Geomative GD-10 Geophysical Resistivity IP Imaging Instrument

GD-10 D.C. GEO-ELECTRICAL

SYSTEM

ST Geomative Co., ltd 2015.06

Content

Concept

Composition

Function

Feature

Operation

Case

ST Geomative Co., Ltd

CONCEPT

Electrical field equipotential surface Current

Current I

Time t

I0

t0 t1 Potential Difference ΔV

ΔV0

Time t t1 t0

ΔVIP(t)

T

0 1 2 3 4 5 t（s）

charge discharge

ΔV

ΔV1

ΔV2

ΔVMN

ΔV

ΔV1 ΔV2

DC RES bases on the electrical conductivity differences of Rock (ore) stones, it observes and studies underground distribution regularity of artificial electric field to survey.

BNBMANAM

k1111

2

I

Vk

Apparent resistivity ， k is polar distance constant

Induced polarization, bases on

IP effect difference of rock and

ore stones in the earth crust, it

prospects and solves the

geological problem by

observing and studying

distribution regularities of DC

(time domain) or AC (frequency

domain) induced electric field.

3. Function 6. Case 1. Concept 2. Composition 4. Feature 5. Operation


High density method, layout electrodes one time, it continues to measure automatically, it gathers VES and section method together, it’s able to gather multiple devices and polar distance together.

Electrode space

increases

current point

DC electrical method

DC electrical method devices have three classifications: electrical sounding, profile and intermediate gradient. There are also different kinds according to electrode layout way, 4-pole device is the most basic one.

High density method

CONCEPT

Intermediate gradient device

Dipole device Wenner or Schlumberger

Dipole-dipole device Three-pole device



Accessories

Function button

• Up-down page

• Menu

• Return

Snob，rolling menu，press

for select

Short cut key F1 F2 F3 F4

LCD screen

• 480*272

• Full color

• High light

Solid non polarization electrode

Star electrode

BP-145 DC power source The platform of design

and data management.

SYSTEM COMPOSITION

Mainframe

Intelligent cable Geomative Studio software

3. Function 6. Case 2. Composition 4. Feature 5. Operation 1. Concept


SYSTEM COMPOSITION - Intelligent cable

Compact size, light weight, convenient preparation and handling Construction wiring easy, convenient, fast and improves wiring efficiency Reliable and durable, low fault rate in the wild, the long-term use of low cost

Each cable contains 12 taps,taps the P1 and P2 connectors include 2 separate; Each P1 and P2 can be used alone, can also carry large current in parallel, or as the transmitting and receiving circuits, respectively.

Used plastic injection molding process, waterproof performance can be adapted to various applications; Simple structure, no electrical parts, high reliability, low replacement cost. 10 m spacing: 10 Kg 5 m spacing: 6 Kg

Intelligent bi-directional cable head, integrated control and switching circuits, focused two way control after two cables; As core components of the density test using aluminum alloy shell sealing design of high reliability and long life; Seal rating IP66; 1Kg.

Self-locking plug, you can quickly swap and automatic locking, easy and reliable.


For imaging survey, it needs to cover the entire length of the cable cross section, cables and switching equipment to constriction operations have a very significant impact in the field.

Special winding frame addition to the retractable cable, and can also be built into cable ends, not only improving the compactness of the unit components, but also protect the cable and cable end.


GD-10 BTSK AGI ABEM

60 channel

64Kg 74Kg 100Kg 100Kg

120 channel

119Kg 167Kg 174Kg 150Kg

180 channel

173Kg 260Kg 248Kg 232Kg

240 channel

228Kg ＞400Kg 332Kg 282Kg

SYSTEM COMPOSITION - Intelligent cable

Advantage： simple principle, low cost cable, high reliability

Centralized method

Disadvantage： Need a lot of jumper cable for long section measurement; can’t take solid non-polarization electrode for IP survey 。

Advantage： Simple layout, suitable for long section

Distributed method

Disadvantage： The structure of intelligent cable is complicate with a high cost. Any failure on one take-out will result in the effectiveness of the whole cable

Combined the advantages of centralized and distributed method:

Cables and cable head separated, individual maintenance or replacement is available; Low cost and easy to replace broken cable, cable head with a long life; Unique exchange program to enhance the compactness, reduced weight.

