Deep Residential Basement, Chelsea

Toureen Plant

Toureen Contractors

City Basements

GroundworksRC Frames

Petrol Filling StationRefurbishment

Decommissioning

Demolition

Create a 585m2 basement around a Grade II listed Victoria Villa utilising the entire footprint of the plot including front, side and rear garden

To maximize internal space the basement is to be built partially under and around a tree protected under a tree preservation order

The Scope

Basement Plan

To accommodate a swimming pool within the basement and allow for the garden to be reinstated above, the basement was up to 8.5m deep

The deeper parts of the basement are to be formed in water bearing River Terrace Gravels

The Scope

The Challenges• The site is in a prime West London residential neighbourhood

sensitive to construction traffic

• The semi detached property shares boundaries with another semi detached villa, a school and a mews house to the rear. The semi detached villa adjacent being particularly sensitive to movement/deflections

The Challenges• Maximise internal space in the basement

• The basement had to be formed below and around a tree root protection zone. The TRPZ could not be compromised or the roots damaged

The Challenges

• Managing or excluding ground water from the excavation

• Offload and distribute materials around an irregular site

• Overlap construction of basement with refurbishment of existing property

• Tight programme and good value

The SolutionsTraffic management

• Purpose built gantry

• Made use of permanent works

The SolutionsTraffic management

• Designed to allow spoil removal, concrete pumping and lifting of plant

The SolutionsTraffic management

The SolutionsRetaining Walls

• Limit deflections by using propped Larrson sheet piles

• Increase space in the basement by using sheet piles over secant piled wall. Incorporate sheet piles into permanent works to reduce thickness of wall.

• Use of Larrsen sheet piles over zero piles to reduce propping requirements and limit deflection

The SolutionsRetaining Walls

• Silent and vibration less piling with minimum water jetting

• Temporary frame cut and installed to suit on site dimensions

The SolutionsRetaining Walls

The SolutionsRetaining Walls

• Existing house piled to limit settlement

• Contiguous retaining walls installed from inside of house

• Results of movement monitoring

m

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-0.005

0.000

0.005Diff to Base - Eastings

TM1TM2TM3TM4TM5TM6TM7TM8TM9TM10TM11

m

09/06/2008

16/06/2008

23/06/2008

30/06/2008

07/07/2008

14/07/2008

21/07/2008

28/07/2008

04/08/2008

11/08/2008

18/08/2008

0.000

0.002

0.004

0.006

0.008

Diff to Base NorthingsTM1TM2TM3TM4TM5TM6TM7TM8TM9TM10TM11

11/06/...

18/06/...

25/06/...

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-0.0040-0.00200.00000.00200.0040

Diff to Base- LevelsTM1TM2TM3TM4TM5TM6TM7TM8TM9

m

The Solutions Retaining Walls

• Install sheet piles outside boundary and extract.

The SolutionsTree Protection Zone

• Limit disturbance in TRPZ

The SolutionsTree Protection Zone

• Work in progress

• Offer better value with micro piles

The SolutionsTree Protection Zone

• Reduce plant size and space requirements

The SolutionsTree Protection Zone

• Make use of permanent work piles as king posts

The SolutionsTree Protection Zone

The SolutionsManaging Groundwater

• Appreciating the problem

The SolutionsManaging Groundwater

The SolutionsManaging Groundwater

The SolutionsManaging Groundwater• Forming cut off walls to stem water

flow

The SolutionsManaging Groundwater• Deep drainage sumps

The SolutionsManaging Groundwater

• Pumping and disposal

The SolutionsProgramme

• Top down vr bottom up

The Solutions Programme

• Tower Crane

The Solutions Programme • Removal of soil

The Solutions Programme • Removal of spoil

The Solutions Programme

• Working inside and outside the property simultaneously

The Solutions Programme• Support of front portico and rear extension on temporary piles

Summary • Sequence of works allows work inside and outside of property simultaneously

• Choice of retaining walls, temporary works, tower crane and gantry improve safety, efficiency and productivity

• Bottom up approach allows better access, logistics and working conditions

• Alternative temporary works around TRPZ

• Shorter programme lead to better value

Summary • Quality work executed by skilled operatives and tradesmen