Civil Engineering/boundry wall

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Expert: - 2/10/2010


Question
Dear sir,

i need to construct a hollow block work boundary wall 4.5 meters high adjacent to my neighbors boundary wall,neighbors boundary wall is 4 meters high block wall having RCC FOUNDATION.now as per drawing my foundation level is about 2.5 meter below my neighbors boundary wall foundation. the foundation which i have to cast is rcc strip footing 1.2 meter wide and 30cm thick.
the wall length is about 30 meters.
is it possible to excavate in 3 metes panels ,and casting my wall foundations ,by providing supports to the neighbor wall. or
shoring will be required and i cant move ahead without shoring.
note that neighbor boundary wall foundation is only one meter below the existing ground level.

Answer
Hi Naseer,

This is quite a complex problem with potential danger of undermining the neighbors wall foundations. My first reaction is, why construct your wall if there is already one that separates your property from the neighbors?

If you do need to construct it, the solution depends on the type of soil and also on the ground level difference either side of the twin-walls, and any overburden too. If the neighbors GL is much higher than yours (based on what you are saying that your foundation is at a much lower level), then your wall for the 2.5+1.0=3.5m depth will need to act as a retaining wall, so a simple hollow block wall may not work. Also, your 1.2m wide foundation cannot legally extend past your boundary, so all of it will need to be like an eccentric footing.

In any case shoring is advisable to prevent damage to neighbors wall and you may also need to do some under-pinning.

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Arshad Khan

Expertise

I can answer any questions to do with civil and structural engineering consultancy and construction industry in East Africa and the Middle East, and specifically with the analysis and design of reinforced concrete structures. My particular expertise is in the aseismic design and optimisation of tall buildings.

Experience

Employment history: 36 years in Construction and consultancy in the UK, Kenya, Tanzania, Uganda, Ethiopia, Eritrea, South Africa, Somalia, Zambia, Austria, Bahrain, Kuwait, Doha and the U.A.E.

Organizations
.Fellow of Institution of Structural Engineers (UK) .Fellow of Institution of Civil Engineers(UK) .Member of the Institution of Engineers, Kenya .Registered Engineer, ERB, Kenya .Member of the Architectural Association of Kenya (Engineers Chapter) .Chartered Engineer (UK)

Publications
•1984: International Conference on the Art and Practice of Structural Design, London •1994: 3rd Int. Kerensky Conference in Structural Engineering, Singapore •2008: International Conference on High-Rise Towers, Abu Dhabi

Education/Credentials
BSc, 1st Class Hons, in Building Engineering, University of Bath, UK MSc in Concrete Structures and Technology, University of London. Diploma of Imperial College, UK.

Awards and Honors
•Science Congress Special Award (for 2-seater Hovercraft - 1968) •Institution of Civil Engineers Award for outstanding performance at Bath University (1975) •Concrete Society Postgraduate study Bursary Award (1976) •Consular Representative for British High Commission, Nairobi. (1995 to 1998) •Examiner for Institution of Civil Engineers Professional Interviews, Nairobi. (1997 to 1998) •Branch Representative in Vienna for PI assessment for Inst. of Struct. Engrs. (1999 to date)

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