Showing papers on "Settlement (structural) published in 2018"

Determination of earth pressure balance tunnel-related maximum surface settlement: a multivariate adaptive regression splines approach

Abstract: A major consideration in urban tunnel design is to estimate the ground movements and surface settlements associated with the tunnelling operations. Excessive ground movements may result in damage to adjacent buildings and utilities. Numerous empirical and analytical solutions have been proposed to relate the shield tunnel characteristics and surface/subsurface deformation. Numerical analyses, either 2D or 3D, have also been applied to such tunnelling problems. However, substantially fewer approaches have been developed for earth pressure balance (EPB) tunnelling. Based on instrumented data on ground deformation and shield operation from three separate EPB tunnelling projects in Singapore, this paper utilizes a multivariate adaptive regression splines (MARS) approach to establish relationships between the maximum surface settlement and the major influencing factors, including the operation parameters, the cover depth and the ground conditions. Since the method has the ability to map input to output patterns, MARS enables one to map all influencing parameters to surface settlements. The main advantages of MARS over other soft computing techniques such as ANN, RVM, SVM and GP are its capacity to produce a simple, easy-to-interpret model, its ability to estimate the contributions of the input variables, and its computational efficiency.

Materials for space exploration and settlement

Abstract: Space missions require materials that can preserve functional integrity under extreme conditions of heat, impact and radiation. This Comment outlines the materials properties needed for some of the most ambitious space missions and presents the design and testing principles before their incorporation.

Investigating the Long-Term Settlement of a Tunnel Built over Improved Loessial Foundation Soil Using Jet Grouting Technique

Abstract: Postconstruction settlement that occurs before a tunnel is in operation may significantly influence the tunnel’s long-term stability. The current study investigates such a tunnel, a three-l...

Undrained behaviour of intact soft clay under cyclic paths that match vehicle loading conditions

Abstract: Vehicle traffic loading appears to contribute significantly to long-term settlement beneath highways, airport runways, and metro lines in China. Wheel loading imposes cycles in both the magnitude a...

Settlement prediction of the rock-socketed piles through a new technique based on gene expression programming

Abstract: The settlement design of bored piles socketed into rock has received considerable attention. Although many design methods of pile settlement are recommended in the literature, proposing new/practical technique(s) with higher performance prediction is of advantage. A new model based on gene expression programming (GEP) is presented in this paper for predicting the settlement of the rock-socketed pile. To do this, 96 piles socketed in different types of rock (mostly granite) as part of the Klang Valley Mass Rapid Transit project, Malaysia, were studied. In order to propose a predictive model with higher performance prediction, a series of GEP analyses were conducted using the most important factors on pile settlement, i.e. ratio of length in soil layer to length in rock layer, ratio of total length to diameter, uniaxial compressive strength, standard penetration test and ultimate bearing capacity. For comparison purpose, using the same dataset, linear multiple regression (LMR) technique was also performed. After developing the equations, their prediction performances were checked through several performance indices. The results demonstrated the feasibility of GEP-based predictive model of settlement. Coefficients of determination (CoD) values of 0.872 and 0.861 for training and testing datasets of GEP equation, respectively, show superiority of this model in predicting pile settlement while these values were obtained as 0.835 and 0.751 for the LMR model. Moreover, root mean square error (RMSE) values of (1.293 and 1.656 for training and testing) and (1.737 and 1.767 for training and testing) were achieved for the developed GEP and LMR models, respectively.

Face stability analysis of shield-driven tunnels shallowly buried in dry sand using 1-g large-scale model tests

Abstract: This paper investigates the face stability of shield-driven tunnels shallowly buried in dry sand using 1-g large-scale model tests. A half-circular tunnel model with a rigid front face was designed and tested. The ground movement was mobilized by pulling the tunnel face backwards at different speeds. The support pressure at tunnel face, settlement at ground surface, and internal movement of soil body were measured by load cells, linear variable differential transducers, and a camera, respectively, and the progress of face failure was observed through a transparent lateral wall of model tank. The tests show that, as the tunnel face moves backwards, the support pressure at the tunnel face drops sharply initially, then rebounds slightly, and tends to be stabilized at the end. Similarly, the ground surface settlement shows a three-stage variation pattern. Using the particle image velocimetry technique, the particle movement, shear strain, and vortex location of soil are analyzed. The variation of support pressure and ground surface settlement related to the internal movement of soil particles is discussed. The impact of the tunnel face moving speed on the face stability is discussed. As the tunnel face moves relatively fast, soil failure originates from a height above tunnel invert and an analytical model is developed to analyze such failure.

