geotechnical pressure mapping

8/16/2019 Geotechnical Pressure Mapping

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PRESSURE MAPPING:

GEOTECHNICAL ENGINEERING

ACHIEVE DESIGN AND PROCESS OPTIMIZATION

WITH INTERFACE PRESSURE MEASUREMENT


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PRESSURE MAPPING: GEOTECHNICAL ENGINEERIN

TABLE OF CONTENTS

1. Why Is Interface Pressure Measurement so Important?

2. What Is a Pressure Mapping System?

3. What Are the Advantages of Using a Pressure Mapping System?

4. Geotechnical Application Overview

5. Construction Applications

6. Environmental Testing Applications

7. Geological Study Applications

8. Conclusion

O VERVIEW

Civil and geotechnical engineers and researchers must consider thebehavior of earth materials when developing designs and constructionmethods. These professionals are seeking ways to:

• Conduct soil impact and compaction tests(landslides, earthquakes, soil drainage)

• Evaluate different soil compositions and mixingmethods (Rheology)

• Test different construction methods (soil excavation/sift)

• Determine the influence of above ground activity onburied structures

• Explore the effects of seismic activity on building structures

A critical part of understanding this relationship and assessing risk isdetermining the force and pressure exerted when objects are movingor in contact.


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Even between surfaces that appear relatively flat, interface pressure

distribution is often non-uniform, with localized areas of peak

pressure. In order to locate these concentrations of peak pressure,

localized interface pressure measurement is necessary. This data

is crucial in solving many problems involving structural design and

quality, construction processes, and geotechnical studies.

The ability to match the interface of the surfaces applying the load

becomes critical as the shape of the target becomes increasingly

abnormal. Therefore, to obtain optimal data, measurement

devices should minimally impact the contact pressure profile of the

materials being measured.

1. WHY IS INTERFACE PRESSURE MEASUREMENT SO IMPORTANT?

1. WHY IS INTERFACE PRESSURE MEASUREMENT SO IMPORTANT?

2. WHAT IS A PRESSURE MAPPING S YSTEM?

Pressure Mapping Sensor

I-Scan System

2. WHAT IS A PRESSURE MAPPING S YSTEM?

A Tactile Pressure Mapping System measures interface

pressure between two surfaces, utilizing a thin and flexible

sensor. It can identify the location and magnitude of peak

pressures, or visualize pressure gradients across an interface.

The system is comprised of a sensor, data acquisition

electronics, and analysis software.

•Sensor:

Exceptionally thin-lm, exible, and highresolution pressure / force sensor array.

• Data Acquisition Electronics: Electronics scan thethousands of sensing points within each sensor. The datais instantly relayed to the software on a PC.

• Software: Displays the pressure distribution data inmultiple formats for superior analysis. Data and imageryof the pressure distribution are shown in real-time, withthe ability to record, play back, and save. The user cancreate and customize graphs from the correspondingmovie data, or export the data as an ASCII le for use withother programs.


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TECHNOLOGY COMPARISON

Below are three technologies to consider when trying to measureforce or interface pressures. While there is some overlap with theinformation each sensing technology provides, they each presenta unique value in the problem-solving process.

Load Cell

• Reliable, but no data on pressure distribution

Pressure Sensitive Film

• Flexible, but can only measure peak pressure

Tactile Pressure Sensor

• Versatile, with unique pressure distribution data

Download our white paper:

Comparison of Interface Pressure Measurement Options.

3. WHAT ARE THE ADVANTAGES OF USING A PRESSURE MAPPING S YSTEM?

• Clear visual representation of pressure distribution

• Real-time feedback of adjustments made

• Thin sensor provides minimal interference between the objects

being measured• Versatility: single analysis tool for a broad range of applications

• Sensors are customizable to specic form factors, resolutions, andpressure ranges, to meet the needs of unique applications

• Sensors are available for high temperature and humid conditions

• Software can interface with third-party analysis tools

• Offers insights to enhance product design, manufacturing, quality,and research

3. WHAT ARE THE ADVANTAGES OF USING A PRESSURE MAPPING S YSTEM?


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4. GEOTECHNICAL APPLICATIONS

This section reviews some common geotechnical applications and showsthe information that a Tactile Pressure Mapping System can provide.Pressure mapping provides geotechnical engineers with insight into thebehavior of earth materials and helps them investigate the area they areconstructing. This information allows engineers to make sound decisions

about the materials they are using to build foundations, earthworks,etc. and how those materials interact. Below are some examples ofconstruction method applications, environmental impact studies, andgeological impact studies using pressure mapping systems. Pressuremapping systems can be used in a variety of geotechnical applicationsand it is only limited to the imagination of the engineer!

CONSTRUCTION METHODS

MORTAR MIXTURE

A compression test measures the compressive strength of a material,

such as concrete or mortar mix, in a hardened state. A pressuremapping system can be used to study the rheologic properties(flow) of construction materials to evaluate different compositionsand mixing methods. This test is important when analyzing thestrength and possible weak spots of the concrete or mortar. Thegoal of the engineer is to use materials that will build a foundationwith uniform pressure resulting in a more stable structure.

