Deep Residential Basement, Chelsea

1. Deep Residential Basement, Chelsea

2. Toureen Plant Toureen Contractors City Basements Groundworks RC Frames Petrol Filling Station Refurbishment Decommissioning Demolition

3. The Scope • 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 Basement Plan

4. The Scope 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

5. 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

6. 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

7. 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

8. The Solutions Traffic management • Purpose built gantry

9. The Solutions Traffic management • Made use of permanent works

10. The Solutions Traffic management • Designed to allow spoil removal, • concrete pumping and lifting of plant

11. The Solutions Retaining 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

12. The Solutions Retaining Walls

13. The Solutions Retaining Walls • Silent and vibration less • piling with minimum water • jetting • Temporary frame cut and • installed to suit on site • dimensions

14. The Solutions Retaining Walls • Existing house piled to limit • settlement • Contiguous retaining walls • installed from inside of house

15. Results of movement monitoring m m

16. m

17. The Solutions Retaining Walls • Install sheet piles outside boundary and extract.

18. The Solutions Tree Protection Zone • Limit disturbance in TRPZ

20. The Solutions Tree Protection Zone • Work in progress

21. The Solutions Tree Protection Zone • Offer better value with micro piles

22. The Solutions Tree Protection Zone • Reduce plant size and • space requirements

23. The Solutions Tree Protection Zone • Make use of permanent work piles • as king posts

24. The Solutions Managing Groundwater • Appreciating the problem

25. The Solutions Managing Groundwater

26. The Solutions Managing Groundwater

27. The Solutions Managing Groundwater • Forming cut off walls to stem water • flow

28. The Solutions Managing Groundwater • Deep drainage sumps

29. The Solutions Managing Groundwater • Pumping and disposal

30. The Solutions Programme • Top down vr bottom up

31. The Solutions Programme • Tower Crane

32. The Solutions Programme • Removal of soil

33. The Solutions Programme • Removal of spoil

34. The Solutions Programme • Working inside and • outside the property • simultaneously

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

36. 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

37. Summary • Quality work executed by skilled • operatives and tradesmen