# Presentation: 486874

## Detecting Bridge Scour by Thermal Variations Across the Stream Bed

***July 19, 2000***
**Presented by Paul L. Sharp**

## Problems with Current Scour Detection Technology

- The technology may be difficult or expensive to deploy
- Current technologies may be susceptible to damage in the harsh waterway environment
- Adverse conditions, such as debris accumulation, ice, suspended material, etc., may cause the device to fail

## Proposed New Approach to Scour Detection

- Use thermal sensors to detect temperature variations across the stream bed
- This approach has the potential to be less expensive and more durable than other technologies
- The Tennessee Department of Transportation sponsored  the University of Memphis to investigate this idea

## The Basic Principles of TSD are:

- The temperature of the streambed remains relatively constant (typically the average yearly temperature for the area)
- Abrupt changes in the temperature near the water-soil interface indicate exposure to surface water resulting from scour

**Notes:**
Installation Costs:
Magnetic Sliding Collar:  $3,500
Driven Rods:  $3,000 - $6,000

Equipment Costs:
Magnetic Sliding Collar: $2,500 - $4,000
Driven Rods:  $4,000 - $5,000

## Potential Disadvantages of TSD:

- In the Fall or Spring, the water temperature and the soil temperature are nearly equal at some point
- However, rainfall events usually generate flows where temperature in the channel changes
- Warmer temperatures in spring and cooler temperatures in the fall

**Notes:**
Installation Costs:
Magnetic Sliding Collar:  $3,500
Driven Rods:  $3,000 - $6,000

Equipment Costs:
Magnetic Sliding Collar: $2,500 - $4,000
Driven Rods:  $4,000 - $5,000

## Development and Testing of Prototype Device

- Thermocouples are mounted along the wall of a stainless steel tube
- The spacing gives the temperature gradient  along the tube
- The device was first tested in the lab

## Data Acquisition System 

- A computer at the site captures the data from the thermocouples
- A large steel box was used to hold and protect the computer system
- The box was attached to the bridge

## Major Advantages of Digital System

- Lower cost than analog systems
- Easier to construct than analog systems
- Develop software specific to the project
- Data storage, transmission, and analysis are simplified

**Notes:**
Get a cost comparison

## DS 1920 iButton Capsule

## DS 1920 iButton Capsule

## DS 1920 Thermal Probe

## TSD System Architecture

## TSD System Architecture

- TINITM : _T_iny _I_nter_N_et _I_nterface
- The TINITM board is JavaTM computer

- Web-enabled client
- Low Cost (less $100)
- Low Power

## Field Test Site Selection

- A suitable site was selected just outside the City of Memphis
- Telephone and power connections were available at the site
- A large scour hole was evident downstream of the bridge

## Installation at Clear Creek Site

- A pair of 50-ft. long steel piles were driven into the streambed to act as anchor points
- The thermal probe was installed by jetting into the sandy soil
- The device was bolted to the flange of the pile with clamps

## Installation at Clear Creek Site

- Data cables are exposed to debris accumulation and failure
- A pile extension was proposed to elevate the cable connection above the height of the surrounding channel banks

## Installation at Clear Creek Site

## Field Data for March 1997

## Scour Event - December, 1999

## TSD in New Bridge Construction

## TSD in New Bridge Construction

## DS 1920 Test Pile

- A water-tight modular PVC pipe system was developed to protect the DS 1920 sensors inside the pile

**Notes:**
What is 8-bit?

## DS 1920 Test Pile

- The PVC pipe system will allow for the DS 1920s to be easily  arranged into a water-tight sensor array

**Notes:**
What is 8-bit?

## Future Development

- We propose the development and installation of five additional sites in West Tennessee during the next year
- We will monitor and maintain these sites
- We will provide the data and the analysis of this data via the web
- In addition, we will develop the capability to access the data at the site in real-time

## TSD System Architecture

## TSD System Summary

- Modular and reusable
- Adaptable to wide variety of scenarios
- Provides easy access to data
- Can incorporate analysis programs
- Cost effective to develop and deploy

## Questions?