Development of Prebored Screw Pile Method and Evaluation of Its Bearing Characteristics     

Chung-Won Lee  Sung-Yong Park 《Marine Georesources & Geotechnology》2016,34(1):42-56

The pile-driving method produces considerable noise and vibrations. Hence, an auger-drilled pile method was developed as a low-noise and -vibration substitute. However, this method does not guarantee the bearing capacity of the pile unless some amount of pile-driving is performed. Therefore, the noise and vibration problems cannot be completely solved. In this study, a prebored screw pile method is proposed to solve these problems. In this method, piles are constructed by the rotary penetration of a screw pile into a prebored hole filled with some cement milk and whose diameter is smaller than that of the screw pile. To determine the shape of the screw pile, laboratory tests with model screw piles were conducted. Also, field load tests were conducted on an actual screw pile fabricated based on the laboratory test result and on a smooth-surfaced pile. In addition, the behavior of the screw pile was estimated by using three-dimensional finite element analysis. The results of the field load test and the numerical simulation showed that the ultimate bearing capacity and the unit skin friction of the screw pile are very superior to those of the smooth-surfaced pile and the cement milk is an important factor in the prebored screw pile method.  相似文献   

Helical probe tests in residual soils of the Appalachian Piedmont     

Shehab S. Agaiby  Zhongkun Ouyang  Paul W. Mayne 《Geomechanics and Geoengineering》2018,13(3):217-225

Helical probe tests (HPT) are a quick and economical means for manual field testing of soils to depths of 1.5 m with readings taken at 0.15-m intervals in only 10 min. The equipment is lightweight (only 2 kg) and thus amenable to deploy on initial site reconnaissance explorations, shallow pavement projects, earth retention walls, and/or compaction of fills. Although suitable for use in a variety of geomaterials: sands, silts, clays, and mixed soils, the specific application to residual fine sandy silts and silty fine sands of the Appalachian Piedmont and Blue Ridge geologic provinces is shown here. Existing relationships for converting the measured HPT torque reading to equivalent cone penetration testing (CPT) tip resistances are reviewed, as well as other trends.  相似文献   

基于微纳气泡示踪的拖曳法ADCP流速测试   总被引：1，自引：0，他引：1  

韩继伟  邵军  符伟杰  赵士伟  毛春雷  房照娟 《水文》2021,41(2):63-68

声学多普勒剖面流速仪(ADCP)设备在水文领域保有量大、应用广,但如何对其进行量值溯源,确保现场测量数据准确可靠是用户非常关注的问题。分析ADCP的测试现状,阐述ADCP的6个测试参数,分析出流速测试是核心;利用微纳气泡作为示踪粒子,尝试解决静止水体无反射粒子的问题,为ADCP流速测试提供支撑;以TRDI的WHR600-1型ADCP为例,说明ADCP流速测试过程和试验数据处理方法。得出微纳米气泡是ADCP拖曳水槽水跟踪测试较好的示踪物质,进而实现ADCP水跟踪流速测试。为拖曳水槽ADCP测试改造建设提供技术思路,并给出实验室测试建议。  相似文献   

免共振沉桩过程对地表振动影响的FLAC3D数值模拟     

魏家斌  王卫东  吴江斌 《吉林大学学报(地球科学版)》2021,51(5):1514-1522

为研究免共振沉桩过程对地表振动影响,采用密度放大法以消除模型桩弹性模量过大对计算效率的影响,在有限差分软件FLAC^3D中建立了相应的连续振动沉桩模型,并和文献中的现场测试结果进行了比较,分析了激振力幅值和振动频率这两个施工参数对地表振动响应的影响。结果表明：密度放大法可有效提高数值模拟的计算效率,模拟沉桩7.0倍桩径（4.9 m）所需计算时间约为12.0 h,数值结果较好地模拟了现场测试中免共振沉桩的地表振动影响;激振力幅值和振动频率均主要对近场（水平距离为5.0倍桩径范围内）的地表振动有明显影响;临界沉桩深度与地表振动影响峰值相对应,该深度随水平距离先增大后趋于稳定;激振力幅值对临界沉桩深度的改变不明显,振动频率对远场临界沉桩深度则有较明显影响。  相似文献   

A generalized conditional intensity measure approach and holistic ground‐motion selection     

Brendon A. Bradley 《地震工程与结构动力学》2010,39(12):1321-1342

A generalized conditional intensity measure (GCIM) approach is proposed for use in the holistic selection of ground motions for any form of seismic response analysis. The essence of the method is the construction of the multivariate distribution of any set of ground‐motion intensity measures conditioned on the occurrence of a specific ground‐motion intensity measure (commonly obtained from probabilistic seismic hazard analysis). The approach therefore allows any number of ground‐motion intensity measures identified as important in a particular seismic response problem to be considered. A holistic method of ground‐motion selection is also proposed based on the statistical comparison, for each intensity measure, of the empirical distribution of the ground‐motion suite with the ‘target’ GCIM distribution. A simple procedure to estimate the magnitude of potential bias in the results of seismic response analyses when the ground‐motion suite does not conform to the GCIM distribution is also demonstrated. The combination of these three features of the approach make it entirely holistic in that: any level of complexity in ground‐motion selection for any seismic response analysis can be exercised; users explicitly understand the simplifications made in the selected suite of ground motions; and an approximate estimate of any bias associated with such simplifications is obtained. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Internal erosion of chemically reinforced granular materials: a mathematical modeling approach     

