Analysis of an Underground Structure Settlement Risk due to Tunneling:A case study from Tabriz, Iran

The tunnel of the Tabriz urban railway line 2 (TURL2), Iran, will pass through an underground commercial center onits way. Too little distance between the tunnel crown and the underground structure foundation will probably cause collapseor excessive settlement during the tunnel construction based on studied geotechnical conditions of the region. In this paper,a method of risk level assessment for various types of structures, such as frame and masonry structures, and various typesof foundation, such as continuous and isolated, is well defined and the risk level is classified. Moreover, the value of theunderground commercial center structure settlement is estimated using both empirical and numerical methods. The settlementrisk level of the commercial center structure is determined based on presented definitions about risk classification ofvarious types of structures. Consequently, tunneling processes in this section need a special monitoring system and consolidationmeasures before the passage of a tunnel boring machine

Geotechnical Site Assessment by Seismic Piezocone Test in North of Denmark

These days cone penetration tests (CPT) have gained more popularity as an alternative to the conventional laboratory tests for subsurface investigation and estimation of soil parameters. Due to increasing interest in soil dynamics in the last decades, there is a development of CPT as a seismic piezocone penetration test (SCPTU) which provides shear wave velocity measurements simultaneously with measurements of tip resistance (qc), sleeve friction (fs) and pore pressure (u). The results can be used for determination of deformation parameters of soil. In this regard there have been proposed different empirical correlations between cone data and shear wave velocity measurements to estimate geotechnical parameters but their validity still needs to be verified in a case study and uncertainty remains about the choice of empirical correlations. In this study a site at the East Harbor of Aalborg (sandy site) and another at the Harbor of Frederikshavn (clayey site) in Denmark, where several SCPTU tests have been conducted, are considered. The data were used and analyzed based on different correlations presented in the literature. The results are further compared and verified with the measurements of shear wave velocity achieved from SCPTU tests

Probabilistic examination of the change in eigenfrequencies of an offshore wind turbine under progressive scour incorporating soil spatial variability

The trend for development in the offshore wind sector is towards larger turbines in deeper water. This results in higher wind and wave loads on these dynamically sensitive structures. Monopiles are the preferred foundation solution for offshore wind structures and have a typical expected design life of 20 years. These foundations have strict serviceability tolerances (e.g. mudline rotation of less than 0.25° during operation). Accurate determination of the system frequency is critical in order to ensure satisfactory performance over the design life, yet determination of the system stiffness and in particular the operational soil stiffness remains a significant challenge. Offshore site investigations typically focus on the determination of the soil conditions using Cone Penetration Test (CPT) data. This test gives large volumes of high quality data on the soil conditions at the test location, which can be correlated to soil strength and stiffness parameters and used directly in pile capacity models. However, a combination of factors including; parameter transformation, natural variability, the relatively small volume of the overall sea bed tested and operational effects such as the potential for scour development during turbine operation lead to large uncertainties in the soil stiffness values used in design. In this paper, the effects of scour erosion around unprotected foundations on the design system frequencies of an offshore wind turbine is investigated numerically. To account for the uncertainty in soil-structure interaction stiffness for a given offshore site, a stochastic ground model is developed using the data resulting from CPTs as inputs. Results indicate that the greater the depth of scour, the less certain a frequency-based SHM technique would be in accurately assessing scour magnitude based solely on first natural frequency measurements. However, using Receiver Operating Characteristic (ROC) curve analysis, the chance of detecting the presence of scour from the output frequencies is improved significantly and even modest scour depths of 0.25 pile diameters can be detected

Geotechnical Site Assessment by Seismic Piezocone Test in North of Denmark

These days cone penetration tests (CPT) have gained more popularity as an alternative to the conventional laboratory tests for subsurface investigation and estimation of soil parameters. Due to increasing interest in soil dynamics in the last decades, there is a development of CPT as a seismic piezocone penetration test (SCPTU) which provides shear wave velocity measurements simultaneously with measurements of tip resistance (qc), sleeve friction (fs) and pore pressure (u). The results can be used for determination of deformation parameters of soil. In this regard there have been proposed different empirical correlations between cone data and shear wave velocity measurements to estimate geotechnical parameters but their validity still needs to be verified in a case study and uncertainty remains about the choice of empirical correlations. In this study a site at the East Harbor of Aalborg (sandy site) and another at the Harbor of Frederikshavn (clayey site) in Denmark, where sever al SCPTU tests have been conducted, are considered. The data were used and analyzed based on different correlations presented in the literature. The results are further compared and verified with the measurements of shear wave velocity achieved from SCPTU tests