What is Setting Out Work?
Setting out work refers to the technique of accurately marking the foundation or alignment of a project structure – such as a building, road, bridge, culvert, or tunnel at designated locations on the ground according to the design plans.
What are the two purposes of setting out?
The purposes of setting out are:
- Accurate Coordinate Determination: Setting out determines the exact location of structures according to the construction project plan, ensuring that all structures are built in the correct place and to the correct dimensions.
- Implementation of Design: Through setting out work, various elements of the project design can be accurately positioned, such as foundations, walls, and other structural components. This assists in the proper implementation of the project.
These two purposes ensure that construction activities are completed accurately and effectively.
Controllers of Setting Out Works:
In setting out works, two main types of controllers are required:
(1) Horizontal Controller
(2) Vertical Controller
Horizontal Controller
Horizontal controller stations must be established near the construction site. The horizontal controller is formed by a series of identifiable markers that follow the known plan position, from which the significant points of the planned structure are established. In the case of large structures, both first and second stage control points can be utilized (see Figure 3.1). Triangulation stations can be considered as first-stage control points. The second-stage control points are established following these control points. The coordinates of the second-stage control points are determined through the traversing process. The second-stage control points provide overall control of the area. Therefore, they must be located close to the construction site. However, it is preferable for the control points to be sufficiently distant from the construction boundary to prevent any damage during construction. In the process of determining the locations of these control points, the well-known principle of “Working from whole to part” is applied.
Vertical Control:
Vertical control is formed by the placement of identifiable markers at known heights relative to a specific datum plane. The heights of all points in the work area are typically reduced according to a nearby benchmark, commonly referred to as a Marker Benchmark (MBM). This master benchmark (+0.010m) is used to establish several transferred benchmarks or Temporary Benchmarks (TBM) for levelling accuracy. The locations of the TBMs must be precisely determined during the initial survey of the site. If possible, existing permanent features should be used as TBMs. Each TBM must be indicated by a number on the site plan and properly linked to the recognized MBM. All TBMs should be carefully preserved, and periodic re-checking is required at specified intervals. Additionally, the distance between any two TBMs should not exceed 100 metres.
What is the purpose of RTK GPS setting out?
The purpose of RTK (Real-Time Kinematic) GPS setting out is to determine very high levels of coordinates for construction and land surveying. Its main objectives are as follows:
- High Accuracy: Using RTK GPS allows for extremely precise coordinate determination within 2 centimeters, which is crucial during the setting out process. This ensures that construction materials are placed correctly.
- Rapid Data Collection: RTK technology provides real-time data, allowing for quick information retrieval for construction activities and saving time.
- Implementation of Design: RTK GPS assists in accurately placing structural components according to the project design, such as foundations, walls, and other structural elements.
- Operator Convenience: RTK GPS makes it easier for operators to use and provides them with accurate guidance on-site, reducing the likelihood of errors.
- Repetition: Through RTK technology, repeating previous work or constructing new structures in the correct locations becomes easier, accelerating the development process.
- Site Management: RTK GPS aids in site management by providing accurate data to monitor project progress and the status of completed work.
Through all these objectives, RTK GPS enhances the efficiency and accuracy of the setting out process.
Importance of Control Surveys
A control survey establishes reference positions on a piece of land or a construction site. These control points accurately identify and map features of the land or site, including buildings, roads, and utilities. Control surveys provide reference points that serve as the basis for various construction processes. Without a control survey, the construction process would be much more complex and time-consuming. Control surveys are also used to ensure that the project is built in a manner that complies with all regulations and standards. Additionally, surveyors must ensure that all points in the control network are accurately measured and recorded to prevent any risk of loss or injury. Without a control survey, it is impossible to determine whether the project has been constructed according to the necessary safety codes and regulations.
Control Survey is an important geodetic activity used for the accurate determination of land coordinates and mapping. Its significant aspects are as follows:
1. Accuracy: Control surveys provide highly accurate data for land infrastructure and engineering works. This aids in the correct design and implementation of construction projects.
2. Land Boundary Determination: Control surveys help determine the exact boundaries of land, which is effective in resolving land-related disputes.
3. Foundation for New Projects: Control points are established for new construction or development projects, creating a foundation for accurate future work.
4. Data Preservation: The data collected through control surveys is long-term and preservable, which may be required for any future project.
5. Development Planning: This is crucial for urban development and local infrastructure planning, as it provides information to local government and planning authorities.
6. Use of Technology: Modern control surveys utilize technologies such as GNSS (Global Navigation Satellite System), theodolites, leveling instruments, and others, which enhance accuracy.
Control surveys establish a foundation for precise and effective engineering work, which is beneficial for future development and management.
