown in the following table:
Discharge
pressure gauges
Stop pump when abnormal situation occurs and determine the
cause
When the pump pressure reaches the designed value (0.6Mpa), it will move on to the next step even if the design volume has not been reached.
The soil improvement work shall be considered complete and ready for acceptance when: i) The injecting chemical for all points of tunnel eye of the shaft are completed;
ii) All inspection as mentioned in sections 7.1 to 7.4 of this method statement are done, including sufficiently their related documents.
7.5 Control the erupting ground
The arising of the eruption ground when pumping chemical solutions affects the existing buildings So it must be avoided.
When pumping chemical solution, it is necessary to measure the current status and the elevation of the road surface, manage and monitor the pump pressure and flow, when there
is an abnormal situation, it is necessary to stop construction work immediately, adjust the pump flow again and setting time avoids the high pump pressure and pavement lift.
8 Safety control
Package 4: Construction of Sewer Pipes in Ha Dong
submission
Method statement for soil improvement by chemical
grouting