The Netherlands is a densely populated country. Any situation where infrastructure needs to be extended there is a probability that this may interfere with existing structures in the vicinity; this may even involve a tunnel. As tunnels in general are not under piled, they may be vulnerable to imposed deformations or loads. Due to the soft soil in the Netherlands, new infrastructure, e.g. bridges will be built on piles; mostly driven piles. Pile driving due to its nature may create deformations and loads, as the soil original soil is displaced from the position of the pile. This volume needs to be absorbed either by compression or kinematically absorbed due to displacement of soil outward from the pile. Near the Thomassen tunnel in Rotterdam, piers need to be built for overbridging of the approach to the Thomassen tunnel in the extension of the Harbour Railway. In order to estimate the deformation effects of pile driving a test was performed on a nearby location. Pile intrusion was monitored with inclinometers at different distances to a series of test piles. The result was applied as input for 3D FEM analysis for the erection of one of the bridge piers. In this paper, test results will be discussed as also the results of the analyses.@en

Distributed temperature sensing (DTS) can be used to monitor the production process of diaphragm walls. DTS is able to differentiate between already present or fresh bentonite suspensions during refreshing of the bentonite slurry in the trench. During concrete casting, DTS is able to differentiate between the bentonite suspension and concrete. As a result, the continuity of the casting process and the arrival of good grade concrete at crucial locations in the trench can be monitored. Tests conducted on laboratory models provided reference information for interpretation of field data. Field experiences have shown the benefits of DTS tests and the predictive value of the reference measurements. Results are compared with crosshole sonic logging measurements at the same location.

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Quality control of diaphragm walls prior to excavation is often difficult. One technique that can be used to detect anomalies in diaphragm walls involves electrical resistance. Electrical resistance measurements across a diaphragm wall can (within a strict framework) be used to verify the presence of leaks in diaphragm walls as a supplement to crosshole sonic logging. From measurements around a test wall conducted in this study, it is concluded that the detectability of anomalies with electrical resistance decreases exponentially with the increasing distance between the measurement electrodes and the wall. Electrical resistance setups with two and four electrodes have been compared. For usable results, a four-electrode setup must be used in which the potential electrodes need to be placed very close to the wall (less than 0.2 m away). Based upon the test experience, a field setup for verification of a building pit consisting of diaphragm walls is suggested, as well as a setup for determining the quality of the concrete covering the rebar in quay walls constructed with diaphragm walls. @en

Diepwanden In de video van promovendus Rodriaan Spruit is te zien hoe onderzoek wordt gedaan naar de technieken om zwakke plekken in diepwanden op te sporen. Deze wanden worden in de grond gevormd, waardoor de kwaliteit soms lastig te controleren is. Crosshole Sonic Logging, een techniek gebaseerd op het meten van geluidsgolven, lijkt een goede oplossing.@en