Every construction project influences the surroundings. Especially when construction is done in urban areas, the consequences this has for the surroundings must be thoroughly investigated. Does the construction of the basement create an unacceptable damage-risk profile for the adjacent building? Will the discharge pipe continue to function if the adjacency is elevated? Are the vibrations due to driving piles or installing sheet piles acceptable? How long can the groundwater level be lowered so as not to adversely affect the surroundings?
CRUX is recognized by all insurers as a qualified party for conducting environmental-impact risk analyses to obtain the CAR insurance. Having a settlement risk analysis performed by CRUX may result in improved insurance conditions (premium, deductible), and it reduces the risks for the project developer, particularly with regard to the often-considerable costs of any delay in construction.
A settlement risk analysis may also play an important political role in showing the parties concerned and in particular owners of adjacencies that the developer/contractor has seriously and thoroughly had the risks assessed by an external and independent, highly-qualified party.
With the new tender forms, such as D&C, D&B, BVP and DBFM contracts, the most economically advantageous tender ('Economisch Meest Voordelige Inschrijving'; EMVI) plays an increasingly important role. Conducting a settlement risk analysis and preparing a good monitoring and management plan can significantly improve the score on points such as limiting and controlling damage and nuisance to the surroundings.
CRUX has unique expertise and experience in answering questions in the area of settlement risk assessment. We provide the following services within the field of settlement risk assessment:
For all projects, CRUX meticulously examines whether the nature of construction work gives reason for a preliminary investigation of the surrounding area.
The damage sensitivity of the adjacent buildings can be determined on the basis of archival research, visual inspections, structural assessments, measurements and possibly a foundation study. Not only are buildings studied, but also civil structures , cables and pipes, roads, water works and/or vibration-sensitive equipment.
Piling or vibrating piles and sheet piling cause vibrations in the ground, which extend into a certain impact area around the construction work. Existing structures located in this impact area are subjected to these vibrations via the foundation and can suffer damage as a result.
CRUX maps expected vibrations in advance by performing vibration predictions and tests vibration against the SBR-A measurement and assessment guideline relevant in the Netherlands for damage to buildings. Vibrations can also be tested against SBR-B (hindrance for persons) and SBR-C (failure of equipment). Where necessary, CRUX prepares set-ups for vibration tests to map the vibration impact on site.
Ground deformations are the foremost source of damage risks for the surroundings. Existing structures located in this impact area are subjected to these (change) distortions via the foundation and can suffer damage as a result.
The ground deformations resulting from construction work are calculated by CRUX with, among other methods, the computer programs PLAXIS 2D and 3D. With these programs, it is possible to consider the stress and deformation condition and the stability of a ground massif with a complicated geometry.
Damage predictions are performed in order to be able to take into account the consequences of settlements due to construction work. The information obtained from the adjacencies research and the deformation analyses is an important starting point for this.
The predictions are tested against standards, guidelines and design recommendations. To assess the likelihood of damage to structures, CRUX has developed its own calculation model based on Holger Netzel's graduate thesis. With the help of these design tools, an optimal design from the perspective of settlement risk assessment is created. This approach reflects the state-of-the-art in design practice domestically and abroad and has been successfully used by CRUX for damage predictions of adjacencies in small- and large-scale underground construction projects in an urban environment.
Where risks can be expected from the risk analyses, monitoring is a critical component. The monitoring precisely records the development of vibrations, deformations and groundwater levels during the execution.
CRUX works with expert parties to perform the monitor of specific vibrations, displacements and groundwater levels. By measuring on time, intervention can be done in time during construction to prevent damage to the surroundings.
A monitoring plan includes the description of the necessary measurements of vibrations, displacements and groundwater levels during the execution. The size and specifications of monitoring, the measuring frequency and the test values are determined by CRUX based on risk analyses.
Up to reaching the intervention value, the expectations for the settlement risk assessment and the damage risk profile from the risk analysis are met. If unforeseen deviations are detected based on measurements, whether implementing a (subsidence- or vibration-mitigating) measure is necessary can be determined in a timely way through feedback of the monitoring results with the damage predictions. CRUX can include such mitigating measures in advance in a management plan, so that in the case of any deviation during execution, it is immediately clear to everyone which measures can be applied to adjust the process.
The supervising of monitoring works and expert interpretation of the measurement results by CRUX, during execution, is an important factor in the case of a sudden (continuing) increase in deformation in having a rapid understanding of the cause of any deviations, the impact on the outcome of the risk analyses and the necessity of implementing mitigating measures.
Unfortunately, damage does sometimes occur as a result of construction projects. In that case, the cause must often be determined by means of an independent analysis. CRUX has the know-how, expertise and experience to perform thorough qualitative and/or mathematical analyses of the causal relationship between the work done and the damage that has occurred. CRUX frequently performs this (forensic engineering) work for insurers and legal parties (lawyers, courts).