Showing papers on "Settlement (structural) published in 2017"

Feasibility of Random-Forest Approach for Prediction of Ground Settlements Induced by the Construction of a Shield-Driven Tunnel

Abstract: Ground settlements above a tunnel as a result of tunnel construction can be predicted with the help of input variables that have direct physical significance Several empirical and artificial intelligence methods for estimating ground settlements have been established by researchers However, these methods have some limitations because the large number of influential factors involved makes tunnel–ground interaction complicated In this work, a random forest (RF) was developed and employed to predict ground settlements above tunnels To achieve this goal, tunnel geometry, geological properties, and construction parameters were investigated as input variables to utilize in the RF modeling, resulting in the maximum surface settlement value (Smax) and trough width (i) as the ground surface settlement index To demonstrate the applicability of the RF model, two data sets associated with different features, which were obtained from a detailed investigation of different tunnel projects published in litera

Identification of tunnel settlement caused by land subsidence in soft deposit of Shanghai

Abstract: This paper provides a straightforward way to evaluate tunnel settlement caused by land subsidence in the soft deposits of Shanghai. By analyzing field measurements of tunnel settlement and ...

Liquefaction effects and associated damages observed at the Wellington CentrePort from the 2016 Kaikoura earthquake

Abstract: Widespread liquefaction occurred in the end-dumped gravelly fills and hydraulically-placed dredged sandy fill at the CentrePort of Wellington as a result of the 14 November 2016 Mw7.8 Kaikoura earthquake. This liquefaction resulted in substantial global (mass) settlement and lateral movement (spreading) of the fills towards the sea, which adversely affected wharf structures and buildings constructed on shallow and deep foundations. This paper presents key observations from the QuakeCoRE-GEER post-earthquake reconnaissance efforts at the CentrePort Wellington. The different materials and methods used to construct the reclaimed land at CentrePort influenced the patterns of observed liquefaction and its effects. Areas of gravel liquefaction at the port are especially important due to the limited number of these case histories in the literature. Liquefaction-induced ground deformations caused the wharves to displace laterally and damage their piles and offloading equipment. Lateral ground extension and differential settlement damaged buildings, whereas buildings in areas of uniform ground settlement without lateral extension performed significantly better.

Numerical analysis of surface subsidence in asymmetric parallel highway tunnels

Abstract: Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good understanding for prediction of tunnel deformation and surface settlement during the engineering life of the structure. The deformational behaviour, design of sequential excavation and support of any jointed rock mass are challenging during underground construction. We have raised several commonly assumed issues while performing stability analysis of underground opening at shallow depth. For this purpose, Kainchi-mod Nerchowck twin tunnels (Himachal Pradesh, India) are taken for in-depth analysis of the stability of two asymmetric tunnels to address the influence of topography, twin tunnel dimension and geometry. The host rock encountered during excavation is composed mainly of moderately to highly jointed grey sandstone, maroon sandstone and siltstones. In contrast to equidimensional tunnels where the maximum subsidence is observed vertically above the centreline of the tunnel, the result from the present study shows shifting of the maximum subsidence away from the tunnel centreline. The maximum subsidence of 0.99 mm is observed at 4.54 m left to the escape tunnel centreline whereas the maximum subsidence of 3.14 mm is observed at 8.89 m right to the main tunnel centreline. This shifting clearly indicates the influence of undulating topography and in-equidimensional noncircular tunnel.

Long-term thermo-mechanical behavior of energy pile in dry sand

Abstract: A small-scale pile has been developed in the laboratory to investigate the thermo-mechanical behavior of energy piles subjected to a significant number of thermal cycles. The pile (20 mm external diameter), installed in dry sand, was initially loaded at its head to 0, 20, 40 and 60% of its ultimate bearing capacity (500 N). At the end of each loading step, 30 heating/cooling cycles were applied. The long-term behavior of the pile was observed in terms of head settlement, axial force profile, soil and pile temperature, and stress in soil. The results evidence the irreversible settlement of the pile head induced by thermal cycles under constant load head. In addition, the incremental irreversible settlement that accumulates after each thermal cycle decreases when the number of cycles increases. The evolution of irreversible pile head settlement versus number of cycles can be reasonably predicted by an asymptotic equation.

