Zetica - e-news
September 2005 Volume 2, Number 4

In this issue

 

Useful Links:

Solution matrix for road or motorway applications
The US Federal Highways Dept has published a very useful matrix of geophysical and NDT methods for solving engineering problems during SI, construction and maintenance of road infrastructure.

WW2 bomb risk maps
Download risk maps for your region (28 regions across the UK)
WW2 bomb risk maps image

UXO frequently asked questions
Download a list of FAQ demystifying various aspects of unexploded ordnance

One-stop shop mapping service – why outsource to 3 companies when Zetica does it all?

The cost savings in outsourcing all site mapping services to one company can be considerable. Zetica offers in-house specialist desktop studies, detailed topographic surveys, Landsweep™ geophysical surveys, detailed utility surveys and engineering geophysical surveys. Our multifunction crews are trained to carry out all site-works thus saving on mobilising separate teams.

Close partnerships with Norwest Holst (drilling) and Lankelma (CPT) also means we can manage most site investigation works that may be required under one contract.

Click here to request more information on our mapping and site investigation services or visit our website www.zetica.com.

Landsweep™ survey – mapping buried tanks, and utility apparatus

The objective of the survey was to determine the location and depth of a number of underground storage tanks (UST’s) and utility apparatus.

Combined results of the magnetic profiling, time domain EM (TDEM) and ground penetrating radar (GPR) surveys confirmed the existence of UST’s at two locations within the site boundary. The precise location of the UST’s was determined primarily using the GPR data. The diameters of the tanks are estimated at between 1300mm and 1500mm. This range is based on the width of the observed hyperbolic anomalies in the GPR data and from the results of forward modelling of the magnetic data.

The summary interpretation CAD plan also shows features that were traced during a Radio Frequency Location (RFL) survey, information from visual inspection survey of the drainage chambers, apparatus identified on statutory undertakers’ plans and features identified from the geophysical survey.

Extract from a CAD drawing summarising buried structures and utility apparatus mapped using Landsweep™. Measured versus modelled magnetic field response from UST’s. GPR radargram over UST’s
Extract from a CAD drawing (left) summarising buried structures and utility apparatus mapped using Landsweep™. Measured versus modelled magnetic field response from UST’s (right top and right centre). GPR radargram over UST’s (right bottom)

Click here to email us with details of one of your sites that could benefit from a Landsweep™ survey.

Capital Towers, Kuwait – seismic crosshole measurements

Zetica was commissioned to undertake a borehole seismic survey on the site of the proposed Capital Towers building in Kuwait City, Kuwait as part of a wider ground investigation for the building. The aim of the geophysical survey was to determine compression and horizontal shear wave velocities and dynamic moduli for the geological strata beneath the site.

The survey included compression (P wave) and shear-wave (SH/SV wave) downhole and crosshole testing in a set of three in-line boreholes together with a P wave crosshole tomography survey.

Example of a receiver gather from the P wave crosshole survey illustrating reduced signal-to-noise ratio from surface to 10 – 12m depth due to signal attenuation. The receiver depth was 33m. Emax and Gmax depth profiles.
Example of a receiver gather (left) from the P wave crosshole survey illustrating reduced signal-to-noise ratio from surface to 10 – 12m depth due to signal attenuation. The receiver depth was 33m. Emax and Gmax depth profiles (right)

The most significant result of the survey is the identification of a well-defined change in the shear strength profile of the strata at a depth of approximately 30m beneath the site. Above this depth Poisson’s Ratio, Young’s Modulus and the Shear Modulus undergo a gradual increase from surface downwards, reflecting an increase in the SV wave velocity and indicating an increase in the shear strength and competency of the sands and gravels of the Upper Dibdibba Formation.

Click here to request more information on measurements of geotechnical properties of foundation materials.