GD-10

Weight Compare



SYSTEM COMPOSITION - Intelligent cable layout

General Res test mode

Max current: 2A

Double-Res test mode

Max current: 4A

General IP test mode

Double-IP test mode

Max current: 4A Max current: 4A

Two sets of cables in parallel, tap corresponds to one by one, each electrode position formed by two taps and four joints;

Every joint independently assigned for transmitting or receiving electrodes are very flexible.


Cable joints and cable connected to the first, and to either sider or any side of infinity

Host automatically detect cable leader state and define the location

Select the cables and electrodes arrangement styles

Testing grounding resistance detection electrode connection


SYSTEM COMPOSITION - power source

Built-in battery

• Battery capacity: 7.8mAH

• Working voltage: 11.1V

• Charge voltage: 100~250V @50/60Hz

When the built-in battery is exhausted, or you can use any DC power supply output voltages in the range of 5~70V

• Specially configured for portable external power supply

• Car cigarette lighter power supply

• Car battery 12/24V

• BP-145 batteries 48V * In the wild for a long time operation of the system

• BP-145 intelligent control of power supply, you can choose 48V,96V or 144V output;

• While three series, superimposed voltage of 450V, with 2 a output current, up to 900W power.

• Using the generator and rectifier combination of source, you can further increase the transmit power until full launch.

Working Power Transmitting Power



SYSTEM COMPOSITION -Software

Simplify input

Indoor Define project Define survey area

The wild New task: Select project survey area

Extensive testing to classify objects management

For later data

modeling

For measuring task in the region /Data merge.

Device management

Engineering/data management Script management

The platform of Geomative devices

Managing test data Manage Task script

Manage GD-10 device

Geomative Studio


Project

Survey Area

Tasks/Data

1D Script

2D Script

3D Script

Set parameters

Upgrade software

Through the device management to continue the Geomative Studio and the GD-10 firmware upgrade.


FUNCTION - 1D VES

Dipole Device

Intermediate gradient device

4 pole vertical sounding Measuring data scatter diagram

• Repeated measure on one

point

• Discrete degree react the test

conformance

• Discover bad point to ensure

the reliable data

Upgrade by

online software,

it will support

more arrays in

future.

6. Case 1. Concept 2. Composition 4. Feature 5. Operation

3 pole vertical sounding

1D IP sounding

1D Res sounding Full power(1200V*6A) launched in support of high-power induced polarization tests;

Support up to 100 iterations, improve test accuracy;

In addition to custom arrays, you can script, enter four device in advance of running parameters

3. Function


FUNCTION – 2D Res/IP Imaging

Six generic appliances：

Wenner α Wenner β Wenner γ Three-pole direct array (δA array) Three-pole reverse array (δB array) Schlumberger *Scalable, supports more devices * Customizable installations



FUNCTION - 3D Res/IP Imaging


Three commonly devices: pole-pole, pole-dipole and dipole-dipole;

Devices of 2D and 3D are interchangeable;

Device is customizable.


Function - The Programmable Script

2D script 3D script

Supports a variety of generic device type, when a device is selected, based on number of devices and electrodes automatically generate a complete sequence of measuring points;

Point-by-point or layer with the specified number of iterations, for shallow strong signal without iterations to quickly measure to improve efficiency; deep on weaker signals, through several iterations to enhance testing accuracy. Both efficiency and accuracy. You can use Excel to edit the point sequence table and import to implement a custom device.

Adjust the measuring sequence, increasing the intervals between adjacent test point, thus reducing interference between adjacent points of.


Set the filter conditions, combined with the selected layer, or click the mouse, delineating testing targets, test to skip meaningless points, only for the test points of the garget area, so as to inform and improve testing efficiency.


FUNCTION - Rolling Measurement

1 2 3 4 5 2 3 4 5 6

Measuring the initial section;

Rolling cable laying;

Establish a rolling section ;

Replication the script;

Measuring the rolling surface.

* Repeat the above steps until you have completed the entire cross section measurements.