Tony Khalil  Nadia Saiyouri  Bogdan Muresan  Pierre‐Yves Hicher 《国际地质力学数值与分析法杂志》2013,37(5):491-502

Internal erosion (IE) affects the stability of natural and reinforced materials by causing instability within their granular structure. The dislodgement and transport of eroded particles affect both the particulate concentration of eroding fluid and the pore network of eroded material. In this study, we examined these modifications using a transport model with a finite element code. First, IE tests on chemically reinforced sand columns were performed to obtain information about eroded material loss of mass, particulate concentration of effluent, porosity and permeability modifications, and existing IE stages. Second, based on experimental results, a mathematical one‐dimensional model has been formulated to monitor the evolution and spatial distribution of erodible solids, fluidized particles, porosity, permeability, and seepage stresses. The model consists of a set of coupled nonlinear differential equations solved in sequence. It provides valuable information about the extent and the dynamics of structural changes, which can be used to estimate an IE time for the hydraulic work to reach failure. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

A comparison of fibre‐optic distributed temperature sensing to traditional methods of evaluating groundwater inflow to streams     

Martin A. Briggs  Laura K. Lautz  Jeffrey M. McKenzie 《水文研究》2012,26(9):1277-1290

There are several methods for determining the spatial distribution and magnitude of groundwater inputs to streams. We compared the results of conventional methods [dye dilution gauging, acoustic Doppler velocimeter (ADV) differential gauging, and geochemical end‐member mixing] to distributed temperature sensing (DTS) using a fibre‐optic cable installed along 900 m of Ninemile Creek in Syracuse, New York, USA, during low‐flow conditions (discharge of 1·4 m³ s^?1). With the exception of differential gauging, all methods identified a focused, contaminated groundwater inflow and produced similar groundwater discharge estimates for that point, with a mean of 66·8 l s^?1 between all methods although the precision of these estimates varied. ADV discharge measurement accuracy was reduced by non‐ideal conditions and failed to identify, much less quantify, the modest groundwater input, which was only 5% of total stream flow. These results indicate ambient tracers, such as heat and geochemical mixing, can yield spatially and quantitatively refined estimates of relatively modest groundwater inflow even in large rivers. DTS heat tracing, in particular, provided the finest spatial characterization of groundwater inflow, and may be more universally applicable than geochemical methods, for which a distinct and consistent groundwater end member may be more difficult to identify. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

地热异常的水槽模型实验     

魏文博  魏新发 《地球科学》1988,(3)

作为地球物理场的一个分支,地温场在理论和应用研究方面与其它地球物理场一样,也主要是依靠数学方法和物理模型实验的方法来进行的。本文讨论了地热异常水槽模型实验的理论原理;介绍了实验方法技术、实验结果和实际应用效果。  相似文献   

Laboratory simulation of natural leaching processes of eastern USA oil shale     

M. Shirav  T. L. Robl 《Environmental Geology》1993,22(1):88-94

Raw and retorted spent oil shales from Kentucky, as well as soil and overburden materials, were subjected to laboratory and field leaching tests. Standard batch leaching tests grossly undervalue the amount of dissolved ions as measured in the field, being too brief to enable slow reactions of the mineral matrix, such as hydrolysis and oxidation of sulfides or reactions of acidic leachates with soluble components of the clays. Laboratory column tests, devised to closely simulate natural leaching processes, achieved concentration levels and elemental release patterns similar to those found in field tests. The column tests provide a reliable means to assess the leachability of metals in these materials.  相似文献   

The impact of the Laacher See Volcano (11 000 yr B.P.) on terrestrial vegetation and diatoms     

H. J. B. Birks  A. F. Lotter 《Journal of Paleolimnology》1994,11(3):313-322

Late-glacial lake sediments containing the Laacher See Tephra (LST, 11 000 yr B.P.) have been analyzed for their pollen and diatom content at three sites at varying distances from the volcano and on different bedrock geologies. The aim was to test the null hypothesis that this major volcanic eruption had no effect on terrestrial pollen or aquatic diatom assemblages. The pollen spectra at all sites show a short-lived increase in grass pollen following the LST. Partial redundancy analysis and associated Monte Carlo permutation tests suggest, however, that the LST had no statistically significant effect at two sites but it had a statistically significant impact on the pollen assemblages at the site nearest (60 km) to the volcano.The diatom assemblages at the three sites changed individualistically after the LST deposition, with increases inAchnanthes minutissima at one site, an expansion ofAulacoseira species at another, and an increase ofAsterionella formosa andFragilaria brevistriata at the third site. Partial redundancy analysis and associated permutation tests suggest a statistically significant change in diatoms in relation to the LST and associated changes in sediment lithology at the one site situated on acidic bedrock. No significant impacts were found at the sites on volcanic or calcareous rocks. Due to the interaction between tephra and sediment lithology, it is not possible to conclude if the statistically significant diatom changes were a direct result of the LST deposition or an indirect result of lithological changes following LST deposition.This is the first paper in a series of papers published in this issue on high-resolution paleolimnology. These papers were presented at the Sixth International Paeolimnology Symposium held 19–21 April, 1993 at the Australian National University, Canberra, Australia. Dr A. F. Lotter and Dr. M. Sturm served as guest editors for these papers.  相似文献