局部桩筏基础的设计与施工     

Ron Xia  Vladimir Dolezel  L Rak 《地球科学与环境学报》2009,31(2):188-194

以加拿大多伦多市某工程为例,介绍了在复杂地质条件下采用局部桩筏基础(PPRF)的设计及施工问题;探讨了设计PPRF的决定性因素;在保持PPRF设计的完整性前提下,提出了单位沉降量的准则,并用于筏板和桩的设计;计算了PPRF的滑移及转动;最后,采用有效方法对该工程采用的局部桩筏基础进行了计算分析.结果表明,PPRF的设计主要取决于侧向土压力、分布不均的建筑荷载以及地基土的非均匀承载力,工程桩应主要布置在沉降较大的区域,即位于筏板基础承受高压力而土体承载力较低的西北部.探讨局部桩筏基础的设计与施工为该类型工程的基础设计提供了一个新的解决途径.  相似文献   

桩承式高速铁路路基的地震反应特性研究   总被引：1，自引：0，他引：1       下载免费PDF全文

宋永山  高盟  彭晓东  徐晓 《地震工程学报》2021,43(3):644-653

桩承式路基在我国高铁路基中广泛应用,因此,论文建立地震荷载作用下轨道-路基-地基三维数值计算模型,研究地震荷载作用下桩承式路基的地震反应特性,分析桩径、桩长、桩间距、桩身弹性模量等计算参数对路基地震反应的影响,并与自由式路基的地震反应对比.自由式路基地震反应特性表明,地震荷载作用下水平x方向钢轨振动位移幅值最大,是z方...  相似文献   

Isomer specific determination of hexabromocyclododecanes (HBCDs) in small cetaceans from the South China Sea--Levels and temporal variation   总被引：1，自引：0，他引：1  

Isobe T  Ramu K  Kajiwara N  Takahashi S  Lam PK  Jefferson TA  Zhou K  Tanabe S 《Marine pollution bulletin》2007,54(8):1139-1145

A diastereoisomer (alpha, beta, and gamma) specific analytical method for measuring hexabromocyclododecanes (HBCDs) was developed using liquid chromatography-tandem mass spectrometry (LC-MS-MS). The method developed was applied to analyze blubber of small cetaceans to divulge the distribution and temporal variation of HBCDs in the Asian marine environment. HBCDs were detected in all the blubber samples of finless porpoises (Neophocaena phocaenoides) and Indo-Pacific humpback dolphins (Sousa chinensis) collected from the South China Sea during 1990-2001. Concentrations of HBCDs were higher in humpback dolphins (31-380 ng/g lipid) than in finless porpoises (4.7-55 ng/g lipid), which can be attributed to habitat differences. Average concentrations of alpha-HBCD in finless porpoises increased from 9.5 ng/g lipid in 1990 to 35 ng/g lipid in 2000/01. alpha-HBCD was predominant among the three isomers with some exceptions in finless porpoises collected in 1990. This is the first report on HBCDs contamination in marine mammals from Southeast Asia.  相似文献   

From catching to watching: Moving towards quality assurance of whale/dolphin watching tourism in Taiwan     

Chung-Ling Chen 《Marine Policy》2011

Taiwan has shifted from harvesting whales and dolphins to protecting all cetacean species since 1990. Whales and dolphins have become major tourist attractions. With an eye on foreseeable future growth and increasing concerns about environmental impact, service delivery, and educational efficacy, the government seeks to achieve the overall quality assurance of whale/dolphin watching tourism by introducing an ecolabelling program. The aim of this study is to examine this program by analyzing its impact on tour operators and visitors. A survey method was used to assess the impact. The results showed that the program is having a positive impact on operators by seeking environmental sustainability and has brought about educational benefits for visitors, including: site-based knowledge, awareness of marine conservation and reinforcing intentions to perform environmentally responsible behaviors. However, money cost is a major factor discouraging tour operator’s participation, even though ecolabels help to construct an image of responsibility. With potential educational benefits for visitors in mind, the study highlights the need for increasing public awareness of the program, expanding marketing of ecolabelled products, and providing economic incentives for tour operators to engage in ecolabelling.  相似文献   

Finite element simulations of the behavior of piled‐raft foundations using a multiphase model     

Emmanuel Bourgeois  Ghazi Hassen  Patrick de Buhan 《国际地质力学数值与分析法杂志》2013,37(9):1122-1139

Finite element simulations of the behavior of a piled raft foundation have been carried out using a multiphase model conceived as an improved homogenization approach. According to this model, the ground reinforced by a group of piles is treated as a homogeneous continuous medium. In this approach, no specific interface elements are necessary to account for the mechanical interaction between the piles and the ground: this interaction is described by means of two scalar parameters, one stiffness parameter and one which can easily be derived from the maximum ground‐pile friction. The implementation of the model into a finite element code provides an efficient tool for the analysis of the influence of the pile number or length on the settlement and bearing capacity of a square piled raft foundation and of the way the total applied load is shared between the raft and the piles. Results are compared with a standard 3D finite element analysis. The comparison highlights the fact that the proposed approach remains to be improved to account for tip resistance. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

