CHAPTER 11

CONSTRUCTION PLANNING

11.1

Introduction

11.2

Construction Procedure

11.3

Plan for Materials

11.4

Work Executing Plan

11.5

Safety Plan

11.6

Construction Schedule

 

11.1 INTRODUCTION

The advantages of GRS-RW should be fully incorporated while establishing a construction plan, This is done by matching the configuration and quality of structure under design with the topography and geology of the site.

 

The construction plan should allow a project to proceed smoothly, safely and economically.

Therefore, the construction plan takes full advantages of the design conditions, purpose of the structure, and construction technique. The existing site conditions and problems should be identified such that it exerts minimum effect on the traffic flow around the area.

The following items are considered for construction planning:

a) Topography, geology, climatic conditions

b) Plan for material and temporary site storage/office

c) Plan for construction method and machinery

d) Construction management plan

e) Schedule and plan for the staffs

f) Safety and sanitation management plans

g) Others (such as observational plan for GRS-RW that depends on the time of construction and site conditions)

 

11.2 CONSTRUCTION PROCEDURE

The construction procedure for GRS-RW using the RRR method is considered in order to allow a project proceeding smoothly and accurately. The procedure is decided by considering the details of project and construction conditions of the site.

The construction procedure for the RRR method is shown in Table 11.1 followed by explanations:

 

Table 11.1 Construction Procedure

1.

Preparation works

2.

Excavation and ground leveling

3.

Facing foundation construction

4.

Facing construction (embedded portion)

5.

Slope excavation conducted in stages

6.

Geosynthetic installation

7.

Temporary support for wall face using gabions

8.

Backfilling (proceed to 5 until the targeted wall height)

9.

Facing installation

10.

Additional finishing-up works of the surrounding area

 

 

Explanations (see Figure 11.1):

1. Investigation and confirmation of existing buried structures, surveying, ground clearing

2. Excavating and leveling of foundation for the GRS-RW

3. After attaining the specified base elevation of GRS-RW, excavation for the facing foundation is started followed by construction works.

4. The steel reinforcement and form for the embedded portion of facing is installed followed by concrete placement.

5. The existing slope is excavated in several stages, each of a specified height.

6. The geosynthetic layers are installed.

7. The gabions or other materials having high drainage capability are used as temporary support for the wall at 30 cm vertical spacing. The geosynthetic layer is wrapped around the gabions.

8. The backfill soil is spread and compacted.

Procedures 5 to 8 are repeated until the full height of the wall is reached.

9. The steel reinforcement and the form for the facing are installed followed by concrete placement.

10. The drain channel is constructed in front of the facing. Other cleaning-up works are then proceeded.

 

 

11.3 PLAN FOR MATERIALS

The materials used in construction, their specification, configuration, size, quantity, etc., should be decided based on the given design. The supplier, method and date of delivery, should be identified in accordance with the project plan.

1. Backfill soil

2. Facing

3. Geosynthetics

 

Backfill

As mentioned in Section 4.3, the backfill soil should be compacted to a density specified in the design draft. The soil having extremely large grain size or that has a potential to damage the geosynthetic, or that may not allow effective interlocking, should be avoided.

 

Geosynthetics

In addition to specification, configuration, size and quantity, the following issues should also be considered.

a) Time when it is to be installed

b) The Handling within construction site

c) Availability of storage yard and method of storage

d) Safety measures

The geosynthetic is weak against ultra-violet ray, and therefore, long-term exposure should be avoided by having a relevant storage yard. The nonwoven geotextile retains water and should not be exposed to rain.

11.4 WORK EXECUTING PLAN

The executing plan ensures that a project is carried out safely and effectively according to the construction procedure.

 

1. A work executing plan considers the following issues:

a) The scale of project and working environment

b) The type of backfill material

c) A combined use of construction machineries

d) Construction schedule and time

e) Construction environment (sound pollution, vibration, buried structures, overhead utility lines, etc.)

2. The RRR method is normally employed at the site with limited space. Because of the high embankment height, it is important to ensure that heavy machineries are not used close to the edge of temporary support. The light machinery should instead be used. Therefore, the scale of project and working environment are considered during planning stage.

3. In the RRR method, if an inappropriate machinery is used, the soil will not be compacted up to the desired properties. The required strength will not be attained for the soil and the voids present in it will lead to settlement. Therefore, the selection of machinery, method of soil spreading, number of passes, speed of construction, etc., should be considered.

4. The RRR method has the advantages of allowing construction at very limited space. To improve the efficiency of construction, construction safety and environmental conservation should be considered in addition to other various measures. The authorities related to buried structures, overhead utility lines, etc., should be consulted in establishing a work executing plan.

5. The width of road, weight limit, and other traffic constraints/regulations should be considered for the machineries used in the construction and transport of materials. The sound pollution, vibration, and other possible environmental hazards against neighborhoods should be avoid.

6. The manufacturing and handling of gabions, which are used as face support, should not be totally dependent on labor since the work efficiency will be greatly reduced. The fabrication of gabion machinery, working yard, transportation to storage yard, etc., have to be considered.

 

11.5 SAFETY PLAN

The safety plan is required so that a project will be carried out safely and effectively according to the construction procedure.

 

1. For the RRR method used with an existing highway and railway, or adjacent to an existing structure, qualified watchmen should be allocated to control the traffic.

2. In case of construction during rainfall, the GRS-RW should be covered with water-proof sheets.

3. The presence of cracks in the soil or large deformation of the gabions during construction should be reported immediately to the supervisor. The construction should also be stopped immediately. Subsequent instructions of the supervisor should be followed.

4. The guardrails or handrails must be installed at high locations, such as the crest of GRS-RW, to prevent human or machinery from falling down.

 

11.6 CONSTRUCTION SCHEDULE

The construction schedule is required so that a project will be carried out smoothly and effectively following the construction procedure and construction method.

 

The total amount of work can be estimated as the product of working days and expected amount of daily work.

The working days should exclude holidays, days when work is impossible due to natural, social and environmental conditions. Days for making plan, etc., should be excluded while calculating for the working days. For regions with heavy precipitation, the total working days have to be estimated properly by considering snow and rainfall. The amount of daily work is the work per machinery in a day.

 

  

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