Apply to 2D and 3D tests;

Limited cable length corss-section measurement;

Long section completed;

Measuring point is not repeated, extremely high efficiency.

*Fix long plagued section survey

Rolling measurement

Measurement procedures consistent with 2D scrolling;

Only along the y direction (perpendicular to the cable extension direction) scrolling;

Scroll step size is not limited to a multiple of 12 (not every time you move through a cable).

2D rolling measurement

3D Rolling Measurement


FUNCTION - IP central gradient array section

Emitter A, B pick up ordinary cables, fixed;

Receiving m, n high density cable, serpentine routing, and automatic switch;

Cabling, completing a cross section measurements;

Constantly extending outwards, A and B, until you have completed the entire scan to work.

Current curve Decay curve Data list


High-power IP scans of the original function, set via scripting, can greatly improve the efficiency of scan.


FUNCTION - real-time monitor environment

RS485

Programmable Logic Controller （PLC）

Level Pressure Flow Temperature Analysis Location Other Onsite Sensor

GD-10

• Underground pollutant change detection

• Seawater Intrusion Detection

• Dam Detection

• Underground tank leak detection

• Slope failure detection

• Real time monitor the test condition;

• Real time analyze the data;

• Form report ;

• Issue a warning

• GD-10 supports Modbus protocol；

• The standard modular PLC ，apply for the different requirement.

Internet


Monitoring Station Gathering Station The Field Monitoring


FUNCTION - Self-potential method and rock sample measure


Self-potential method Rock sample measure

M1

M2

M3

M4 … …

geologic body

Basic line

Ⅰ

Ⅱ

Ⅲ

Ⅳ

Ⅴ

N A B M N Rock core

clay clay

insulating mat

Spontaneous electric field method based on field observation method can be divided into two by potentiometric method and gradient, potentiometric method is used more generally, current in the industry tour only noise when the gradient observed. * Used for logging and monitoring No emission source The construction is simple, high efficiency Data tampering Since m-potentiometric method MN-gradient method

Determination of parameters of rock samples Collection of geology, stratigraphic information, and providing

a basis for resistivity method. Exposed in outcrop method the natural or artificial outcrops of rock with a small scale the Schlumberger unit determination or three-pole apparatus. Specimen method as shown in the figure. Power supply electrode is inserted in the outer end of the clay core principle power, plug the measuring electrodes measure data the clay close to the core. Analysis – the analysis of the survey area has information, to know the formation resistivity.


FUNCTION - survey on water& cross-hole survey

Super waterproof (protection grade IP68 cable joints and cable), to ensure measurement of water environment on GD-10 can easily cope with. Surface testing security and stability; Automatic and continuous measurement; Built-in GPS, coordinates the record host, automatically save the data. Delineation of freshwater and saltwater interface

Probe point closer to the goal, abnormal signal is a direct reflection of the;

Transmission path simply signal fidelity and improves the signal to noise ratio, more accurate data.

Construction costs are high, step is more complex.

Dam seepage areas, widely used in cave, GoB, isolation, barriers, and the fracture zone, exploration of both high.

Underwater karst pits Looking for alluvial deposits Delineation of dissolved

limestone district

Underwater geological mapping

Crack/fault

Survey on water Cross-hole survey


In each of the two holes drilled into put a certain number of electrodes, through multi-core cable is connected the ground, between the two electrodes forming hole electrode array. Data acquisition and first electrode parity group power supply electrode (AB) odd couple pairing combined power supply, the remaining electrode measuring electrode(MB) total measurement


FUNCTION - Grounding R test

The measuring electrode

Electrode ground well, is used to test the quality and reliability of data one of the most important, so each pole,

grounding resistance test is needed. GD-10 in addition to

providing a variety of test methods and electrode

grounding resistance data integrity preservation, and as

part of the test results.

One dimensional electric sounding tests, support manual for A/B/M/N four electrodes for grounding resistance test. That is next to the GD-10 setting and m reference electrode Terminal, and then manually A/B/M/N four electrodes respectively, n-Terminal and testing the grounding resistance.

