In the city of Amsterdam, many structures, such as houses,bridges and quay walls, are founded on wooden piles. In order to gain insightinto the safety of such structures, assessment of the foundations is required.As part of an experimental framework assessing the safety of bridges and quaywalls in the city of Amsterdam, a number of piles are instrumented with fiberoptic sensors and load tested in compression. These tests aim to providedetailed information on the behavior of timber piles subjected to loading. Thisinformation can be used to determine the geotechnical bearing capacity of suchpiles. An in-depth analysis is conducted on 8 timber piles tested within thisframework.  The conducted analysis has resulted in a variation ofoutcomes. Without including the effects of residual loads, an average baseresistance of 130 kN is observed. Upon inclusion of residual loads the averagetrue base resistance increases to a value of 188 kN. The average shaftcapacities in the bearing sand layer for scenarios excluding and includingresidual effects are 48 and 60 kN respectively.  The correlation factor α_p is derived usingthree cone resistance averaging techniques. The Koppejan method hasconsistently resulted in the highest derived α_p factors withvalues of 1.09 and 1.61 for scenarios excluding and including residual loadsrespectively.  The scenario excluding residual effects has resulted in anaverage α_sof 0.009 for the bearing sand layer. Upon inclusion of residual loads, thederived α_sfactor for the first sand layer amounts to 0.012. This increase in shear forcesis also observed in the Pleistocene peat layer. Therefore, residual loadsredistribute the capacity of the piles by increasing the shaft resistance inthe bearing sand and Pleistocene peat, while simultaneously decreasing theshear stresses in the Holocene layers above.  Conclusively, timber pile characteristics such as variationin geometry and mechanical properties have significant effects on the capacityof the piles. Additionally, these variations result in fluctuations in thecalculated load distribution along the pile. Local smoothing of thesefluctuations results in higher apparent loads, most specifically at the pilebase. Therefore, smoothing algorithms are not implemented in this analysis. Thevariation in diameter along the entire length of each pile directly affects theload distribution. Despite this influence, no trend is observed for thevariation of α_p factors with respect to pile tip diameter. Anapparent relationship between the tapering of the pile in the bearing sandlayer and the derived α_s factors suggests that tapering effectivelyincreases the shear forces along the shaft in that layer.  Furthermore, the usage of fiber optic sensors on woodenpiles has proven to be effective. The variation in local behavior of wood isclearly illustrated through the conducted analysis. As a consequence of thebiological nature of wood, the local behavior of wooden piles is best capturedby sensing technologies measuring strains at high spatial frequencies.   ... Read more

The aim of this project is to elaborate upon the design proposal of a miniature cone penetration test device. The usage of CPTs in the geotechnical centrifuges has proven to be a reliable experimental method. The usage of a CPT in a centrifuge can provide determinant results for many applications of geotechnical experimentation. The usage of cone penetration tests in centrifuge modelling is a significant experimental method in geotechnical engineering. The measurement of cone resistance and pore-pressure during in-flight tests can provide valuable data to correlate with soil properties and material behaviour. Through the years, this method has proven to be reliable and repeatable and has helped in verifying correlations of laboratory measurements and field data. The inexpensive and time-efficient nature of centrifuge testing and the reliability of cone penetration testing complement each other. This method has many relevant applications and acts as an effective tool. A literature study is conducted to obtain practical information on the design process of minia- ture CPTs. The existing designs are studied and their specifics are compared to the boundary conditions of the centrifuge of Delft University of Technology. This apparatus is capable of con- ducting tests at 300 times the gravitational acceleration and can carry samples with widths up to 400 millimeters. Two sets of existing sample containers are considered in this project which define physical dimensional boundaries. These sample containers consist of rectangular and cylindrical boxes with defined dimensions. The existing boundaries are further analyzed with respect to boundary effects derived from previously conducted tests to define design specifications for a potential miniature probe. The definition of such boundaries set the basis of the design proposal. For the rectangular containers a miniature probe with a maximum diameter of 4 millimeters can be used. As for the cylindrical sample containers, miniature probes with maximum diameters of 7.5 and 9.5 millimeters are appropriate to be designed. The analyzed existing designs are then scaled and altered with respect to the determined boundary values and the proposal is further evaluated.
Three miniature CPTs are designed with diameters of 4, 7.5 and 9.5 millimeters. Each design has certain applications and can be used in specific scenarios. All three designs include modular load cells and sub-parts that can be replaced and altered. Each proposed device consists of a modular load cell designed based on required material properties to experience a minimum amount of 500 micro-strain without buckling. The first design, with a cone diameter of 4 millimeters, can be used in any container with a minimum width of 12 centimeters and for soil samples with a maximum average grain size of 200 micrometers. The second design, with a cone diameter of 7.5 millimeters, can be used in containers with a minimum width of 22.5 centimeters and is applicable to soil samples with a maximum average grain size of 270 micrometers. The final design, with a diameter of 9.5 millimeters, is meant to be used in sample containers of widths above 28.5 centimeters and for soil samples with a maximum average grain size of 340 micrometers. The designs are then evaluated with regards to manufacturing costs and feasibility. An estimation is made based on previously designed and patented devices and material catalogues provided by manufacturers. The cost of the first two designs are estimated to amount to 1580 to 2080 Euros, whereas the third design is estimated to cost 3080 to 3580 euros due to temperature compensated pore-pressure sensor that is included in the design. Upon further evaluation, the first design with a diameter of 4 millimeters is chosen as the most feasible and practical concept due to applicability and practicality of the design. ... Read more

The aim of this project is to focus on the effect of mechanical contrast and surface roughness as factors influencing the shear strength of the interface of different rock samples. The shear strength of an interface is significant in experimental projects that for instance address the containment and propagation analysis of hydraulic fractures.
A discontinuity can be defined as any type of interruption in mechanical and structural properties of a rock layer. The samples used in this project are mechanically discontinuous at the interface. These samples consist of 3 different sandstones, one granite and one monzodiorite samples. These samples were prepared to fit a certain casket that was specially designed for this project. The mechanical contrast between pairings of these samples were obtained through calculations for difference in unconfined compressive strength between the rock types. The samples were then placed in a direct shear box and sheared against each other to obtain shear force and vertical displacement profiles while under a specific normal load.
In three different sets of experiments, specific pairings of samples were analysed and processed. Each pairing showed a unique set of results which were then compared with one another. Each experiment set focused on a certain aspect. The first set of experiments focused on the effect of mechanical contrast. The second experiment set focused on the change in surface roughness caused by shearing at higher loads. The third set focused on the effect of predetermined changes on surface roughnesses and how this would affect the shear stress profiles.
The values obtained through these experiments were then mathematically processed and shear stresses and normal stresses were plotted against each other. From these plots the friction coefficients and angles of friction were calculated.
The results show that mechanical contrast has a direct effect on the shear stress profiles. A constant mechanical contrast of two different pairings of samples results in the same trend no matter what rock types were used. In other words, if two different pairs are sheared against each other with each pair having the same mechanical contrast, the shear stress profiles will have the same friction coefficient. The surface roughness also directly effects the shear stress profiles. The results showed that the higher the measure of surface roughness, the higher the shear stress will be. The predetermined surface roughnesses of the samples were 125 and 75 μm. ... Read more