Underground Bench Mark
After determining the elevation of underground marks through vertical measurements, a leveling instrument is placed at the bottom surface of the shaft. Subsequently, a bench mark is established on a securely driven stake in the ground or alongside the tunnel. If the tunnel is within a rock mass, a permanent bench mark is installed on the extended portion that exists at the level of the rock mass.
Tunnel Project
A tunnel is a specially constructed conduit-shaped structure built underground. Tunnels are constructed for various purposes, such as in railways of large cities, highways, hydropower projects, and irrigation projects. They are primarily built to create a direct connection between two stations separated by a valley or a high hill, thereby reducing distance. However, tunnels not only reduce distance but also significantly decrease the excessive costs associated with slope destruction and maintenance, facilitating faster vehicle movement.
In a tunnel project, the following survey-related activities need to be carried out:
1. Setting Out Surface Surveys: This process involves conducting preliminary surveys through transit and stadia for an area extending from 3.22 km (2 miles) to 4.88 km (3 miles) on both sides of the proposed alignment. Detailed discussions on this can be found in Chapter 3 under the section on surface alignment.
2. Drawing Contour Maps: Drawing contour maps with a scale of 2.5 cm for 457 m to 762 m and contour intervals ranging from 3 m to 6 m.
3. Detailed Examination and Analysis: Conducting detailed examinations and analyses of the geographical formation of the soil layer in the area.
4. Proposed Tunnel Slope: Establishing the slope for the proposed tunnel.
5. Determining Permanent Stations: Establishing the permanent stations for the alignment and determining the length of the tunnel.
Setting Out Culvert:
The most effective practical method for setting out a culvert is to follow the center line of the relevant road or railway and the adjacent drain, which is considered its reference axis, with the center point located at the center of the culvert. The positions of the abutment and wing wall corners of the culvert are specified through coordinate calculation. The relevant engineer is provided with a tracing of the culvert’s foundation plan. The coordinates of the abutment and wing wall corners must be included in a tabular format on this plan.
Setting Out Bridges:
The process for setting out a bridge or bridge installation follows the same procedure as culvert installation. However, only the AOB (Above Ordinary High-Water Level) and COD (Crown of the Drain) lines are established at the corners of the road or railway and the center line of the river.
Abutment Installation: After establishing the AOB and COD lines, the corners of the abutment are accurately set using a steel tape, following the previously described procedure.
The process of Bridge Setting Out is an important activity that ensures the correct location, dimensions, and implementation of the design for bridge construction. Its main aspects are as follows:
1. Accurate Location Determination:
Positioning: Coordinates are determined for the accurate position and shape of the bridge, ensuring that it is placed according to the plan.
2. Design Implementation:
Structural Components: Various structural components of the bridge, such as piers, crossbars, and other elements, are set correctly.
3. Establishment of Reference Points:
Guideline Setup: Accurate reference points and guidelines are established on-site to maintain precision during construction.
4. Height Determination:
Accurate Elevation: Leveling instruments are used to determine the height and levels of the bridge.
5. Environmental Considerations:
Water and Geological Conditions: The location of the bridge depends on water and geological conditions, making accurate setting out essential.
6. Use of Technology:
GNSS and Theodolite: The use of modern technologies such as GNSS (Global Navigation Satellite System) and theodolites helps in determining the exact coordinates of the bridge.
7. Guidance for Engineers:
Instructions for Engineers: Accurate guidance is provided to engineers so they can complete the construction activities effectively.
8. Inspection and Verification:
Inspection: After setting out, an inspection is conducted to ensure that everything is in accordance with the plan.
Conclusion:
Bridge setting out is a complex and important process that, when carried out correctly, ensures the success of construction activities.
Bridge Survey:
For large and significant bridges, it is essential to conduct a topographic or geological survey of the selected location and the approach to the bridge. The data obtained from the survey are plotted at a scale of 1:1000, and contours are projected at intervals of 1m to 2m, depending on the nature of the land. The following detailed information is recorded in the geological survey:
- North-South alignment.
- Naming of the river and the direction of its flow.
- Names of the nearest towns at both ends of the bridge.
- Required width of the road on the bridge.
- Width of the existing access road to the bridge.
- Radius of the curves on the access road to the bridge.
- Description of the benchmark considered as the datum, its elevation, and the land height up to 150m on both sides of the upstream and downstream regions.
- Minimum water level and maximum flood level.
- Catchment area, maximum flow at the bridge, and maximum flow velocity.
- Results from trial pits, boring, and other related works.
