3 thuyetminh pvd and phdok

Installation of pot bearing GMS Ben Luc Long Thanh Expressway Project Package A5 Civil Works Km 32+450 to Km 35+900 SOFT SOIL IMPROVEMENT MEASURES METHOD STATEMENT OF PREFABRICATED VERTICAL DRAINS (PV[.]

SOFT SOIL IMPROVEMENT MEASURES

METHOD STATEMENT OF PREFABRICATED VERTICAL DRAINS

(PVD)

TABLE OF CONTENTS

I INTRODUCTION

II RELEVANT SPECIFICATIONS, STANDARDS AND DOCUMENTS

III SITE ORGANIZATION

IV CONSTRUCTION PROCEDURE

V RESOURCES TO BE USED

I INTRODUCTION

This “Method Statement” describes soil improvement works, using PVDs at GMS Ben Luc – Long Thanh expressway project – Package A5 civil works

This statement consists of construction procedure, materials, manpower, equipment, management quality control and schedule to complete the works according to Design documents and Specification of this project

1 Work scope

This method statement includes the following work scopes:

i)

PVDs Installation ii) Horizontal drains (PHD) Installation

iii) Separation geotextile

2 Working drawing

Prior to commence the work each area, Working Drawings will be submitted for the Engineer separately Designated areas for the works will be shown in Working Drawing separately submitted in due course Typical cross section drawings are attached to provide general view

RELEVANT SPECIFICATIONS AND STANDARDS

ASTM D1621 Standard Test method for Compressive Properties of

Rigid ellular Plastics ASTM D3776 Standard Test method for Mass Per Unit area (Weight)

of Fabric ASTM D3786 Standard Test method for Bursting Strength of Textile

Fabrics – Diaphragm Bursting Strength Tester Method ASTM D4491 Standard Test method for Water Permeability of

Geotextiles by the Permittivity method ASTM D4533 Test method for Trapezoid Tearing Strength of

Geotextiles ASTM D4632 Test method for Breaking Load and Elongation of

Geotextiles (Grab Method) ASTM D4716 Test method for Determining the (In-plane) Flow Rate

per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using Constant Head

ASTM D4751 Standard Test Method for Determining Apparent

Opening Size of a Geotextiles ASTM D4833 Test method for Index Puncture Resistance of

Geotextiles, Geomembranes, and Related Products ASTM D5101 Measuring the Soil-Geotextile ystem Clogging Potential

(By the Gradient Ratio) ASTM D5321 Standard Test method for Determining the Ceofficient of

soil and Geosynthetic or Geosynthetic and Geosynthetic Friction by the Direct Shear Method

ASTM D5567 Hydraulic Conducivity Ratio (HCR)Tesing of Soil/

Geotextiles Systems

III SITE ORGANIZATION

Site organization for this projectis shown below

Environment &

Safety Engineer

Project Manager

Construction Manager

Site Engineer

QC Manager

Team for PVD work

IV CONSTRUCTION PROCEDURE

1 Work flow-chart

Construction procedure for soil improvement work by Prefabricated vertical drains (PVD) method is shown in Flow chart for construction as below:

\

2 Work procedure

The work procedure is described as follows

2.1 Site preparation

The soil surface shall be leveled and then temporary facilities will be set up for construction

Preparation of utilities including electricity, water and light at required positions will

Construction preparation, install geotextiles

Install PHD

Laying high strength geotextile

Set monitoring equipment

Install PVD

Sand filling Test and Acceptance

Monitoring Information Fill as working platform

be implemented

Prepare machineries maintenance, labor allocation, site layout, material storage, temporary facilities, fire alarms and drainages

Products and semi-products are tidily stored in warehouses and separated by tags or signs

Miscellaneous materials such as hardware and welding supplies shall be stored in the warehouses and managed by a material staff

Machine, equipment and material should be ensured in good quality and supply on time

2.2 Installing separation geotextiles

Installing non-farbric geotextiles along heart line

a) Construction procedure

- The jobsite shall be completely cleared prior to the placement of geotextiles, in particular, the removal of garbage, sharp or rigid chunks

- Each reel of geotextiles has the dimension of 6m  100m Carts are employed to mobilize the geotextiles to the correct work site

- The geotextiles are placed by humans A reservoir for deformation or twist is accounted for

- An overlapping not less than 30cm is needed, and sewed by portable or special sewers

- The performance of geotextiles shall be supervised by a special person

- As the geotextile gains weight if damped or soaked, the placement shall be placed by preventing from rainfalls and water

b) The non- fabric shall be meet the requirement as table bellow

- Non-woven Geotextiles sheets shall be UV-stabilized, made of 100% polypropylene yarns which may be mechanically or thermally bonded from continuous filament

- The tensile strenght shall be more than 12kN/m to ASTM D 4595 in both directions at the breaking elongation of not more than 40% puncture resistance to

ASTM D 4833 shall be at least 350N.