2D and 3D high density tests, GD-10 supports automatic continuous grounding resistance test, use cable head flexible and powerful switching capability, swap the electrode to be measured as n pole when connected, all other electrode swap connections at the same time as m (that is, reference electrode). Compared to the conventional method of using an electrode as reference electrode, this method is more accurate and objective.

Test Method（auto, continuously） The test scenario

Rg test for all electrodes to find the grounding resistance

It can Rg test for all electrodes connected in the long section after layout

Rg test for all the electrodes connected to the particular cable

Rg test can be done for single cable&other

consecutive cables connected in the long

section(relayed by cable leader)

Provision to set the standard Rg value(according to terrain

grounding conditions). It is arbitrary to assign any value for Rg.

After testing all electrodes. It will show the faulty electrode or electrode with bad contact

to the ground.

Rg test can be conducted for any single electrode in random fashion.

You can test the particular faulty electrode after bringing proper contact of poor electrodes.



Star electrode Simple electrode

Length 380mm 300mm

Weight 0.35Kg 0.3Kg

Materials Stainless steel Stainless steel

Grounding area 300cm2 88cm2

Rg（dry ground） 325Ω 427Ω

Rg（wet ground） 313Ω 414Ω

Rg（Saline ground） 56Ω 127Ω

Lower grounding resistance is the most effective way to enhance

the ground area of the electrodes, new design plum blossom-

shaped cross-section, reducing weight and increasing the ground

surface area, effectively reduce the grounding resistance.

FUNCTION - Star electrode for decrease Grounding R


FEATURE


For the test

For the user

For the

filed

Underground Well, hole Water surface Ground

Test method

Method Script control

Environmental

trigger

Program timing

trigger

Remote

manual trigger

Onsite manual

trigger 1D 2D 3D

IP centr

al gradient

rolling

Apparent resistivity

Induced polarizati

on

Self-potential

• Improve efficiency, reduce cost

• Lightweight and compatible

• Reliable, few failure, backup device ensure the project schedule.

• Data is accurate, objective, comprehensive, which is the fundament.

• Full function for any method.

• Test procession is visible for any problem immediately.

• Professional equipment, simple and easy operation

• Low maintenance for long-term use

• Pay as Grow， the equipment investment can be synchronized with the development of business.


FEATURE - high specifications, multi-parameters

0

U

t 0

U

t 0

U

t

1D RES/IP Sounding 2D/3D Imaging

Max voltage 1200V（P-P 2400V） 800V（P-P 1600V）

Max current 6A 4A

Max power 7200W 3200W

Technical Specifications Measuring Parameters


Receiver： Voltage range ±24V

Voltage precision 0.05%

SP compensation ±10V

Suppression of power frequency

≥95dB, 50 or 60Hz (optional)

Res survey Customized wave IP survey

Impulse (optional): 0.125s, 0.25s, 0.5s, 1s, 2s, 4s, 8s, 16s, 32s, 64s

• Include all important parameters

• Add environment parameters

• Reconfigurable parameters

IP method

Current：Ip

Potential：Vp

Pseudo R：V/I

Apparent R ：R0

Distance constant：K

Self-potential：SP

M0~M4 time window

Save the whole decay curve

Environment parameters

Latitude

Test Time

Ground resistance

Temperature and humidity

Weather

Late recalculated

Half decay：Th

Attenuation：D

Deviation：R

Integrated parameters：Zp

Res method

Current：Ip

Potential：Vp

Pseudo R：V/I

Apparent R ：R0

Distance constant：K

Self-potential：SP


FEATURE – apply for different field exploration

7 protective measures

GD-10 Mainframe

Operation Temperature： -10℃~+50℃

Storage Temperature： -20℃~+60℃

Operation Humidity： 95%

Protection： IP65

Vibration and fall protection : shock

proof rubber ring


Seal

Over voltage

Inversed grafting

Lighting strike

Leakage

High temperature

Over current short circuit

Apply to different environments


FEATURE - Software upgrade, share global experience

Software upgrade

Software system (including Geomative and GD-10 Studio software platform firmware) can enjoy free lifetime upgrade online.

* Shared global experience with the world.

User problems found during use;

Through communication and user feedback information;

Development team based on the feedback of information to improve and optimize software systems;

Through the device management software systems are upgraded.