Pressure Profile of Mortatr Mix



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MATERIAL SIFTING

Pressure mapping can also help to verify structural uniformity. Geogridsconsist of geosynthetic material used to reinforce structures andearth materials, such as soil and rocks. Geogrid applications includereinforcing retaining walls and subbases for roads. In the figure below,the pressure sensor (19” x 17”) sits on a foam base, with a GeoGridcovering the top half of the sensor. Five pound buckets of sand arepoured on each half, creating approximately 4” of sand cover. In thetop half of the image below (with the grid), pressure is more evenlydistributed than the bottom part of the sensor without the grid. As aresult, the Geogrid helped to evenly distribute the load and eliminatehigh pressure spots. This evaluation reinsures the benefits of geogrids,allowing civil engineers to build where it was otherwise impossible.

Pressure Profile of Sand Over Geogrid

SOIL COMPACTION

Soil compaction tests are used to understand the compaction characteristicsof different types of soils and the effect of different construction methodson nearby structures. In the image below, a sensor is placed verticallyagainst a tank wall filled with soil. Notice the pressure increases towards thepart of the sensor that is buried the deepest. In this image you can see thedifference in high pressure points (the red) before and after compaction.Thisexample provided engineers with quantitative data and a clear view of thepressure distribution before and after the soil was compacted.

Pressure Profile of Soil in a Tank



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In a similar experiment, sand was poured between 4 concrete blockswith a sensor placed vertically against one of them. The 2D view belowshows pressure profiles with a box around the key measurement area.Left: sand only; center: plus one block; right: plus two blocks. Raw forceis shown in the colored box in each window. The graph shows pressurevs. distance across sensor columns. The results show that, by addingmore blocks to further compact the sand, force and pressure againstthe measured concrete block is progressively increased.

Analysis of Sand Compaction with Concrete Blocks

FLAT JACK

Pressure mapping systems can be used in masonry to measure

the pressure exerted inside a wall. In this example, a sensor wasapplied to a flat jack to measure pressures inside a brick wall. Flat jacks are used in civil engineering when high pressures and forcesare required. These devices help to provide insight into the insideof a structure and help detect the need for structural alterations.This type of data helps engineers and builders to identify weakspots and make decisions about reconstruction, while alsogauging the life expectancy of the structure.

Pressure Profile of FlatjackInserted into Brick Wall



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ENVIRONMENTAL TESTING

SOIL COMPACT – AGRICULTURAL

Pressure mapping systems can be used to measure how different soilcompound compacts under various stresses. One use of this data is to gaininsight on how agricultural and off-road tire designs affect the soil compaction.The size, shape, tread pattern, and inflation pressure all influence this process.

This information is important because it in turn affects environmental factorslike soil drainage and absorption. The data collected by the sensor embeddedbelow the surface provides engineers with insight on which wheels are mosteffective without damaging the environment (crops, drainage systems, etc.).

Tractor Drives Over Tekscan Sensor Buried 100mm Under Soil

LUNAR E XCAVATION

Pressure mapping can also be used to optimize R&D tools. Below,a researcher uses a pressure mapping system to measure the forceaccumulation of soil on various excavator blades. The blade is fixed to astationary rod, while an open box, filled with Ottawa sand (to mimic lunar soilconditions) is moved at a constant speed to force the collection of soil on theblade’s surface. A Tekscan sensor was attached to a 12” x 2” flat model blade.

Overall Force Accumulation vs. Time for Several Tests

Tekscan Sensor Mountedon Excavator Blade



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CONTACT US TODAY FOR A DEMONSTRATION!

GEOLOGICAL IMPACT TESTING

SEISMIC ACTIVITY

Seismology is the study of earthquakes and seismic waves. Pressure mapping is a helpfultool when researching the environmental impact of earthquakes and the effect on structuresinvolved. In this example, a sensor was mounted on a backfilled vertical wall, 1:1 scale shakertable (earthquake simulation). The pressure mapping system was used to measure pressure

points when an earthquake was simulated. This data gives researchers greater knowledgeabout the pressures created by earthquakes. They can use this data to help civil engineersbuild stronger structures that can withstand these environmental pressures.

Analysis of Earthquake Simulation onPressure Sensor Mounted to Wall

5. CONCLUSION

Civil engineers, researchers, and environmentalists are looking for ways to gain more knowledge

about how earth’s materials interact and their effects on surrounding objects. Interface pressure

measurement provides a better understanding of the relationship between two objects in contact,

which can be critical to gaining a unique knowledge, resulting in better decision making. This data can

be used to help better our processes and overall well being of the earth and its materials.

Visit www.tekscan.com/pm for more information on pressure mapping technology and products.

A Tekscan Pressure Mapping System is a versatile research toolkit for geotechnical applications. Withindustry-specific sensors and software analysis tools, and high-speed, high-temperature, and wirelesscapabilities, it provides data you cannot get anywhere else.

© 2016 Tekscan Inc


5 CONCLUSION

geotechnical pressure mapping

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