Soil Creep Effect on Time-Dependent Deformation of Deep Braced Excavation

This paper describes recent advances in the effect of soil creep on the time-dependent deformation of deep braced excavation. The effect of soil creep is generally investigated using the observational method and the plain-strain numerical simulation method. The observational method is more applicable for deep braced excavations in soft clays constructed using the top-down method. The plain-strain numerical simulation method can be conveniently used for parametric analysis, but it is unable to capture the spatial characteristics of soil creep effect on lateral wall deflections and ground movements. The additional lateral wall deflections and ground movements that are generated due to the soil creep effect can account for as large as 30% of the total displacements, which highlights the importance of considering the effect of soil creep in deep braced excavations through soft clays. The magnitude of the displacements due to soil creep depends on various factors, such as excavation depth, elapsed period, unsupported length, and strut stiffness. Parametric analyses have indicated several effective measures that can be taken in practice to mitigate the detrimental effect of soil creep on the deformation of deep braced excavation. Based on the literature review, potential directions of the related future research work are discussed. This paper should be beneficial for both researchers and engineers focusing on mitigating the adverse effect of soil creep on the stability of deep braced excavations.

Examination of Structures Built with Tunnel Formwork in Terms of Strength and Cost according to the Earthquake Regulations of 2007 and 2018

Turkey has always been exposed to active fault lines passing through and unpredictable seismic activities. These ground movements have always been one of the important issues in our country, which have led to great destruction and loss of lives and property in its past. For this reason, our earthquake regulations, which aim to design more accurately against earthquake movements, are continuously made improvements. In this study, the analysis of structures built with tunnel formwork system which is popular today with the new earthquake regulations entered into force in 2018, and the strength and cost according to the old earthquake regulation in terms of what differences will occur. In addition to the study, we investigated how the number of floors and regular floor plans affects the results. For this purpose, two types of structures were covered with 5, 10, and 15 storey models created, first in the 2007 earthquake regulation; then, in the 2018 earthquake regulation, design analysis was carried out. As a result, the new earthquake regulation, which came into force in 2018, led to more realistic results as it provides more accurate environmental inputs used in design analysis. Earthquake loads affecting floors increased by 3.9% for 5 storey in regular structures, decreasing by 38.4% for 10 stories and 43.3% for 15 stories. More irregular structures increased 7.3% for 5 storey, 10-storey structures decreased by 38.9%, and 15-storey structures decreased by 43.6%. In terms of cost, there was a 0.07% increase in total cost in 5-storey buildings, 2.45% in 10-storey buildings, and a 3.91% reduction in 15-storey buildings. In addition to these results, an empirical formula that estimates m2 prices depending on the number of floors was obtained.

Forensic investigation of Gumbasa irrigation main canal damage due to large-scale flow liquefaction in Sibalaya caused by the 2018 Sulawesi Earthquake

This study conducted an extensive soil investigation in the Sibalaya liquefaction area to identify the Gumbasa main canal’s damage triggered by flow liquefaction. Several field tests and trenches with approximately 4 m were excavated to observe liquefied soil layers directly near the canal. A borehole, standard penetration test, and multichannel analysis surface waves (MASW) were performed beside the trench to obtain each layer’s penetration resistance. This research aims to understand the landslide’s whole aspect. The ground movements were analyzed by using satellite photos before and after the earthquake. The displacement of the main canal, the typical damage inventory, and the proposed reconstruction of the main canal are the focus of this study. As a result of the forensic investigation, the liquefied layers and debris flow contributing to the massive landslide were identified to impact the primary canal. The typical damage of the canal was due to surface rupture that occurred both horizontally and vertically. A solution for reconstructing the main canal is to use a flexible pipe canal structure. That will be resilient to future earthquake and ground movements, stabilize the ground downslope of the existing canal to limit the risk of future lateral movement in future earth tremors.

