Deformation measurements in levee reinforcement projects.

After more than 25 years, the world of environmental monitoring holds few secrets for Van Monsjou & Partners. The independent inspection and expertise agency, in addition to performing structural surveys and vibration and noise measurements, is busy performing accuracy water adjustments and deformation measurements. And this expertise is increasingly in demand in recent years on quay and dike reinforcement projects.

Van Monsjou & Partners works daily with thirteen motivated colleagues on a wide variety of projects. "Central to this is monitoring the environment and specifically mapping the quality and sensitivity of buildings and objects," says founder and owner Sander van Monsjou. "The current condition/position is carefully recorded in advance to then actively monitor for vibrations, misalignment, cracking, groundwater, noise, etc. during the execution of a project. Because we are broadly skilled in all monitoring work, our clients have only one point of contact for inspection and monitoring work."

Accuracy-matching

In recent years, Van Monsjou & Partners has increasingly been called in on dike strengthening projects. "For example, we have been active on the Markermeer dikes since 2015," Sander continues. "Well before the Alliance started working outside, all the properties in the immediate vicinity of the dike were mapped. Over a stretch of 33 kilometers between Hoorn and Durgerdam, more than 1,800 elevation marks have been attached to 450 properties and have been measured every six months since 2015 via precision water leveling. In this way, the normal course and subsidence behavior are charted over a long period of time. The measurements show, among other things, that buildings on piles show little to no settlement, while settlement-sensitive objects can settle about 2 to 5 mm per year. Thanks in part to these measurements, the Alliance can better assess during the work whether the work will affect the surroundings."

Deformation measurements

During more invasive work closer to buildings, such as pre-loading and vibrating sheet piles, you want to know exactly how nearby objects behave. "That's when height measurements are insufficient," Sander knows and continues: "and you also want to be able to check for horizontal displacements. By applying mini prisms near the corners of properties and measuring relative to fixed reference points, displacement can be determined with an accuracy of less than 2-3 mm."

Van Monsjou & Partners is currently performing deformation measurements on approximately 70 homes on the north side of Volendam as part of sand excavation. "In total, more than 200 mini-prisms have been installed here, which we measure biweekly," says Sander. Sander is proud of the fact that Van Monsjou & Partners may provide the monitoring on the Markermeer dikes. "It is an extensive, dynamic and very exciting project, also in a very beautiful setting."