Deriving Spatio-Temporal Development of Ground Subsidence Due to Subway Construction and Operation in Delta Regions with PS-InSAR Data: A Case Study in Guangzhou, China

Abstract: Subways have been an important method for relieving traffic pressures in urban areas, but ground subsidence, during construction and operation, can be a serious problem as it may affect the safety of its operation and that of the surrounding buildings Thus, conducting long-term ground deformation monitoring and modeling for subway networks are essential Compared with traditional geodetic methods, the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique offers wider coverage and denser measurements along subway lines In this study, we mapped the surface deformation of the Guangzhou subway network with Advanced Synthetic Aperture Radar (ASAR) and Phased Array Type L-band Synthetic Aperture Radar (PALSAR) data using the Interferometric Point Target Analysis (IPTA) technique The results indicate that newly excavated tunnels have regional subsidence with an average rate of more than 8 mm/year, as found on Lines Two, Three, Six, and GuangFo (GF) Furthermore, we determined the spatio-temporal subsidence behavior of subways with PALSAR in delta areas using Peck’s formula and the logistic time model We estimated the tunneling-related parameters in soft soil areas, which had not been previously explored We examined a section of line GF, as an example, to estimate the ground settlement trough development The results showed the maximum settlement increased from −52 mm to −236 mm and its ground loss ratio ranged from 15–87% between 13 July 2008 and 19 January 2011 In addition, we found that the tunnels in line GF will become stable after a period of about 2300 days in peak subsidence areas The results show that the proposed approach can help explain the dynamic ground subsidence along a metro line This study can provide references for urban subway projects in delta areas, and for the risk assessment of nearby buildings and underground pipelines along metro lines

Evaluation of behaviors of earth and rockfill dams during construction and initial impounding using instrumentation data and numerical modeling

Abstract: In this study, the behavior of Gavoshan dam was evaluated during construction and the first impounding. A two-dimensional (2D) numerical analysis was conducted based on a finite difference method on the largest cross-section of the dam using the results of instrument measurements and back analysis. These evaluations will be completed in the case that back analysis is carried out in order to control the degree of the accuracy and the level of confidence of the measured behavior since each of the measurements could be controlled by comparing it to the result obtained from the numerical model. Following that, by comparing the results of the numerical analysis with the measured values, it is indicated that there is a proper consistency between these two values. Moreover, it was observed that the dam performance was suitable regarding the induced pore water pressure, the pore water pressure ratio ru, settlement, induced stresses, arching degree, and hydraulic fracturing probability during the construction and initial impounding periods. The results demonstrated that the maximum settlement of the core was 238 cm at the end of construction. In the following 6 years after construction (initial impounding and exploitation period), the accumulative settlement of the dam was 270 cm. It is clear that 88% of the total settlement of the dam took place during dam construction. The reason is that the clay core was smashed in the wet side, i.e. the optimum moisture content. Whereas the average curving ratio was 0.64 during dam construction; at the end of the initial impounding, the maximum amount of curving ratio in the upstream was 0.81, and the minimum (critical) amount in the downstream was 0.52. It was also concluded that this dam is safe in comparison with the behaviors of other similar dams in the world.

A statistical review of the behaviour of concrete-face rockfill dams based on case histories

Abstract: The concrete-face rockfill dam (CFRD) has become a preferred dam type, but its design remains largely based on past experiences. Understanding the behaviour of CFRDs is critical to the design and s...

Longwall surface subsidence control by technology of isolated overburden grout injection

Abstract: Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coalfields, which exacerbates the negative subsequences resulted from surface settlement. Therefore, effective approaches to control the ground subsidence are in urgent need for the Chinese coal mining industry. This paper presents a newly developed subsidence control technology: isolated overburden grout injection, including the theory, technique and applications. Relevant procedures such as injection system design, grouting material selection, borehole layout, grout take estimation and injection process design are proposed. The applicability of this technology has been demonstrated through physical modelling, field measurements, and case studies. Since 2009, the technology has been successfully applied to 14 longwall areas in 9 Chinese coal mines. The ultimate surface subsidence factors vary from 0.10 to 0.15. This method has a great potential to be popularized and performed where longwall mining are implemented under villages and ground infrastructures.