环境激励下高桩码头模态参数识别及损伤诊断     

孙熙平  王元战  赵炳皓 《海洋工程》2013,31(5):62-68

高桩码头在长期使用过程中结构损伤是普遍存在的问题,有效检测结构损伤特别是隐蔽性部位对保证码头安全运营具有重要作用。利用NExT-ERA模态参数识别算法和模态应变能损伤定位原理,编制模态参数识别和损伤诊断程序。通过数值算例分析,验证环境激励下高桩码头排架基于模态参数识别及模态应变能进行损伤诊断的可行性和准确性。研究结果表明:NExT-ERA模态识别方法能较精确识别出高桩码头排架的动力参数;模态应变能变化率作为损伤诊断指标对损伤单元有较强的敏感性,能够识别出高桩码头不同工况下的损伤。  相似文献   

Estimation of the Effect of Lateral Flow on Piled Bridge Abutments in Soft Ground Considering Piled Slabs as a Countermeasure of the Abutments     

Young-Suk Song 《Marine Georesources & Geotechnology》2013,31(1):34-52

The effectiveness of a simple method to estimate the lateral movement of piled bridge abutments due to lateral flow from the safety factor (Fs) of slope stability analysis was studied. This was accomplished through the construction and measurement of actual piled bridge abutments and its backfill, with and without piled slabs as a countermeasure. To do this, a computer program SLOPILE (VER 3.0) considering the lateral earth pressure acting on a row of piled bridge abutment was developed. SLOPILE (VER 3.0) can calculate the slope stability for both planar failure surfaces in infinite slopes and arc failure surfaces based on Fellenius or Bishop simplified methods. SLOPILE (VER 3.0) was utilized to design the piled bridge abutment reinforced by a piled slab at a real site. The piled slab can effectively prevent the lateral flow of soft ground and satisfy not only the safety factor of a slope but also the allowable bearing capacity of piles. To verify the design method, an instrumentation system was adapted. The instrumentation results from a case study clearly showed that the piled slab effectively resisted the lateral movement of a bridge abutment due to placement of backfill. Also, the surcharge loads due to backfill were supported by the piled slab and transmitted to the bedrock through the piled slab.  相似文献   

Distribution,behaviour and photo-identification of Atlantic humpback dolphins Sousa teuszii off Flamingos,Angola     

《African Journal of Marine Science》2013,35(3):319-331

Atlantic humpback dolphins Sousa teuszii are a priority for research due to their restricted geographic range, narrow ecological niche and the paucity of existing information. The distribution and behaviour of S. teuszii off Flamingos, southern Angola, was investigated during summer and winter 2008 using boat- and shore-based surveys. In all, 71 S. teuszii sightings were recorded, ranging from one to eight animals. Sousa teuszii inhabited shallow, nearshore waters throughout the region, with the exception of southern areas adjacent to fishing villages. Small bays, sheltered waters behind reef-breaks and areas off dry river mouths were used for foraging/feeding behaviour, whereas most travelling occurred along exposed coast. Ten individual S. teuszii were photo-identified. Multiple resightings (and absence of unmarked animals) indicate that all individuals present at the time of the surveys were photocaptured, exhibited high site fidelity and had year-round occurrence. Association indices of 0.77-1.0 indicated strong social affiliation between eight individuals, particularly in winter. Off Flamingos, S. teuszii occurs in small numbers and exhibits high site fidelity to a relatively small stretch of nearshore habitat, making the species vulnerable to local extirpation. Wider-scale surveys and development of a management plan are crucial to ensuring the long-term conservation of S. teuszii off Flamingos.  相似文献   

Abundance of the Indo-Pacific bottlenose dolphin Tursiops aduncus off south-west Mauritius     

《African Journal of Marine Science》2013,35(3):293-301

The abundance of Indo-Pacific bottlenose dolphins Tursiops aduncus off the south-west coast of Mauritius was estimated using capture-mark-recapture modelling. Over the past two decades this population has been subjected to ongoing anthropogenic disturbance in the form of extensive coastal development. Furthermore, daily dolphin tourism, which started in 1998, has rapidly increased in intensity. Identification photographs were collected between April 2008 and June 2010 from dolphins occurring along a 30 km length of coast where a dolphin tourism industry is concentrated. A total of 137 groups were encountered over 229 survey days. Over 5 000 photographs were taken, from which 35 individuals were considered to be sufficiently distinctively marked to use in mark-recapture analyses. The majority (85.7%) were seen more than once and resighting frequencies indicated a resident population. Three newborn calves were recorded during the study. Open population models produced abundance estimates of <100 individuals in the population. These results will be used to make recommendations for the conservation and management of this small, resident population, which is a valuable economic resource for the island but is currently under threat from high levels of human activity.  相似文献   

Photo-identification of bottlenose dolphins in the far south of New Zealand indicates a ‘new’, previously unstudied population     

TE Brough  M Guerra  SM Dawson 《新西兰海洋与淡水研究杂志》2013,47(1):150-158

Declines in the abundance of bottlenose dolphins in the Bay of Islands and in Doubtful Sound have contributed to the species being classified as Nationally Endangered in New Zealand waters. Updated information on distribution and abundance nationwide is therefore a high priority. This study presents data from the first photo-identification surveys of Paterson Inlet, Stewart Island, conducted to document bottlenose dolphin presence, abundance and residency. Open-population mark-recapture models indicate that 18 (95%CI = 15–20) dolphins regularly use Paterson Inlet. Photo-identification of dolphins from unknown populations during two chance encounters in Otago Harbour and Dusky Sound included 11 individuals previously identified at Stewart Island. These results indicate that dolphins found regularly at Stewart Island are part of a larger, wide ranging southern population with a minimum population abundance of 92 (95%CI = 80–111) individuals.  相似文献