Through user dialogues and research teams, software system has been optimized and the instrument easier.



FEATURE - No waste, low cost

Upgraded system for high configuration

Purchase in low configuration, upgrade locally, avoid tax

Modular design hardware/License/software separately

Free backup model (only for specific area)

No waste, low cost in hardware

2D to 3D+ vision could improve high power IP function.

VES

SP SP

300W 0.25% ,0.25%

2400W 0.2% , 0.1%

3200W

0.1% , 0.05%

3200W

0.2% , 0.1%

3200W

0.2% , 0.1%

3200W

0.2% , 0.1%

3200W

0.2% , 0.1%

VES

SP

IP

2D RES

2D IP

3D RES

3D IP

VES

SP

IP

2D RES

3D RES

VES

SP

IP

2D RES 2D RES

VES

SP

IP IP

VES VES

VES

SP

IP

2D RES

2D IP 2D IP

VES

SP

IP

2D RES

2D IP



OPERATION

• Intuitive

and clear • Convenient

and efficient

• Extended • Fully prepared

Edit script

Define project

Define measuring

area

More processing

Inverse modeling

Data pre processing

Evaluation of quality

Data browsing

Data collection

Layout, turn on

The new task

Start the test

Internet

In door

In field

www.geomative.com

• Authentication, active, upgrade License;

• Collect application suggestions and defect feedback ;

• Release new version, Provide online support.

GD-10

• Parameter setting is simple and rapid; • Data browse is convenient and visual; • Equipment state self-inspect, record.


http://www.geomative.com/


OPERATION - In door

Define the script – in accordance with the construction plan, established the appropriate run program. Script includes a one-dimensional script and two-dimensional and three-dimensional scripts.

When you define a script, you can select the electrode assembly electrode and measurement delineated areas, specifies the number of iterations, and so on. Free and efficient testing.

synchronization

Download the new

project and script file

to GD-10 through

USB or Bluetooth.

Define the project –Make plan to build

project, and record the basic information of

project before test.

Define the measuring area –To set different

measuring area in project management

Define project/measuring area Define Script


1D 2D

3D


OPERATION -Before test

1D 2D

3D

Environmental testing: start – cable head roll call – measurement Rg, quickly completed;

Fast wiring: cable system connected to the closure, at winder's help, efficiency has been greatly increased;

New task: whether it's a new dimension, two dimensional or three dimensional task, simply select and enter parameters

Cable Leader Track

Measure Rg

Turn On

New Test Layout

Simple, Fast



OPERATION - In test

1D Sounding Test 2D Imaging Test 3D Imaging Test


1D sounding list, select a dimension for measurement tasks;

Enter task data detail; Select measurement points, press "F4

– measure" measuring the point; The rotary knob, switch to the next

point to continue to measure. * Continuous press F4 to repeat the measurement the current point

In a two-dimensional cross section list, select two dimensional measurement tasks;

Enter task data detail; Press the "Menu" menu; In the menu select the measuring

mode. * Press "back" you can pause the current test

In three-dimension select three dimensional test tasks in the task list;

Enter task data detail; Press the "Menu" menu; In the menu select the measuring

mode. * Press "back" you can pause the current test.


OPERATION - Real-time data estimate

Real-time data estimate


VES Curves For a one-dimensional measurement is the sounding point as a whole reflected. Corresponds to the relevant model to determine formation.

Proposed Section For two-dimensional cross section measurement. Measurement can be carried out directly into this page, real time monitoring data. Compared to the right corner of the data details, directly reflect the measurement data.

Voltage Curve

The plotted values of voltage depicts the curves which reflect the real state of the current receiving channel such as frequency, interference, signal strength etc.

Current Curves

Current point of pristine current curves can reflect the true state of current transmission channel.

IP Decay Curve

Induced polarization measurements, current-excited electron reflection phenomenon. While browsing Windows and each window of the corresponding parameter values.

2D data profile

It shows all the measuring points of current survey. The bad point could be retested directly.


OPERATION - Processing

Input terrain file;

Exporting to DAT format, processed for RES software;

Export to EXCEL format, you can edit and manipulate the data in EXCEL.