Effects of Axial Relative Ground Movement on Small Diameter Polyethylene Piping in Loose Sand

Small diameter (42 mm) medium density polyethylene (MDPE) pipes are widely used in the gas distribution system in Canada and other countries. They are sometimes exposed to ground movements resulting from landslides or earthquakes. The current design guidelines for evaluating the pipes subjected to ground movement were developed for steel pipes of larger diameters and may not apply to flexible MDPE pipes. This paper evaluates 42 mm diameter MDPE pipes buried in loose sand under axial relative ground movement for developing a design method for the pipes. MDPE is a viscoelastic material; therefore, the behaviour of MDPE pipes exposed to landslides would depend on the rate of ground movements. In this research, full-scale laboratory tests were conducted to investigate the responses of buried pipes under various rates of relative axial displacement. Finite element modelling of the tests was used to interpret the observed behaviour using the continuum mechanics framework. The study revealed that the pulling force on the pipe depends on the rate of relative ground displacement (pulling rate). The nondimensional pulling force possessed a nonlinear relationship with the pulling rate. A rate-dependent interface friction angle could be used to calculate the maximum pulling forces using the conventional design guidelines for the pipes in loose sand. Based on the pulling force, the pipe wall strains can be estimated using the methods available for larger diameter pipes.

GIS-Based Landslide Disaster Risk Areas and Ground Movements Mapping to Support Disaster Mitigation Activities (Case Study: Tasikmalaya Regency)

Tasikmalaya Regency is an area that is prone to landslides and ground movements. The availability of comprehensive and accurate information in controlling land use for regional development in areas prone to landslides and ground movements is very important for casualty prevention and other losses such as physical, social and economic. This information must be disseminated to the public as an early warning system to support disaster mitigation efforts. Identification of the characteristics of landslide and ground movement prone areas requires the mapping of risk areas to mitigate disasters. This can be done using Geographic Information System (GIS). This mapping activity was carried out using the method of collecting digital data from five vulnerability controlling factors of landslides and ground movements, namely rainfall, rock type, soil type, land cover and slope. The analysis is continued by weighting the factors that influence landslides and ground motion and then overlaying the five controlling factor maps (with their respective weight values) to produce a landslides and ground movement vulnerability level map which is then inputted into WebGIS. This map can then be used by local governments and the public as an information medium to support disaster mitigation activities.

The inverse strength problem for evaluation of bending stresses in pipelines during ground movements

Three variants of the engineering solution of inverse problems regarding the strength of pipeline sections bent as a result of ground movements or during an earthquake are proposed. The feature of this approach consists in calculation of stresses not by the forces acting on the pipe, but by the displacements or deflections. Therefore, full-scale measurements of the detected deviation of the pipe position from the planned pipeline route should be taken as initial data for estimating the values of additional bending stresses. The first problem considered is the assessment of the risk of pipeline malfunction upon sagging or bulging of the supports of aboveground pipelines. The problem is solved in the beam approximation. The pipeline is considered a statically indeterminate beam, one of the supports of which is forcibly moved to a given distance. For a once statically indeterminate beam, a system of four equations — two equilibrium equations and two integral equations for deflections — was solved numerically. The calculated values of three reactions of the supports and the angle of rotation of the pipe section on the first support are used to calculate bending moments, stresses and deflection lines. The problem for a thrice statically indeterminate beam under strain loading was also solved. The second goal is to model the stress-strain state of the pipeline proceeding from the tables of experimental data on the values of pipe deflections and their coordinates. The problem was also solved numerically, using the procedures of smoothing, linear interpolation and sequential differentiation. It is shown that taking into account the possible ambiguous solution of the inverse problem, we should not rely on the calculated values of transverse forces and distributed loads. It is enough to limit ourselves to the second coordinate derivative of the deflection. The third goal is to prevent accidents at the design stage. It is proposed to create a list of normalized deflection functions for modeling possible emergency situations for pipeline sections placed in difficult ground-geological conditions and seismically dangerous zones. The examples of such functions are given.