2.3 Sand filling stage 1

Sand is transported to required positions, fill to layers to 1 m level, flattened and compact as request

2.4 Installation of Prefabricated Vertical Drains (PVDs)

The construction flow of PVD is shown as below:

Prefabricated vertical drains (PVDs) shall be installed throughout the soft soil layers; Table 4.1 shows the main properties of PVD material to be used

Table 4.1 Required characteritics of PVD matterial according to “Technical

specification for soil improvement- Technical design documents”

Designation

Requirements VN standard

22 TCN262-2000

Apparent Opening Size

(AOS) O95, μm

ASTM D 4751-87

Less than 75 Less than 75

Grab Tensile Strength, kN

(longitudinally only)

ASTM D 4632-91

Greater than 1 Greater than 1

Discharge Capacity (m3/yr)

at 1 day, 200kPa and

hydraulic gradient i of 1

ASTM D 4716-87

Greater than 500

Applied pressure

of 350kPa Permeability of filter, m/sec ASTM D Greater than Greater than

Marking of PVD

Trial penetration of PVD

Mass construction of PVD installation

4491 1 x 1 x

Catalogue of PVD material shall be submitted for approval before purchasing and supplying for installation in soil improvement areas with spacing and penetration depth according to the Technical Design

a) Technical requirements for PVD installation

PVD material shall be stored in the warehouses to protect from rains, sunshine and ruins PVDs with any defects are strictly not allowed to use

Extension of PVD shall be implemented by opening the filter cover and overlapping (≥300 mm) the core, then wrap and staple to ends

Tags shall be used to locate the installation points

PVD installation is presented as below:

- Use ruler or marked line to measure the spacing and points with deviation of

±100 mm

- PVDs are arranged in triangular pattern The inclination of vertical installation shall be less than ±5%

- About70cm length of PVDs shall be remained above the surface of back filling layer then shall be connected with the horizontal pipe

- PVDs shall be installed by static pressing or vibration method

- After completion, self-confirmation shall be executed Once confirmed, the work

is reported to the Supervisors

b) Marking of Vertical Drain

After coordination survey work, the all vertical drain points will be demarcated using bamboo chopsticks and any other materials to mark the points Tolerance shall

be within 100 mm at this moment.The horizontal and vertical tolerance is 5%; the depth tolerance is 1%

c) Trial Penetration of Vertical Drain: Calibrate monitoring unit

Mobilize Vertical Drain Rig to the marking location Then, set

up the Plastic Band Drain to the Rig

Then, Vertical Drain will

be pulling out from the casing pipe and marking each one (1) meter for checking the monitoring unit

After the marking, band drain will be re rolled for their installation

Then, trial penetration work will be done slowly to check and adjust monitoring unit and actual penetration depth (calibration)

After the calibration of monitoring unit, we will continue trial penetration to check the treatment thickness

Then, the vertical drain length will be recorded and submitted for approval Besides, trial PVD installation will be carried out at outside of treatment area for inspection by the Engineer

d) Vertical Drain Arrangement

All vertical drain shall be recorded to designated record format and submit these record with summary

- Mandrel :A mandrel (dimensions: 140x70x10mm), which is pushed downwards into the weak subsoil

- Set Anchor Plate :Set anchor plate (140x85mm) to band drain and reinsert to the casing pipe

- Penetration

Casing pipe will be penetrated into the ground until the designated depth Then, casing pipe will be return to the ground If vertical drain will be come back more than tolerance; Location within 100 mm, Verticality less than 5%, Depth less than 1%, vertical drain shall be re arranged

Splicing

Splicing of the PVD shall be done by stapling with proper workmanship ensuring the structural and hydraulic continuity of the drain At the splice the jacket of the upper part

of the drain shall be external to the lower portion A maximum of one splice per drain will be permitted without specific permission from the Engineer

The jacket and core shall be overlapped a minimum of 300 mm at any splice

Cut and Record

When casing pipe will be set back to original position, the plastic band drain shall be cut by knife Vertical Drain shall be remained at least 300 mm from the platform

Then, Anchor plate shall be arranged again

At the same time, the length of each vertical drain shall be recorded to the monitoring format Total vertical drain length will be calculated each day, cumulated and presented every day as a daily progress report

2.5 Setup Prefabricated Horizontal Drain

a) Requirement of Materials

The strip drain shall be a prefabricated type made up of a polymeric drainage core wrapped in a filter made of a non-woven fabric of continouns filaments of 100% polypropylene The core shall be fabricated with suitable drainage channels

Both filter and core structure should be strong and flexible, ablr to follow to topographical change without breaking and cutting The filter material should be reistant to clogging and the core structure able to resist heavy pressure, whilst still maintaining long term high level drainage ability.

Drain Criteria Standard

Compressive strength (min) 600 kN/m2 ASTM D162

Fabric

Grab tensile strength (min) 400N ASTM D4632

UV Resistance, 500hr 80% retained ASTM D4355

b) Placement of prefabricated horizontal drain

Prior to the installation of drains within the designated area the Contractor shall demonstrate that his equipment, method and materials produre a satisfactory installation in accordance with these specifications For this purpose, the Contractor will be required to install trial drains at locations designated by the Engineer

Drains will be located by the Engineer The location of the drains shall not vary by more than 150mm from the locations indicated on the Drawings or as directed by the Engineer

Splices or connections in the drainage material shall be done in a workmanlike manner and so as to insure continuity of drain material

2.6 Placement of High strength Geotextile

a) Construction procedure

Hightstrenght Geotextiles: Woven

The geotextiles sheets shall be UV- stabilized and made of polypropylene yarns

The ultimate tensile strenght to ASTM D 4595 shall be more than 20kN/m in both directions at the breaking elongation of not more than 20%

- The jobsite shall be completely cleared prior to the placement of geotextiles, in particular, the removal of garbage, sharp or rigid chunks

- Each reel of geotextiles has the dimension of 6m  100m Carts are employed to mobilize the geotextiles to the correct work site

- The geotextiles are placed by humans A reservoir for deformation or twist is accounted for

- An overlapping not less than 30cmis needed, and sewed by portable or special sewers

- The performance of geotextiles shall be supervised by a special person

- As the geotextile gains weight if damped or soaked, the placement shall be placed by preventing from rainfalls and water

V RESOURCES TO BE USED

Equipment to be used for the PVDs operation works are listed below

No

1 PVD installation rig ≥