| 1. |
- Theland, Freddie, et al.
(author)
-
Assessment of small-strain characteristics for vibration predictions in a Swedish clay deposit
-
Other publication (other academic/artistic)abstract
- Environmental vibrations induced by human activities such as traffic, construction or industrial manufacturing can cause disturbance among residents or to vibration sensitive equipment inbuildings. In Sweden, geological formations of soft clay overlying a stiff bedrock are soil conditions prone to ground vibrations that are encountered both in urban areas and along parts of the national railway network. This paper presents an extensive investigation of the small-strain soil properties for the prediction of environmental ground vibrations in a shallow clay where the bedrock is situated at 7.5 m depth. The small-strain properties are estimated using available empirical correlations, bender elements, seismic cone penetration tests, seismic refraction and inversion of surface wave dispersion and attenuation curves. The results are synthesised into a dynamic layered soil model which is validated by measurements at the soil’s surface at source-receiver distances up to 90 m in the frequency range 1–80 Hz. Analyses of uncertainties in the estimated values of wave speeds and material damping are performed by model investigations, indicating that surface wave tests overestimate the damping compared to bender element tests. The properties of the topmost unsaturated part of the soil is found to have a significant influenceon the response at large distances, caused by critically refracted P-waves resonating in the top layer.
|
|
| 2. |
- Theland, Freddie, et al.
(author)
-
Assessment of small-strain characteristics for vibration predictions in a Swedish clay deposit
- 2021
-
In: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261 .- 1879-341X. ; 150
-
Journal article (peer-reviewed)abstract
- Environmental vibrations induced by human activities such as traffic, construction or industrial manufacturing can cause disturbance among residents or to vibration sensitive equipment in buildings. In Sweden, geological formations of soft clay overlying a stiff bedrock are soil conditions prone to ground vibrations that are encountered both in urban areas and along parts of the national railway network. This paper presents an extensive investigation of the small-strain soil properties for the prediction of environmental ground vibrations in a shallow clay where the bedrock is situated at 7.5 m depth. The small-strain properties are estimated using available empirical correlations, bender elements, seismic cone penetration tests, seismic refraction and inversion of surface wave dispersion and attenuation curves. The results are synthesised into a dynamic layered soil model which is validated by measurements at the soil's surface at source-receiver distances up to 90 m in the frequency range 1-80 Hz. Analyses of uncertainties in the estimated values of wave speeds and material damping are performed by model investigations, indicating that surface wave tests overestimate the damping compared to bender element tests. The properties of the topmost unsaturated part of the soil is found to have a significant influence on the response at large distances, caused by critically refracted P-waves resonating in the top layer.
|
|
| 3. |
- Theland, Freddie, 1989-, et al.
(author)
-
Dynamic response of driven end-bearing piles and a pile group in soft clay: an experimental validation study
-
Other publication (other academic/artistic)abstract
- This paper presents an extensive measurement campaign of the dynamic response of driven end-bearing piles and a pile group in soft clay. Results from measurements conducted on the free-top piles and and the piles joined in a concrete cap are presented. The measured frequency responses are subsequently used to obtain the impedances, characterising the dynamic stiffness and damping of the piles and the pile foundation. The piles are instrumented with accelerometers at several points along the length of the piles which allows to validate the dynamic motion of the piles atdepth due to pile head and pile cap excitation. Numerical predictions based solely on information of the small-strain soil properties obtained from extensive site investigations are compared to the experimental results. The numerical model captures the pile-soil-pile interactions and the motion of the piles within the soil well, suggesting that reliable predictions can be made for the considered soil conditions if the small-strain soil properties are well known.
