Redefining Preliminary Survey in Railways

Saksham Bhutani

Saksham Bhutani , Marketing Head at Indshine

November 07, 2019

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We all have experienced delays in trains. Delay in the arrival of trains is very frustrating for passengers and often leads to missing connecting trains/flights, delayed arrival at work or some important event. Economically, delays have a negative effect on the demand for passenger and freight trains services.

There may be many reasons associated with delays, but highlighting the most frequent one - "congestion around junctions". Junctions face many too and fro activities of the passenger train and hence if not needed freight trains can be by-passed to avoid congestion in yards/ station area.

Tackling the situation, Indian Railways decided to build railway bypasses at six major railway junctions that include Sawai Madhopur, Itarsi, Guna, Ruthiyai, Jabalpur, and Ramganj Mandi Junctions in the year of 2019. "Bypass Railway Line" is also referred to as the "Chord Line". The following map highlights the location of respective junctions.

Locations of all junctions

Concept

The executive body including officers - Chief Engineer, Deputy Chief Engineer, and Executive Engineer from Indian Railways, proposes any new construction line to the upper management in Railway Board with the findings from Reconnaissance Engineering Cum Traffic (RECT) Survey. Post the same, the decision is made on whether to sanction the project or not.

Railway Board sanctions and allocates an estimated budget on the basis of RECT survey, post which Preliminary Engineering Cum Traffic Survey (PECT) and Final Location Survey (FLS) survey are executed to further proceed for construction of the proposed line. Attached report for a detailed overview of RECT, PECT and FLS Survey.

PECT Survey has five major components of the proposed three alignments :

  1. Technical Feasibility Report
  2. Land Acquisition Report
  3. Approximate Cost
  4. Existing Structures, Road over Bridges (ROBs), Road under Bridges (RUBs)
  5. Geo-technical Investigations

Scope of PECT Survey

PECT survey of "Bypass Railway Line", hereby referred to "Chord Line", has three major works which are enough for five components mentioned above :

  1. Finalizing Alignment
  2. Preparing Land Acquisition Plan
  3. Earthwork calculation for Cost Estimation

The above activities require a topography survey and the first name that comes to mind is land surveying. So, first of all, let's understand the key points which are not addressed with traditional land surveying methods.

Pain Points

Traditional land surveying techniques, including Total Station/Theodolite/Dumpy Level and Differential Global Position System (DGPS), poses the following challenges:

  1. Delay in actions because of lack of transparency: Since land surveying techniques don't have a visual component, it becomes difficult for railway officials to analyze the information. This, in turn, leads to multiple visits on sites, holding joint meetings and web conferencing to arrive at a point.
  2. Compromised decision making due to Incomplete Data: When it comes to planning, there are very tight schedules. Land surveying techniques are time-consuming and hence it's difficult to capture the smallest information. But you never know, how important can be your smallest information. Specifically, in cases of land acquisition, this smallest information can cost a million of dollars. Strange !! The lack of information, in turn, leads to a compromised decision making.
  3. Inaccurate assessment due to Manual Errors : All land surveying instruments are labor-intensive and hence are prone to manual errors. Surveying job actually requires high precision and accuracy because the results directly affect the quantities and costs. The inaccuracies of quantities maybe sometimes more than 200%, if not done properly.

yard planning

Approach

With the above pain points in mind, choosing the right approach was crucial. Aerial surveys can be very promising in planning new infrastructure if utilised properly. Drones are predominantly best in the aerial surveys. The following approach is followed :

image illustrating step by step process for aerial survey

  1. A quad-copter drone was used to fly over the entire region on the planned mission. Mission Planner application was used.
  2. A total of 8228 high-resolution images and a total of 95 ground control points (GCPs).
  3. The photogrammetry technique was used to merge and scale those images to generate an orthomosaic and digital surface model using AGISOFT Photoscan.
  4. Digital Surface Model was converted to Digital Terrain Model with the help of QGIS.
  5. Advanced tools of Indshine and Google Earth Pro were used for planning the best possible alignments.
  6. AutoCAD Civil 3D helped in creating longitudinal profile, and cross-sections along with earthwork quantity estimation report.
  7. 3D models were generated for advanced analysis of water bodies.

bim

BIM Model at Ruthiyai Bypass

Marking existing and proposed land boundaries:

  1. All the land records, existing line alignment and other data available with railways is mostly in the form of paper-based documents were collected from Open Line of Indian Railways.
  2. 7/12 (latest) Extracts and Village Maps were collected from Collecting Ready reckoner from Sub Register Office.

While designing alignment and elevation profiles in AutoCAD, following parameters were kept in mind.

  1. Embankment had a slope of 2:1
  2. Embankment width was considered as : For curve= 8.15m; For non-curve= 7.85m
  3. Berm width of 0.5m wherever the difference of Formation Level and Ground Level will go more than 6m.
  4. Retaining walls to be built wherever land acquisition is not possible.
  5. Embankment width in platform area would increase according to yard size.

Detailed codes and provisions of Indian Railways can be accessed at this RDSO document.

Longitudinal section profile for proposed Ruthiyai Railway Bypass Longitudinal profile of proposed railway alignment

Cross-sections showing cut & fill area and ground elevation profile Cross sectional profile at chainage 15000 of proposed alignment

Results

The major requirements of PECT survey being alignment planning and earthwork estimation, they arrived with following results :

Alignment Planning: Proposed bypass alignment with important structures marked along-with land boundary details.

Earthwork Estimation Report: Proposed alignment construction has the following cost implications:

  1. Fill Volume: 3,055,107.14 cubic meter
  2. Cost of Earthwork: USD 10 per cubic meter
  3. Net Estimated Earthwork Cost: USD 30 Million

Earthwork Volume Report

Summary

The change in process of PECT survey has altogether given excellent results to Indian Railways.

Manish Gupta (Deputy Chief Engineer, Bhopal) explains - PECT surveys have never been this rich in information. Drones are actually combining PECT and FLS survey saving us a hell lot of time. Indshine tool gave us the capability to work on drone maps along with my counterparts and Executive Engineers improving our day to day decision-making process.

Quickly summarizing the advantages with a new approach followed :

1. Digital Information (High-Resolution Map and Digital Surface Model) helped in reducing visits:

During finalizing alignment, in Indian Railways, it typically requires 4-5 stakeholders each from the open line (maintenance), construction, electrical lines, signal telecom. Various other organizations including the Land & Revenue department, Irrigation department, Roads and highways department, Powerlines department are involved while finalizing the land acquisition plan. Hence there are multiple stakeholders which require joint meetings and visits. The new process of the PECT survey has helped reduced visits by 10 times.

2. Accurate Data (Earthwork Volume) saved million dollars:

Traditional process - land surveying techniques involved high manual intervention and hence higher probabilities of manual errors. The new approach used drones, which are predominantly autonomous in nature. Also, the digital surface model generated from aerial surveying has elevations of the entire region and hence the volume estimation report is much more accurate. The automation process actually saved 1.2 million cubic meters equivalent to 12 million USD.


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