In Boskoop, a new residential area is being constructed with the name of ‘Waterrijk’, which will consist of Waterrijk-West and Waterrijk-Boomgaard. In this new residential district, a total of 444 single-family houses and apartments will be realised as well as a so-called ‘Brede’ school.
In view of the settlement problems in previous house-construction projects in the vicinity and the consequently high maintenance costs, the Boskoop Municipal Council has required a relatively low residual settlement after the building site is ready for construction (handover).
In this project, it has been decided to replace a section of the weak soil (peat) with stronger soil, in combination with the application of vertical drainage and preloading. This method has two advantages when compared with the traditional methods i.e.:
- The peat which is dug out has a commercial value as ‘potgrond’ (potting compost);
- The soil/ground improvement which replaces the peat is stiffer and hence gives far fewer settlement problems.
In order to be able to verify this approach as well as the possibility of making any adjustment during the project, GEO2 Engineering B.V. has drawn up a monitoring plan.
In this plan, by way of placing settlement beacons high (on existing ground level) and low (on the remaining weak soil), the settlement behaviour of both the ground improvement and the complete situation itself, can be monitored and, if necessary, adjusted.
The analysis of these settlement beacons is mainly done by using a ‘Winfit’software programme which has been developed by GEO2. Based on the results of these analyses, it was also possible (besides the verifications of the specified requirements for residual settlement), to determine more accurately the settlement parameters for future phases in the project.