|
|
| 4. |
- Theland, Freddie, 1989-
(author)
-
Prediction and experimental validation of dynamic soil-structure interaction of an end-bearing pile foundation in soft clay
- 2021
-
Licentiate thesis (other academic/artistic)abstract
- In the built environment, human activities such as railway and road traffic, constructionworks or industrial manufacturing can give rise to ground borne vibrations. Such vibrations become a concern in urban areas as they can cause human discomfort or disruption of vibration sensitive equipment in buildings. In Sweden, geological formations of soft clay soils overlying till and a high quality bedrock are encountered in densely populated areas, which are soil conditions that are prone to high levels of ground borne vibrations. Under such soil conditions, end-bearing piles are often used in the design of building foundations. The dynamic response of a building is governed by the interaction between the soil and the foundation. It is therefore essential that models used for vibration predictions are able to capture the dynamic soil-structure interaction of pile foundations.The purpose of this thesis is to experimentally and numerically investigate dynamic soil-structure interaction of an end-bearing pile group in clay by constructing a test foundation of realistic dimensions. The small-strain properties in a shallow clay deposit are estimated using different site investigation and laboratory methods. The results are synthesised into a representative soil model to compute the free-field surface response, which is validated with vibration measurements performed at the site. It is found that detailed information regarding material damping in the clay and the topmost soil layer both have a profound influence on the predicted surface response, especially with an increasing distance from the source.Dynamic impedances of four end-bearing concrete piles driven at the site are measured. Pile-soil-pile interaction is investigated by measuring the response of the neighbour piles when one of the piles in the group is excited. The square pile group is subsequently joined in a concrete cap and measurements of the impedances of the pilegroup and acceleration measurements within the piles at depth are performed. A numerical model based on the identified soil properties is implemented and validated by the measurements. A good agreement between the predicted and measured responses and impedances of the pile group foundation is found, establishing confidence in the ability to predict the dynamic characteristics of end-bearing pile foundations under the studied soil conditions.
|
|
| 5. |
- Theland, Freddie, et al.
(author)
-
Soil-structure interaction of an end-bearing pile foundation : Design of an experimental case study
- 2020
-
In: Proceedings of the International Conference on Structural Dynamic , EURODYN. - : European Association for Structural Dynamics. ; , s. 2846-2856
-
Conference paper (peer-reviewed)abstract
- The construction of apartment and office buildings close to road or rail traffic is becoming more frequent in urban areas. These sites are however prone to issues of disturbing vibrations in nearby buildings induced by traffic. In Sweden, designing building foundations with pre-fabricated end-bearing concrete piles is often a necessary and economical measure when soil conditions are poor. Although pile groups have been studied extensively in the context of seismic analysis, there are limited experimental results on the response of end-bearing pile groups due to ground vibration evoked by sources acting on the soil's surface. This paper presents the design of an experimental case study of an end-bearing pile group, aimed at validating models for predicting vibration levels in piled buildings. The test site is presented with results from geotechnical and geophysical site investigations. The experimental setup is outlined, describing measurements taken at each stage of construction of the pile group. Results from numerical simulations demonstrate a different behaviour of the pile group in comparison to an equally large surface foundation.
|
|
| 6. |
- Theland, Freddie, et al.
(author)
-
The influence of near-surface soil layer resonance on vibrations in pile foundations
- 2023
-
In: Current Perspectives and New Directions in Mechanics, Modelling and Design of Structural Systems. - London : Informa UK Limited. ; , s. 84-89
-
Conference paper (peer-reviewed)abstract
- This paper investigates the influence of an unsaturated layer in a soft soil on the dynamic response of piles subjected to an incident wave field caused by a vertical surface load. The free field response is compared to the response of single floating and end-bearing piles, and different configurations of square end-bearing pile groups. Simulations are made using a finite element model with perfectly matched layers where the incident wave field is computed from a separate source model employing a subdomain formulation. The presence of the unsaturated layer results in a resonance phenomenon in the top layer, amplifying critically refracted waves as they reach the surface. The associated response is shown to be significantly lower for concrete piles subjected to the same incident loading and practically independent of the pile end condition, in contrast to the response associated with the incident surface waves. For small end-bearing pile groups, the response caused by surface waves are further reduced while the response due to layer resonance show no further reduction. As a consequence, the frequency content associated with the layer resonance might constitute the dominating part of the vertical velocity response for end-bearing pile groups.
|
|
