A novel strut-free retaining wall system for deep excavation in soft clay: numerical study     

Lim  Aswin  Ou  Chang-Yu  Hsieh  Pio-Go 《Acta Geotechnica》2020,15(6):1557-1576

This paper presents a novel strut-free earth retaining wall system for excavation in soft clay, referred to as the rigid and fixed diaphragm (RFD) wall retaining system. The RFD system is comprised of four main structures—diaphragm walls, rib-walls, cross walls, and buttress walls—and a complementary structure—the cap-slab. The characteristics of the RFD system are: (1) the formation of a continuous earth retaining wall by constructing diaphragm walls along the circumference of the excavated zone; (2) the formation of a rigid and fixed retaining wall system by a series of rib-walls and cross walls; and (3) the formation of a rigid retaining wall by buttress walls and the cap-slab. Furthermore, the performance and mechanisms of the RFD system were investigated carefully through three-dimensional finite element analyses. The results demonstrated that the system stiffness of the RFD system was a major factor controlling deformations induced by excavation. Moreover, the excavation geometry determined the dimension of each component of the RFD system.

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Statistical modeling for the mitigation of GPS multipath delays from day-to-day range measurements   总被引：1，自引：0，他引：1  

Joz Wu  Chi-Hsiu Hsieh 《Journal of Geodesy》2010,84(4):223-232

Based on a least-squares model for double-difference GPS pseudoranges and carrier-phases, measurement residuals expressed in time series during an observation session are positively correlated between one sidereal day and the preceding days. As a result of the satellite’s period, the phenomenon, which takes place at a user receiving site, is attributed to multipath interference. Examples from a weekly measurement dataset of control baselines are shown, where the known end-point coordinates also serve as a benchmark for assessing positioning accuracy. The system of error equations for mixed-model adjustment is divided into two subsystems. One set of the error equations is related to the real range measurements, while the other involves the pseudo-observation with an empirical sample variance. According to the existing correlation between day-to-day residual estimates, a multipath-mitigating algorithm is proven to improve the accuracy of the GPS height determination by at least 40%. It is also found that the algorithm depends on a variance-component estimator that adaptively scales an error covariance matrix for both the real range and empirical delay measurements.  相似文献   

Distribution of erosion across bedrock channels     

Jens M. Turowski  Niels Hovius  Hsieh Meng‐Long  Dimitri Lague  Chen Men‐Chiang 《地球表面变化过程与地形》2008,33(3):353-363

Lateral erosion in bedrock rivers is an important control on the shape of channel cross‐sections, and the coupling of channels and hillslopes. Recent observations link lateral erosion to the variability of flow. We propose two mechanisms to explain this. One is based on changing shear stress distributions within the channel with varying flood level, the other on the competition between cover and tool effects in fluvial bedrock erosion. We assess these processes for the Liwu River, Taiwan, and conclude that cover and tool effects dominate the partitioning of lateral and vertical erosion in this case. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Parameter identification for on‐line model updating in hybrid simulations using a gradient‐based method          下载免费PDF全文

Ming‐Chieh Chuang  Shang‐Hsien Hsieh  Keh‐Chyuan Tsai  Chao‐Hsien Li  Kung‐Juin Wang  An‐Chien Wu 《地震工程与结构动力学》2018,47(2):269-293

To improve the efficiency of model fitting, parameter identification techniques have been actively investigated. Recently, the applications of parameter identification migrated from off‐line model fitting to on‐line model updating. The objective of this study is to develop a gradient‐based method for model updating to advance hybrid simulation also called hybrid test. A novel modification of the proposed method, which can reduce the number of design variables to improve the identification efficiency, is illustrated in detail. To investigate the model updating, simulated hybrid tests were conducted with a 5‐story steel frame equipped with buckling‐restrained braces (BRBs) utilized in the shaking table tests conducted in E‐Defense in Japan in 2009. The calibrated analytical model that was verified with the test results can serve as the reference model. In the simulated hybrid tests, the physical BRB substructure is numerically simulated by utilizing a truss element with the 2‐surface model identical to the part of the reference model. Such numerical verification allows simulation of measurement errors for investigation on the performance of the proposed method. Moreover, the feasibility of sharing the identified parameter values, which were obtained from the physical substructure responses, with the relevant numerical models is also verified with the artificial component responses derived from the physical experiments.  相似文献   