Paleoparasitological investigations on the Neolithic lakeside settlement of La Draga (Lake Banyoles, Spain):

Abstract: Paleoparasitological analyses were conducted on samples from the Neolithic lakeside settlement of La Draga in Spain (5320–4980 BC). Conventional microscopic analysis revealed the presence of tapewo...

Surface settlement prediction for EPB shield tunneling in sandy ground

Abstract: Ground volume loss induced by shield tunnel construction is the major factor leading to ground settlement and deformation. The general equations predicting surface settlement based on ground volume loss involve a settlement trough width coefficient (parameter i) which in previous models was set as a constant in both the transverse and longitudinal directions. In this work, the equations predicting surface settlement during the construction were modified by introducing the parameter j – the width coefficient in the longitudinal direction, assumed to be different from that in the transverse direction. A model shield machine was adopted to carry a laboratory test under 1 g to investigate surface settlement induced by earth-pressure-balance shield tunnel construction in unsaturated sandy soil. The surface settlement during the excavating observed in the test was compared with that predicted by general equations from previous studies and the modified. The results showed that surface settlement above shield machine obtained by the modified equation proposed here fits the test data better than those obtained by the general equations because of the introduced longitudinal width coefficient.

Settlement plates as monitoring devices for non-indigenous species in marine fouling communities

Abstract: Non-indigenous species (NIS) are one of the leading forces of change in coastal marine ecosystems and are often associated with fouling communities, especially the artificial structures of marinas and ports. As a result, monitoring of marine fouling communities is crucial to evaluate the introduction and spread of NIS as well as assess the efficacy of legislation aimed to prevent further introductions. Settlement plates have long been used as a means of studying fouling communities. Many factors such as orientation, movement, and substrate type have been shown to influence the number and type of organisms present in fouling communities, but one key question remains poorly studied: how well do settlement plates represent the established fouling community of a marina, especially regarding NIS? We investigated this question, by examining the sessile invertebrates on both marina structures and settlement plates from three marinas in San Francisco Bay (California, USA). Total species richness, NIS richness, and community composition on settlement plates were found to be similar to those on existing marina floating docks. Our results indicate that settlement plates can provide a sensitive and standardized measure of the NIS richness and composition in fouling communities.

Pile-supported embankment over soft soil for a high-speed line

Abstract: In the construction of the new South Europe Atlantic high-speed line, many embankments have been built on very soft soil. In particular, to access the new bridge constructed above the Dordogne River, a high embankment has been constructed on peat and clay. To minimise the expected settlement and to reduce construction time, a pile-supported embankment (PE) was initially designed based on driven precast concrete piles with a square pile head. A geogrid reinforced piled embankment (GRPE) system was proposed as a ground improvement method to replace the initial choice. To compare the efficiency of the GRPE system and the PE system, a full-scale experimental reinforced embankment was established. The measurements show that the GRPE system shows less settlement and is more stable than the PE solution, and therefore performs at least as well as the PE solution: the settlement is reduced and stabilised, the load is transferred to the piles and the maximum geogrid strain occurs at the end and around the pile head...

Numerical analysis on the mechanical performance of supporting structures and ground settlement characteristics in construction process of subway station built by Pile-Beam-Arch method

Abstract: Pile-Beam-Arch (PBA) method is an effective approach to control the surface settlement induced by excavation to construct the subway station, especially when the station is located in the urban area with dense buildings. Based on the numerical analysis model of practical engineering, the whole construction stages of the subway station built by PBA method are simulated in this paper. The mechanical performance of supporting structures (such as piles, beams, arches, secondary lining and backfill concrete) and surface settlement characteristics during construction are investigated. The results show that the pre-supporting system of piles, beams and arches is formed in the stage of soil excavation under main tunnel arch; Station hall plate and backfill concrete are two key structures to ensure the support stiffness of PBA supporting system. In addition, compared to the bottom-up method, the top-down method for the secondary lining construction can obviously reduce the internal force of supporting structures and the surface settlement. Combined with in-situ monitoring data, three increase stages of surface settlement and the corresponding settlement ratio are gained and the characteristic of surface settlement trough is also analysed. This study is helpful for further understanding the support mechanism of PBA method and the increase law of the ground settlement during the construction of the station built by PBA method.