Setting Out Piers of a Bridge:
This presents a two-fold problem, namely:
- Accurately determining the distance of the centerline of the bridge, that is, measuring the distance between a point on one bank of the river and a point on the opposite bank along the centerline of the road or railway; and
- Establishing the center point of each pier.
For short bridges, the distance or the centerline distance is typically measured using a standard steel tape. However, the steel tape must be of acceptable quality or should be compared with a calibrated tape.
In this case, the length measurement process is similar to the baseline measurement process in the triangulation method at the third stage. On the other hand, for large or long bridges, the length is usually measured through the triangulation process.
Setting out works for Setting Out Survey
Additionally, setting out survey is a plan or map preparation process for a particular area, Inaugurating with works and Inaugurating in the construction of an Innovation structure in the area. Similarly, they use all types of equipment in surveying works. Similarly, Survey work has one practical application. Furthermore, people often neglect, rushing through them in an attempt to save time. As a result, errors may occur in the work, necessitating additional time for correction. However, Consequently, construction equipment and plants remain idle, leading to an increase in construction costs.
(1) Similarly, accurate three-dimensional measurements of the structure to be Assembled ensure Accuracy in its size, plan position, and height.
(2) In the same way, once the survey process has Launched, it is essential to complete the construction work as swiftly as possible without any Disruptions
Moderator of Setting Out Surveying works
(A) Horizontal controller
(B) Vertical controller
Setting Out Survey
Furthermore, it is necessary to Instigate nearby Planar Manager stations. But also, this Planar Manager also setting out survey as indispensable reference points for Identifying the planned positions of key points in the planned structure.
Moreover, the Surveying stations represent the primary level controllers. Following these initial control points, the second-level control points are Pioneered in a similar manner
Determining the Positions of the second-level control points takes place during the traversing process. Moreover, the second-level control points offer comprehensive area control.
However, for this reason, on a construction site, it is advisable to position control points at a safe distance from the construction boundary to prevent any damage to these points during construction work at survey.
Specifically, we apply the well-known principle of working from the whole to the part to all these control points.
Vertical Controller Setting Out Survey
is a crucial aspect of surveying, particularly in construction projects, where vertical alignment and elevation play a significant role in ensuring the integrity and functionality of structures. This survey process is essential for establishing accurate vertical controls for various construction activities, such as roadworks, bridges, and buildings. Here are the key elements involved in a Vertical Controller Setting Out Survey:
1. Objectives of the Survey
- Elevation Control: To accurately determine and set vertical control points that will be used to establish the elevation of various features in the construction area.
- Consistency: To ensure that all vertical measurements are consistent with the design specifications and standards.
2. Preparation
- Design Plans Review: Review the engineering and architectural plans to understand the required elevations and any specific vertical control requirements.
- Selection of Control Points: Identify suitable locations for vertical control points based on the project’s requirements and site conditions.
3. Setting Up Equipment
- Surveying Instruments: Use precise instruments such as levels (e.g., automatic levels, digital levels) or total stations equipped with leveling capabilities to measure vertical distances.
- Calibration: Ensure that all surveying instruments are calibrated correctly to maintain accuracy in measurements.
4. Field Survey
- Establish Control Points: Using the selected equipment, establish control points at designated locations. These points will serve as references for all vertical measurements.
- Vertical Measurements: Measure the height or elevation of existing points and compare them with the designed elevations from the project plans.
- Use of Benchmarks: If available, use established benchmarks as reference points to ensure the accuracy of vertical measurements.
5. Data Recording
- Documentation: Record all measurements, including the heights of control points, any discrepancies from the design elevations, and any adjustments made.
- Observations: Note any site conditions that could affect vertical alignment, such as changes in ground elevation, obstructions, or other environmental factors.
6. Analysis and Adjustment
- Data Analysis: Analyze the recorded data to identify any inconsistencies or errors in the vertical measurements.
- Adjustments: Make necessary adjustments to ensure that the elevations are aligned with the design specifications. This may involve re-measuring or recalibrating equipment.
7. Final Verification
- Verification Survey: Conduct a final verification survey to confirm that all vertical control points and measurements meet the project’s specifications.
- Quality Control: Implement quality control measures to ensure the accuracy and reliability of the survey results.
8. Reporting
- Survey Report: Prepare a detailed report summarizing the survey findings, including the established vertical control points, measurements taken, adjustments made, and any recommendations for future work.
- Documentation Submission: Submit the report to relevant stakeholders, including engineers, project managers, and construction teams, for further action.
Conclusion
A Vertical Controller Setting Out Survey is essential for maintaining the accuracy of vertical alignments in construction projects. By establishing precise control points and carefully measuring elevations, this survey process helps ensure that structures are built according to design specifications, enhancing their safety and functionality.