Characterization of horseshoe vortex in a developing scour hole at a cylindrical bridge pier   总被引：1，自引：0，他引：1  

Dawei Guan  Yee-Meng Chiew  Maoxing Wei  Shih-Chun Hsieh 《国际泥沙研究》2019,34(2):118-124

Since local scour at bridge piers in rivers and estuaries is a major cause of bridge failure, estimation of the maximum local scour depth is of great importance to hydraulic and coastal engineers. Although numerous studies that focus on scour-depth prediction have been done and published, understanding of the flow and turbulence characteristics of the horseshoe vortex that drives the scour mechanism in a developing scour hole still is immature. This study aims to quantify the detailed turbulent flow field in a developing clear-water scour hole at a circular pier using Particle Image Velocimetry (PIV). The distributions of velocity fields, turbulence intensities, and Reynolds shear stresses of the horseshoe vortex that form in front of the pier at different scour stages (t=0, 0.5, 1, 12, 24, and 48 h) are presented in this paper. During scour development, the horseshoe vortex system was found to evolve from one initially small vortex to three vortices. The strength and size of the main vortex are found to increase with increasing scour depth. The regions of both the maximum turbulence intensity and Reynolds shear stress are found to form at a location upstream of the main vortex, where the large turbulent eddies have the highest possibility of occurrence. Results from this study not only provide new insight into the complex flow-sediment interaction at bridge piers, but also provide valuable experimental databases for advanced numerical simulations.  相似文献   

Determination of mechanisms and hydrogeological environments of Gangxianlane landslides using geoelectrical and geological data in central Taiwan   总被引：1，自引：1，他引：0  

Cheng-Chao Lee  Li-Sheng Zeng  Chin-Hsien Hsieh  Chun-Yi Yu  Sheng-Hsiung Hsieh 《Environmental Earth Sciences》2012,66(6):1641-1651

Electrical resistivity tomography (ERT), single-point-resistance logging with time-lapse, and geological and groundwater level data, are utilized to determine the mechanism of, and a hydrogeological model of, the Gangxianlane landslide in the west-central part of Taiwan. The rock surface and geometry of the colluviums were found by integrating ERT and borehole data. The iso-resistivity line in the bedrock broadly followed the bedding plane, indicating that the contribution of lithology to resistivity exceeds that of groundwater. The results of single-point-resistance logging with time-lapse and borehole data reveal that the bedrock has low permeability, which is associated with poorly developed joints and fractures. The fine grain content part (including the clayey layer), almost parallel to the bedding plane of the bedrock and between the colluvium and the bedrock in the upper part of the landslide, served as the slip surface and is believed to have been recently produced. It can block and retain water in the colluviums. Accordingly, this slip surface has the potential to re-slip in the future. Another slope failure involved rock collapse by a well-developed open release joint close to the Huoshaoping Terrace. It is also related to groundwater flow over a large gradient from the Huoshaoping Terrace. It is a key to determining whether this landslide will expand in the future.  相似文献   

A new weir surface repair layer with shock absorbing cushion design     

Tse-Shan Hsu  Yi-Lang Hsieh 《地震工程与工程振动(英文版)》2013,12(3):487-496

A shock absorbing cushion has never been introduced into any traditional weir surface repair layer design.However,shocks induced by high discharge with heavy sediment can easily produce brittle fracture and peeling over a weir surface repair layer as it is impacted by floods accompanied by particles of different sizes.In this study,transcending traditional designs,the authors developed a composite unit designed with a shock absorbing cushion that has performed well during field tests,proving that the weir body can be effectively protected even if the composite units are directly laid on a severely uneven weir surface repair layer.  相似文献   

The mechanical behaviour and design concerns for a hybrid reinforced earth embankment built in limited width adjacent to a slope     

