Response of municipal solid waste to mechanical compression

The compressibility of municipal solid waste (MSW) is of engineering interest as it affects the short-term and long-term performance of landfills, as well as their expansion, closure, and postclosure development. An assessment of the field settlement behavior of MSW can be reliably executed only when the various mechanisms contributing to the settlement are properly taken into account. A comprehensive large-size experimental testing program that involved a total of 143 one-dimensional compression tests from five landfills, in Arizona, California, Michigan, and Texas of the United States as well as Greece was executed to systematically assess the compressibility characteristics of MSW subjected to a compressive load. Emphasis is given to the influence of waste structure, waste composition, unit weight, and confining stress on the compressibility parameters that are used in engineering practice, such as the constrained modulus and compression ratio, as well as long-term compression ratio due to mechanical creep only. The effect of waste composition and unit weight on the compressibility parameters is quantified. It is also found that the type of waste constituent (i.e., paper, plastic, or wood), as well as the waste’s anisotropic structure can have an effect on the compressibility characteristics of soil-waste mixtures. The proposed relationships can be used to estimate compressibility parameters of MSW at any degradation state as long as the waste composition and unit weight are known

Ground vibration measurements near impact pile driving

Pile driving is a complex dynamic process where little insight has been garnered in terms of the energy transfer from the driver to the soil and surrounding structures. Ground motion measurements during driving of full scale steel H-piles with diesel hammers are presented. The key feature of this work is the in-depth sensor installation starting very close to the pile (0.2 m), at other radial distances from the pile, and at various depths in the ground. Differences in wave sources from the tip and the shaft of the pile as well as wave attenuation coefficients are revealed from the sensor measurements. Attenuation relationships fitted through the data could be used to predict ground motion that could cause shakedown settlement. A conventional line array of surface mounted geophones was also used and results are presented

A Review of Numerical Models for Slab-Asphalt Track Railways

Higher train speeds and heavier axle loads trigger elevated stresses and vibrations in the track, potentially increasing track deterioration rates and maintenance costs. Alternative track forms made of combinations of reinforced concrete and asphalt layers have been developed. A thorough understanding of the slab and asphalt tracks is needed to investigate track performance. Thus, analytical and numerical models have been developed and validated by many researchers. This paper reviews numerical models developed to investigate railway track performance. The synthesis of major finite element models is described in detail, highlighting the main components and their outputs. For slab track models, the use of a structural asphalt layer within the railway track remains an active research topic and firm conclusions on its efficacy are not yet available. It can be expected that slab track structures will also be affected by train-induced ground vibrations. There is thus a gap in the literature regarding the measurement of dynamic effects on high-speed railway lines, and further research is needed to investigate the dynamic behaviour of slab–asphalt track systems. In this review, novel solutions for mitigating the vibrations in high-speed rail are discussed and compared. The use of asphalt material in railways appears to have beneficial effects, such as increasing the bearing capacity and stiffness of the structure and improving its dynamic performance and responses, particularly under high-speed train loads

H-pile driving induced vibrations: reduced-scale laboratory testing and numerical analysis

Ground vibrations due to impact pile driving operations can become a major concern when affecting nearby structures and underground utilities. In an effort to better understand the transmission and dissipation of energy into the ground during impact pile installation, reduced-scale pile driving tests were conducted in an indoor cylindrical (6.5 m diameter and 1.8 m deep) sand pit at the University of Michigan. Sensors were placed at various depths from the ground surface and distances from the driven pile to record ground motions. In addition, the model pile was equipped with the pile driving analyzer (PDA) system to accurately assess the energy transfer from hammer to pile. The pile installation process was then simulated using 3D finite element (FE) dynamic analyses. The combination of ground vibration monitoring data and records of the impact force from the PDA testing collected from the small-scale pile driving tests in a controlled laboratory environment, offer a great opportunity to validate the numerical code. The recorded ground motion measurements from the impact driving of the model pile are compared with the calculated velocity-time histories from the FE numerical simulation of the pile driving test. Both measured and calculated ground motions verify the hypothesis of the wave propagation field generated by impact driven piles, as presented by Woods (1997)

Assessment of Accuracy and Performance of Terrestrial Laser Scanner in Monitoring of Retaining Walls

[EN] Retaining walls are a critical infrastructure of transportation networks and the monitoring of their condition is crucial for the efficient and reliable maintenance of the network. The condition of retaining walls is frequently assessed using qualitative criteria and visual inspection, which are susceptible to human-bias and errors. To improve the management of these structures, reducing the probability of failure and the maintenance costs, it is critical to develop more efficient, reliable and quantitative monitoring approaches for these structures. The current study aims to evaluate the performance of Terrestrial Laser Scanner (TLS) in deformation monitoring of retaining walls, based on the analysis of single scans (without registering the point clouds to build 3D models). The evaluation was based on a controlled experiment, where a wooden frame (1.5m x 1m) was used to simulate deformation scenarios for retaining walls, with an amplitude between 2 to 16 mm. A Leica RTC360 scanner was used to scan the wooden frame from distances varying between 10 to 27 m and angles varying between 0° to 20°. Five methods were applied to analyse the laser-scanner data and estimate the displacement: a target-based approach and four cloud-based approaches including the Cloud-to-Cloud (C2C), the Cloud-to-Mesh (C2M), the Multiscale-Model-to-Model-Cloud-Comparison (M3C2), and an alternative cloud-based method where the mean average of the point-cloud was used to estimate the displacement in the axis of the deformation. A Robotic Total Station Leica TS30 was also used to measure the deformation of the wooden frame and provide the ground truth values of the introduced deformation for each scenario. The results showed that the RTC360 had an accuracy of 1.3 mm with a confidence level of 95%.Algadhi, A.; Psimoulis, P.; Grizi, A.; Neves, L. (2023). Assessment of Accuracy and Performance of Terrestrial Laser Scanner in Monitoring of Retaining Walls. Editorial Universitat Politècnica de València. 467-473. https://doi.org/10.4995/JISDM2022.2022.1391746747

Effect of Pile-Driving Induced Vibrations on Nearby Structures and Other Assets

The work described here represents an attempt to understand the mechanisms of energy transfer from steel H-piles driven with diesel hammers to the surrounding soil and the energy attenuation through the soil by measuring ground motion vibrations in the near vicinity of the pile. Attenuation rates of vibration decay with radial distance from the driven pile were calculated. A spreadsheet tool was developed to estimate distances from the pile at which the threshold settlement vibrations may be exceeded