Data is presented in the form of raw data and graphs;

Besides the measurement data, you can browse assigned task , properties, environmental parameters such as grounding resistance for each electrode, wind, temperature, GPS co-ordinates etc;

You can also edit the parameters, such as adjusting the IP window, water parameters are calculated.

GD-10 is enabled with USB cable to download the measured data from device to the Geomative Studio Software installed in your PC or Laptop.

Hence, Downloaded data will be default stored in the Geomative Studio Database.

Synchronization Browse Download



CASE

Resources Exploration • Underground

water • Mineral resources

Engineering Exploration Condition • Cave exploration • Pile foundation

Environment Detection

• Slope detection • Seawater intrusion • the groundwater

pollution in the landfill

Others • Geological mapping • Archaeology • Drilling/cross hole

detection



Case Study Groundwater Exploration

60 electrodes

10m spacing

Wenner Array

Both ERI array configurations show consistent geologic features with elucidation of a pair of lenticular channel bodies within the Mehrten formation volcaniclastic horizons, located at depths between 100-240 feet deep, which correspond well to the electric log for Test Well #1, located to the left as indicated. The Mehrten Formation channel located to the southeast (right) side of the image on both arrays has apparent resistivity values approaching 100 ohm-meter near its core, which is consistent with a sandy gravel filled channel. Such gravel bearing channels in the Mehrten Formation tend to have the highest ground water yields and a proposed test well is located in the channel axis as indicated at electrode station #41.

The bottom image is a

Terraserver aerial photo of

the site from Aug 15, 1998,

showing the location of

the ERI transect 1-2 and

the test well and proposed

new well location。

Both ERI array configurations show consistent geologic features with elucidation of a sandstone layer within the Mehrten Formation, located at depths between 100-220 feed deep, located on the east(right) side of the profiles. The Mehrten channel sandstone imaged on the profiles has apparent resistivity values between 45-90 ohm-meter (dart green to orange) consistent with a sandstone. A "low resistivity anomaly" caused by groundwater in fractures, bisects the channel between electrode stations 41-43 (between vertical blue lines) and corresponds to a joint fracture zone located within Dry Creek (heavy yellow line on aerial photo).

Proposed Test Well

Proposed Test Well #3

Proposed Test Well #4

Proposed Test Well #4 60 electrodes

10m spacing

Dipole-Dipole


Case Study Tunnel Erosion

Tunnel erosion, also known as “Piping”, is the subsurface erosion of

soil by percolating waters to produce pipe-like conduits below

ground especially in non-lithified earth materials. This is a type of

mechanical soil movement where by fine subsurface sediment

moves in underground channel ways through permeable materials.

Interpretation for the ERT Imaging :The length of the survey line was 60mts ,with 1m electrode spacing ,totally 60 electrodes are involved. These distorted layers impregnated with

freshwater are delineated from 5m to 10m depths. The low resistivity that ranging from 100 to 130 Ohm M at the depth of the 6m on either sides of vertical structure in the profile implies

the presence ‘ sand pipes’ in the study area. These low resistivity layers are engulfed by the freshwater zone with a range of resistivity values from 35 to 122 Ohm M below 6m from the

surface. The high resistivity zone of base rock is identified with 1581 to 2577 Ohm M at a depth of 236m. The low resistivity zone of circled image indica tes the path of the ‘pipe’ like

structures which clearly depict the resistivity value that ranges from 536 to 786 Ohm M.

60 electrodes

1m spacing

Wenner Array


Case Study Hydro-Carbon Contamination Study

Hydro Carbon Contamination Study:Electrical resistivity surveys have been used for many decades in hydro geological, mining and Geo-technical investigations. Considering the difficulty of imaging a resistive target in a complex geological framework an integrated approach is probably best. Godio and Morelli (1999) used a conductivity meter for reconnaissance with which to plan the GPR survey. GPR was then used and followed up with an electrical resistance tomography (ERT) survey to detect and define the lateral distribution of the hydrocarbon pollution.