Chia-Cheng Fan  Chih-Chung Hsieh 《Computers and Geotechnics》2011

This paper aims to investigate the mechanical behaviour of a hybrid reinforced earth embankment built in limited width adjacent to a slope. This embankment system incorporates reinforced earth embankments with soil nails, installed in the existing ground. Soil nails work to provide additional resisting forces to stabilize the embankment which may be unstable due to insufficient reinforcement length. Nail forces developed in the hybrid reinforced earth embankment with various geometric conditions in the fill space are analyzed. The FE method is used to simulate the construction of the hybrid reinforced earth embankment. Influence of reinforcement length, reinforcement stiffness, and slope gradient on the nail forces developed following the construction is analyzed and discussed. Additionally, design concerns for the hybrid reinforced earth embankment system are also studied. Simple charts for estimating the maximum nail force mobilized at back of the hybrid reinforced earth embankment are established in this research and can be helpful in the design of the soil nails in the system.  相似文献   

Monsoon-driven succession of the larval fish assemblage in the East China Sea shelf waters off northern Taiwan   总被引：2，自引：0，他引：2  

Hung-Yen Hsieh  Wen-Tseng Lo  Long-Jing Wu  Dong-Chung Liu  Wei-Cheng Su 《Journal of Oceanography》2011,67(2):159-172

The seasonal variation in the larval fish community related to the hydrography in the East China Sea (ECS) off northern Taiwan was studied from February to November 2004. Hydrographic conditions in the southern ECS are strongly influenced by the different water masses due to the seasonal monsoon system. A total of 173 taxa of larval fish belonging to 68 families and 105 genera were identified during the study period. The highest abundance of larval fish was recorded in winter, a moderate abundance was seen in late spring and summer, and the lowest abundance in autumn. Significantly higher abundances were usually found in the mixing zone than in ECS and the Kuroshio Current, and the number of species of larval fish was greater during the warm period than during the cold period. The larval fish fauna in the southern ECS is a mixture of endemic and exotic species; the latter come from the coastal waters of mainland China when the northeasterly monsoon prevails, from the South China Sea during the southwesterly monsoon, and from the Kuroshio waters year-round. The succession of water masses induced by the monsoon systems and the high nutrient levels caused by frontal turbulence and topographic upwelling may determine the distributions of larval fish in terms of abundance and composition.  相似文献   

The identified origin of a linear slope near Chi–Chi earthquake rupture combining 2D, 3D resistivity image profiling and geological data     

Cheng-Chao Lee  Louis Loung-Yie Tsai  Chieh-Hou Yang  Kuo-Liang Wen  Zi-Bin Wang  Zhi-Hsian Hsieh  Hsing-Chang Liu 《Environmental Geology》2009,58(7):1397-1406

A slope on the west border of the foothill near 921 surface rupture (caused by the 1999 Chi-Chi earthquake) in central Taiwan shows distinctive topographic expression that was prone to be considered as a fault scarp formed by a preexisting active fault. The 2D and 3D resistivity images clearly delineate rock surfaces which show steep, deep, gentle, and subvertical displacement beneath the slope, the toe of slope, the non-lateritic terrace, and 921 surface rupture, respectively, which can be attributed to the significant contrast of resistivity between gravel and rock. The horizontal sand bed and clast-supported gravel were deposited in a fluvial environment, whereas wedge-shaped gravel and colluvium were scarp-induced colluvial deposits in the trench profile. The layers shown in the depth of excavation, except for rock, has no offset or disturbance by fault ever since at least 2,480 ± 50 year B.P., based on carbon 14 dating of charcoal sample at the bottom of trench profile. According to information from two boreholes close to the slope, an over 20-m-thick marker bed with transported shell fragments, was found for correlation. This correlation further implies the slope was not formed by fault. On the other hand, two boreholes which are far from the slope and located on the flat non-lateritic terrace frequently show fractured and sheared features. By comparison, the locations around these two boreholes indicate a reverse fault or faults that occurred before the deposition of gravel. Later on, the paleostream was developed along the foot of fault scarp that was subjected to erosion and led to subsequent retrogression or retreat of the slope. Consequently, the incision of paleostream is believed to be responsible for the high relief of rock surface around the slope. Furthermore, from resistivity and borehole data, the rock surface underlying terrace is gentle where no faults occur after the deposition of gravel. The result of RIP crossing the 921 surface rupture displays about 10 m difference in elevation of rock surface on both sides, which is greater than that of 3–4 m caused by Chi-Chi earthquake. This indicates that the 921 surface rupture is a preexisting thrust fault that resulted from several thrusting events since terrace gravel was deposited. So it is not necessary to establish an extra restricted zone for construction in study area, except close to the 921 surface rupture.  相似文献