Ballasted Tracks 20Th May 2015

Ballasted tracks 20th May 2015

By: Mohamed Wehbi & Peter Musgrave

Track Bed Investigation Team

/ History

• First train in UK 1821

• Laying the track directly on the ground

• The importance of ballast was understood In the early 1900s

• Ballasted tracks First introduced

• Full ballasted tracks in 1930

• (After Claisee & Calla, 2005)

/ Advantages of using ballasted track

• Load distribution and provide elasticity to the system

• Track stability (lateral and longitudinal)

• Good drainage and prevent vegetation

• Facilitate maintenance and adjusting geometry

/ Disadvantages of using ballasted track

• Losing geometry after a period of time

• Limited lateral resistance

• Susceptible to contamination and slurry pluming.

• Particle flying off

/ Ballast specification overtime

100 98 98 100 50

10 10 10

British Rail (1988)

%Passing 1 1 NetworkNetwor Rail Rail (2011) 1 0.40.4

0.1 1.18 14 22.4 28 31.5 37.5 40 50 63 80 Sieve size (mm)

(After Claisee & Calla, 2005)

/ Track Maintenance

Date 00.00.00 / Maintenance Methodology

Site is flagged

Desk study

Site investigation

Diagnosis & treatment solution

Site monitoring

/ Desk study

This is a type of investigation that is carried using data from different sources:

1. Video Recording 2. Drainage condition (general) & Topology 3. Components age from maintenance records 4. Geology 5. HSTRC data & CCQs 6. GPR

/ Desk study

/ Desk study - HSTRC

The High Speed Track Recording Coach is equipped with a number of sensors that measures various parameters such as :

1. Top/vertical rail profile 2. Gauge 3. Crosslevel 4. Horizontal alignment

/ Desk study - HSTRC (CCQ)

Is representing the change in the track quality (Top, AL) in the time domain.

/ Desk study - GPR

GPR device is designed to shoot electromagnetic waves into the track to detect sudden changes in material, i.e layer interface. GPR waves are typically shot at different frequencies which provide different penetration depths and. The advantages of using GPR are:

1. It is continues and non-destructive technique. 2. It can be used to estimate ballast thickness. 3. Possible detection for wet pockets in the ballast. 4. Detecting subgrade erosion and slurry pumping.

/ Desk study - GPR

1 GHz GPR, depth of 1000mm

2 GHz GPR, depth of 500mm

Processed 2 GHz GPR, fouling index

/ SI scope

SI scope = Desk study + sites investigation outcome.

Site investigation consist of the following:

1. Visual inspection for contamination 2. ABS 3. Trial pits 4. FWD 5. Dynamic probing 6. Drainage investigation

SI scope - ABS

The ABS device is based on driving a clear sampling tube through the track between sleeper cribs to retrieve a representative sample core of the track bed compositions, up to 2m in depth

1. Determining the level of deterioration in the ballast and formation layer. 2. Indentifying ballast contamination and interface problems, slurry pumping. 3. Providing an estimate of layers’ bearing capacity and water content

/ SI scope – Trial Pits

A trial pit is a hand dogged excavation up to 1m in depth between the cribs with the potential to be extended to the shoulders. The obtained sample can be used for similar purposes as the ABS sample; however, the TP sample can be less accurate due to the reliance on labour work and may cause contamination in the track bed.

/ SI scope - FWD

It is a device that is adapted from the road industry in the UK and it is designed to drop a mass (125kN), deliver an impulse load, from a specific height on to the sleeper to excite the track. A number of sensors, geophones, measure the deflection values along the track

1. Determine the global static stiffness of the track at discrete points.

2. Determine the stiffness of different individual layers

3. Determine the critical velocity of the system.

SI scope – Dynamic Probing

. Is a penetration cone that is connected to a rod which is driven into the track by dropping a hammer. Depending on the track bed composition and

amount of penetration per drop, soil strength can roughly be estimated

/ SI scope – Drainage investigation

Checking the performance of each Catch pit (blockage, water flowing..etc)

/ SI scope – Reporting

/ Diagnosis

Track bed on UK tracks can be categorised into the following: :

1. Normal deterioration (old components)

2. Formation and drainage problems

3. Poor subgrade condition

4. Embankment instability

Example of normal deterioration

/ Example of formation & drainage problem

/ Underlying problems & embankment instability

Cant(mm) -2 0220 320 420 520 620 720 820 920 1020

-4 0

/ Example of underlying problems & embankment instability

/ Treatment solution

Depending on the outcome of the SI scope / desk study, a treatment solution can be recommended.

1. Formation treatment

2. Piling

3. Re-ballasting, re-rail, re-sleeper

4. Drainage improvement techniques

Site monitoring

After applying the treatment solution, site monitoring can be carried out using various techniques, such as:

1. Rail deflection video recording

2. HSTRC data and CCQs

3. Installing sensors

/ Site monitoring (Cant sensors)

/ Cant reading before treatment

December 3rd 2014 / 30 Cant reading after treatment

December 3rd 2014 / 31 Thank you all for listening Questions