Interpretation for the ERT Line I :This profile runs along East -West direction which is shown in Google map.. The lithological section can be interpreted as four layer model. There are low resistivity contours up to the 1m depth from the surface in the top part of the profile indicating the presence of saturated silty sand with cobbles and pebbles. High resistivity contour suggests the presence of medium to fine unsaturated silty sand up to the 4 m depth. Saturated Oil sands generally have low resistive value than the alluvium and some of the value is overlapped between the two. The slightly low resistive value of 100- 300Ω suggest the presence of the alluvium of fine to silty sand with oil spill on the sands upto depth of around 9m. Most of the oil seepage is visible at chainage 16m and around 32 to37m. The low resistive region with contour 10-100 Ω suggest the presence of the ground water aquifer. The contrast in the resistivity of the sand at third and fourth layer.

Interpretation for the ERT Line II : This profile runs along East West direction which is shown in Google map.The lithological section can be interpreted as four layer model. There are low resistivity contours up to the 1m depth from the surface in the top part of the profile indicating the presence of saturated silty sand with cobbles and pebbles. High resistivity contour suggests the presence of medium to fine unsaturated silty sand up to the 4.5 m depth. Saturated Oil sands generally.

60 electrodes

1m spacing

Wenner Array


Case Study Quartz reef investigation

Quartz reef is used for several applications in indusial purpose. 2D Electrical Resistivity Imaging (ERI) investigation is suitable method to determine the geotechnical problems and it is used for estimation of the high quality of quartz reef bed thickness. 2D Electrical Resistivity Imaging with Wenner array was conducted within the Quartz reef area in Varasanadu, Theni district, Tamilnadu. The geology of the study area contains red soil, quartz reef and weathered gneissic rock which signify good target for 2D electrical resistivity imaging techniques. The interpretation of the resistivity data along the profile shows the model of resistivity pseudo-section in quartz reef area. The highly resistivity zone range from 103 – 407 ohm.m at a depth of 4.06 m to 5.96m indicating the presence of hard quartz reef rock.

Interpretation for the ERT Line I : The profile trends NW-SE direction to a length of 120 m. The upper part of the layer reveal as Quart reef deposits. The inversion resistivity values for these bed rock that ranges from 201 ohm.m to 27630 ohm.m.The resistivity values for intermediate layer of weathered Quart reef ranges from 28- 73.2 ohm.m. The lower part of the layer represents weathered composite gneiss with freshwater indicates low resistivity . values that ranges from 0.6979 to 11.3 ohm.m indicates alluvium deposit [1] due to the palaeo river channel; measuring a series of constant separation traverse with the increase of electrode spacing with each successive traverse. Quartz reef deposits in granulitic terrain at Varasanadu .

Interpretation for the ERT Line II :The profile (Fig.6) is trends to a length of 120m. The inversion displays the ranges by resistivity values from 7.45 Ohm.m . to 27.4 Ohm.m indicating that weathered soil up to a depth of 6m. The intermediate second layer exhibits resistivity values that ranges from 41.4 ohm.m to 130 ohm.m represents the weathered Quartz reef reef. The high resistivity zone of pseudosection with range of resistivity is 200 to 10000 ohm.m at a depth 21.5m indicating the quartz reef rock intrusion in the granulitic terrain .

ERT Line I ERT Line II

30 electrodes

10m spacing

Wenner –Schlumberge rArray


Case Study Sub-Soil ‘Foundation Study’

The Bridge Foundation Study focused on mapping vertical variations of electrical resistivity to enable detection various layers with different lithology in the subsurface at the abutment locations. The objectives of the survey are as the following: To establish 2D Electrical Resistivity sections of the ground profile showing different layers of overburden and bedrock .To find out weak zones and water bearing zones in the specified survey areas

Interpretation for the ERT Line I : This profile runs parallel to Kaligandaki River in its right bank. The 2D ERT result up to 45 m depth and respective lithology are shown in ERT I. The position of proposed abutment is also shown in the same Figure. The ERT result is discussed below. There are low to medium resistivity contours in the top part of the profile near chainage 80m, abutment location and near chainage 250m in the upstream part (marked by “a”). It indicates presence of overburden composed of alluviums with more gravels and boulders. Second layer is marked by low resistivity contours (marked by “b”) near chainages 80m. 150m (near abutment) and 250m. The low resistivity suggests presence of alluvial deposit with more saturated sands in these locations. These alluvial layers together extend to about 30m depth near chainage 80m, 12m near abutment site and 8m near chainage 250m. Near chainage 125m (20m downstream of present abutment site) the alluvial layer has mainly gravel boulder and extend only to about 9m depth. The underlying layer is marked by medium to high resistivity contours. This is may be layer with more gravels and boulders or weathered bedrock.