UXO - detection ranges for EOC equipment

At a recent CIRIA conference in London on industry procedures for mitigating the risk of unexploded ordnance (UXO) including unexploded bombs (UXB), the lack of a standard approach to detecting UXO was bemoaned by several consultants on the day.

Zetica has led from the front (see March newsletter) in improving technical standards of service offered in the UXO risk management business. Even so, a recent project with which the company was involved at the tender stages is a shocking reminder of the problems still inherent in the industry.

The main risk identified on a site was thought to be from unexploded aerial-delivered bombs of approximately 10kg as well as other smaller calibre unexploded ordnance related to the site’s history and military activity. The client had issued a specification to detect these UXO to depths of up to 6m below ground level. A well known EOC firm recommended a solution to this problem using standard military issue detection equipment from the surface. Zetica highlighted the shortcomings of this approach and a call to the manufacturers of the equipment, who provided official detection ranges, resulted in a table of detection being issued to the customer to provide unequivocal evidence of the limitations of the equipment actually being utilised. This table is reproduced below for our readers’ benefit.

 

Detectors

 

Type 1

Type 2

Type 3

UXO type

Detection depths (m)

German Bombs:

SC-50 (50kg)

1.5

1.5

0.8

SC-250 (250kg)

4-5

3

1

SC-500 (500kg)

5

3.5

1

SC-1000 (1000kg)

6

3.5

1

UK Ordnance:

Small arms <9mm calibre

0.1

-

0.2

Medium calibre <20mm

0.2

0.2

0.3

Mortars <2inch

0.4

0.6

0.4

Mortars <3inch

0.5

0.8

0.4

Shells <3inch

0.5

0.8

0.4

Practice bombs <8 pound

Unknown

Practice bombs <25 pound

Unknown

These detection depths are an absolute maximum in ideal conditions and it is considered that in almost all cases, the detection depths will be considerably less than that stated in this table.

We strongly recommend that customers ask contractors for 3rd party evidence that their equipment / survey method is capable of achieving the client’s survey objectives before commissioning work. Clearly the CIRIA-sponsored industry shake-up is long overdue.

London office opens

Zetica have teamed up with John Newton & Partners (www.jnpgroup.co.uk) to share an office in Swanley, off Junction 3 of the M25 in the Thames Gateway region.

We value personal relationships with clients and see this move as a way to respond quicker to queries and improve our understanding of site specific issues at the heart of the action in London.

London office opensHorizon House
Station Approach
Swanley
Kent BR8 8HY
Tel: 01322 612140
Fax: 01322 612141
Email: thamesgateway@zetica.com

Contact Us:
Zetica logo

www.zetica.com
info@zetica.com
Tel: 01993-706767
Tel: 01322-612140

CEO
asger@zetica.com

Managing Director
mike@zetica.com

Technical Manager
jon@zetica.com

Copyright © 2005

Win a free day of utilities scanning

Following a successful utilities survey for Midlands firm, the Avoncroft Group, to trace lost drains, and an excellent response from clients to our original free survey offer, we’d like to extend the offer for one more day to carry out a free full day’s utilities mapping.

Zetica offers the industry’s most comprehensive service to map buried metallic and non-metallic utilities using the latest remote sensing equipment including the RD4000, SeekTech’s SR-20, multi-channel GPR, and EM profiling. Our well trained teams will trace and identify as many utilities as is physically possible.

This offer covers all fees including mob/demob (within 150mi of Oxford), field work and reporting for a day’s fieldwork.

Click here to register to be in the draw which will be held on the 1st December 2005. Click here to download utilities brochure.

Lunchtime Seminars

Lunchtime seminars imageZetica offer a popular Geological Society registered seminar, with CPD points, on the uses and abuses of geophysics. Engineers are brought up to date on the latest geophysical methods available in the market place and interesting areas of research and development. The presentation normally lasts 30 – 40 minutes and is case history-based with a 15 minute discussion session following.

Click here to email Ellen Stevens to discuss your requirements and arrange a seminar at your offices.