Application of a Total Station with RDM to Monitor Tunnel Displacement

Abstract: Formulas for tunnel crown settlement and horizontal displacement measurement are presented in this paper according to the theory of tunnel displacement as measured by a total station with t...

Effect of Differential Ballast Settlement on Dynamic Response of Vehicle–Track Coupled Systems

Abstract: An improved vehicle-track coupled dynamics model that takes into account the differential ballast settlement is presented in this paper. Central to this formulation is an iterative method for acqui...

Load-Carrying Mechanism of Vertical Plate Anchors in Sand

Abstract: An experimental study on the load-carrying mechanism of vertical plate anchors is presented and discussed. It was found that, with a shallow anchor, the rupture surface reached the ground surface, leading to a general shear failure, whereas with deeper embedment, the rupture surface was localized around the anchor. Anchors placed close to the ground surface failed in linear rupture but, when embedded within the failure mechanism, were very close to the polar curve of a logarithmic spiral, which, however, tends to be nearly circular for deeper depths of embedment. The size of rupture surface increases with an increase in density of fill soil that mobilizes higher resistance, leading to enhanced anchor capacity. The critical embedment depth beyond which the anchor breakout factor does not change much is found to be approximately 7 times the anchor height for dense soil, whereas it is approximately 5 times the anchor height for loose soil. The anchor when placed below the critical depth, settlement, ...

Prediction of maximum surface settlement caused by earth pressure balance shield tunneling using random forest

Abstract: Due to urbanization and population increase, need for metro tunnels, has been considerably increased in urban areas. Estimating the surface settlement caused by tunnel excavation is an important task especially where the tunnels are excavated in urban areas or beneath important structures. Many models have been established for this purpose by extracting the relationship between the settlement and the factors that influence it. In this paper, Random Forest (RF) is introduced and investigated for the prediction of maximum surface settlement caused by EPB shield tunneling. Various factors that affect this settlement, including geometrical, geological and shield operational parameters were considered. The results of RF model has been compared with the available artificial neural network (ANN) model. It is shown that the proposed RF model provides more accurate results than the ANN model proposed in the literature.

Study on Subgrade Settlement Characteristics After Widening Project of Highway Built on Weak Foundation

Abstract: Generally, the maximum differential settlement appears at the overlapping area of existing and new road pavement after highway widening project. However, lots of longitudinal cracks and other kinds of distresses were found on the existing pavement after the widening project of Guangsan Highway. The field investigation was carried out to find out the reason that the large settlement appeared on existing lanes induced by the weak foundation under the existing lanes, which leaded the cracks observed on the existing pavement. In addition, numerical method was adopted to verify this explanation. The parameter sensitivities were studied to discuss the characteristics of subgrade settlement after the highway widening project. Factors considered include different layouts of cement-fly ash-gravel (CFG) piles, different strengths of CFG piles and different filling materials of new embankment. The results showed that the settlement of pavement became larger when the existing road has weaker foundation. The maximum settlement on the ground surface shifts toward the new embankment when the foundation of existing road has higher strength. The lightweight filling material was proved to have advantage in reducing the settlement of the existing embankment.

Measured short-term subsurface ground displacements from EPBM tunnelling in London Clay

Abstract: Subsurface ground displacements from the construction of the twin-bore Crossrail tunnels in London Clay by earth pressure balance machines (EPBMs) are presented and discussed, complementing a compa...

Soil–structure interaction in a combined pile–raft foundation – a case study

Abstract: The present work explains the use of a piled-raft foundation in a raw materials storage building in South Ba Rịa–Vũng Tau Province of Vietnam. The proposed foundation comprises an 81 m by 55·5 m raft that connects 581 precast hollow concrete piles 20 m long with 400 mm outer diameter. The proposal takes into consideration a specific in situ soil profile and a loading scenario. After the effectiveness of a single bay of the foundation had been checked, the entire foundation system was modelled using finite-element-based geotechnical software to enable a detailed soil–structure interaction analysis. Field pile load test data were used to validate the finite-element model. Various loading conditions, such as all compartments full to all compartments empty, were considered in the analysis. The results of the analyses indicate the importance of the raft in sharing 23–31% of the total vertical load. The results obtained – such as vertical settlement, differential settlement, tilt in the raft and axial load in t...