Interpretation for the ERT Line II : This profile runs parallel to Kaligandki river in its left bank. The centre of profile is at the proposed abutment site. The ERT profile layout is shown in ERT II. There are medium resistivity contours in the top layer from chainage 80m to 180m, including proposed abutment site. The medium resistivity suggests presence of gravel boulder layer. It extends to about 7m depth from ground surface. The low resistivity contours are present near chainages 50m, 80m to 180m and 240m. These are the zones with dominantly saturated sands. This zone extends to about 24m depth near the proposed abutment site and 9m depth near chainage 250m. The underlying layer is represented by higher resistivity contours. This may be hard bedrock layer, which may extend from 20m depth to well over 45m depth. However, at locations near chainages70m (previously drilled location) and 200m the bedrock may extend from a depth of 6m to over 45m depth.

60 electrodes

5m spacing

Wenner Array


Case Study Prediction & Control of Landslides

Landslip Study: The aim of the study is to attempt the landslide prone zone in the, Ooty region, Tamilnadu, India. The survey was carried out using GD-10 Series, multi-core cables & electrodes. Survey is assigned with Wenner configuration. The aim of the survey is to identify the landslide prone zone .The study reveals that the investigation area is highly vulnerable to landslide which is evident from the low and high resistivity zone noticed in the study area. The water body with loose sand is identified from low resistivity value, highly weathered zone indicates the presence of charnockite and compact charnokite gives high resistivity value in the study

Interpretation for the ERT Line I :The Elevation variation in pseudo-section ranges from 1060m to 1100m. The Top layer constitutes Lateritic soil with resistivity ranges from 49.4 ohm m to 68.8 ohm m. The Intermediate layer of Weathered zone of Charnockite rocks with resistivity ranges from 128 ohm m to 902 ohm .The bottom layer with resistivity ranges from 902 ohm m to 5010 ohm m, indicates the presence of Garnetiferous Charnockite.

Interpretation for the ERT Line II :In the second profile , the pseudo-section denotes that the top layer is covered by Mud with highly weathered soil in a width of 125m and in depth of 10m, the resistivity ranges from 12 ohm m to 53.9 ohm m. The Intermediate layer of weathered zone with resistivity ranges from 73.9 ohm m to 112 ohm m .The hard and compact garnetiferous rock shows the high resistivity ranges from 235ohm m to 1040 ohm m.

ERT Line I ERT Line III

Interpretation for the ERT Line III :In the Third profile ,shows the Elevation variation in pseudo-section ranges from 1078m to 1058m .The Top layer constitute Lateritic soil with high saturation of water ,with resistivity ranges from 12 ohm m to 24.8 ohm m. The bottom layer with resistivity ranges from 25.2 ohm m to 106 ohm m, indicates the presence of Garnetiferous Charnockite .

ERT Line II

30 electrodes

5m spacing

Wenner -SchlumbergerArray


The objective of this study is to generate subsurface profiles at shallow bedrock region using integrated site investigation testing. In this study drilling of borehole with SPT N value measurement, seismic testing of MASW and Electrical Resistivity Tomography (ERT) has been carried out at selected locations in Hampi, Karnataka, India. SPT gives soil type and density, MASW gives shear wave velocity and resistivity testing gives layer thickness. Integrated subsurface profiles are generated and are used to understand variation of subsurface layers in shallow bedrock sites and validate 1-D site response study assumptions. These subsurface profiles may be further used to understand difference of 1-D and 2-D site response.

Interpretation for the ERT Line I & II

Typical 2D subsurface profiles generated by combining the three methods ie, ERT,SPT and MASW

60 electrodes

1m spacing

Wenner Array

An Integrated Site investigation of shallow bedrock sites using seismic response study

Case Study

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