Multi-Scale Analysis of the Relationship between Land Subsidence and Buildings: A Case Study in an Eastern Beijing Urban Area Using the PS-InSAR Technique

Abstract: Beijing is severely affected by land subsidence, and rapid urbanisation and building construction might accelerate the land subsidence process. Based on 39 Envisat Advanced Synthetic Aperture Radar (ASAR) images acquired between 2003–2010, 55 TerraSAR-X images acquired between 2010–2016, and urban building information, we analysed the relationship between land subsidence and buildings at the regional, block, and building scales. The results show that the surface displacement rate in the Beijing urban area ranged from −109 mm/year to +13 mm/year between 2003–2010, and from −151 mm/year to +19 mm/year between 2010–2016; two subsidence bowls were mainly distributed in the eastern part of the Chaoyang District. The displacement rate agreed well with the levelling measurements, with an average bias of less than six mm/year. At the regional scale, the spatial pattern of land subsidence was mainly controlled by groundwater extraction, compressible layer thickness, and geological faults. Subsidence centres were located in the area around ground water funnels with a compressible layer depth of 50–70 m. The block-scale analysis demonstrated a clear correlation between the block construction age and the spatial unevenness of subsidence. The blocks constructed between 1998–2005 and after 2005 showed considerably more subsidence unevenness and temporal instability than the blocks constructed before 1998 during both time periods. The examination of the new blocks showed that the spatial unevenness increased with building volume variability. For the 16 blocks with a high building volume, variability, and subsidence unevenness, the building-scale analysis showed a positive relationship between building volume and settlement in most blocks, although the R2 was lower than 0.5. The results indicate that intense building construction in urban areas could cause differential settlement at the block scale in Beijing, while the settlement of single buildings could be influenced by the integrated effects of building volume, foundation structures, and the hydrogeological background.

Manipulation in the VIX

Abstract: At the settlement time of the VIX Volatility Index, volume spikes on SP editorial decision June 19, 2017 by Editor Robin Greenwood.

Displacement and Stress Characteristics of Tunnel Foundation in Collapsible Loess Ground Reinforced by Jet Grouting Columns

Abstract: Collapsible loess tunnel foundation reinforcement is a new challenge in the construction process of tunnel engineering. According to the field displacement and stress monitoring of the Fujiayao loess tunnel, this paper investigates the reinforcing effect of a high-pressure jet grouting pile on a collapsible loess tunnel foundation in the deep large-span tunnel. The field monitoring method was employed to address the performance of tunnel foundation settlement, additional stress, earth pressure, rock pressure, etc. The results indicate that the stress on the pile tops and the earth pressure between piles increase gradually over time in two stages: stress increases rapidly in the first 45 days and, after this period, stress tends to gradually stabilize. Further, stress increases uniformly with the distance from the centerline of the tunnel, and the rock pressure of the tunnel sidewalls tends to be stable within two months of being constructed. Additional stress on the tunnel foundation increases linearly with time, and it is uniformly distributed in the vertical and horizontal directions of the tunnel section. Settlement of the tunnel foundation also gradually increases with time, and it tends to be stable at 50 days from the time of construction. Additionally, the settlements of different monitoring points are similar at the same depth. The research results will further improve the theoretical knowledge of tunnel bottom reinforcement in the loess tunnel, which not only can effectively guide the design and construction of the loess tunnel and reduce disease treatment cost but also can provide the necessary basic research data and scientific theoretical basis for revision of the corresponding specifications of highway tunnels and railway tunnels.

HISDAC-US, historical settlement data compilation for the conterminous United States over 200 years

Abstract: Human settlement plays a key role in understanding social processes such as urbanization and interactions between human and environmental systems but not much is known about the landscape evolution before the era of operational remote sensing technology. In this study, housing and property databases are used to create new gridded settlement layers describing human settlement processes at fine spatial and temporal resolution in the conterminous United States between 1810 and 2015. The main products are a raster composite layer representing the year of first settlement, and a raster time series of built-up intensity representing the sum of building areas in a pixel. Several accompanying uncertainty surfaces are provided to ensure the user is informed about inherent spatial, temporal and thematic uncertainty in the data. A validation study using high quality reference data confirms high levels of accuracy of the resulting data products. These settlement data will be of great interest in disciplines in which the long-term evolution of human settlement represents crucial information to explore novel research questions. Machine-accessible metadata file describing the reported data (ISA-Tab format)

Study on the safe value of multi-pier settlement for simply supported girder bridges in high-speed railways

Abstract: This paper presents a method to analyse the influence of multi-pier settlement on the train–track–bridge coupled dynamic system, and to determine the safe value of the continuous multi-pier settlem...

Long-Term Performance of Pile-Supported Ballastless Track-Bed at Various Water Levels

Abstract: In recent years, the constructions of pile-supported ballastless track-bed have been developed rapidly in China. It appears important to assess the accumulative settlement of this kind of track-bed after years of operation, especially under unfavorable conditions, such as the rising of water level. In this study, a full-scale physical model simulating the pile-supported ballastless track-bed was established. The soil arching effect was previously developed in this model by draining out water in the water bags among the pile caps. The effects of water level and loading cycle on the accumulative settlement of this model were investigated following four testing procedures: water level rising, cyclic loading at high water level, water level lowering, and cyclic loading at low water level. The results indicated that the total accumulative settlement of the track-bed increased rapidly in the beginning of loading and tended to stabilize as the loading cycle increased at high water level, whereas the value varied slightly when loading at low water level. The distribution of the accumulative settlement inside the subgrade at the end of loading with high water level and at the end of this test both presented parabolic shaped variation trends, with the peak point occurring above the water bag and lower values developing above the pile cap. At the high water level, a modified model was applied to estimate the accumulative settlement of the unsaturated zone above the water level (height of soil arch), and the fitting parameters in this model were precalibrated using the testing data. The estimated results revealed that the deformation of the unsaturated zone above the water level accounted for a minor portion of that of the whole tack-bed. By contrast, the zone below the water level is the dominant factor to influence the accumulative settlement of the whole track-bed. From a practical point of view, a well-performing drainage system should be set up to avoid the rising of water level.