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91.
Plate anchors are extensively used in civil engineering constructions as they provide an economical alternative to gravity and other embedded anchors. The rate of loading is one of the important factors that affects the magnitude of soil resistance as well as soil suction force. This article outlines the effect of pullout rate on uplift behavior of plate anchors (70 mm diameter) buried in soft saturated clay by varying the pullout rate from 1.4 mm/min to 21.0 mm/min. The variation of breakout force and suction force with embedment depth and rate of pull are presented. A correlation between the rate of increase of undrained strength of clay and anchor capacity with rate of strain has been established. Finally an empirical equation has been proposed that includes the rate of pull in the estimation of breakout capacity of anchors. 相似文献
92.
Helical piles are structural deep foundation elements, which can be categorized as torque-driven piles without any limitations to implement in marine situations. Different methods are used to predict the axial capacity of helical piles, such as static analysis, but have some limitation for this type of piles on marine conditions. In situ testing methods as supplement of static analysis have been rarely used for helical piles. In geotechnical engineering practice, the most common in situ tests particularly applicable for coastal or offshore site investigation are cone penetration test (CPT) and piezocone penetration test (CPTu). The CPT is simple, repeatable, and prepares the continuous records of soil layers. In this paper, a data bank has been compiled by collecting the results of static pile load tests on thirty-seven helical piles in ten different sites including CPT or CPTu data. Axial capacities of thirty-seven helical piles in different sites were predicted by direct CPT methods and static analysis. Accuracy estimation of ten direct CPT methods to predict the axial capacity of helical piles was investigated in this study. Comparisons have been made among predicted values and measured capacity from the pile load tests. Results indicated that the recently developed methods such as NGI-05 (2005), ICP-05 (2005), and UWA-05 (2005) predicted axial capacity of helical piles more accurately than the other methods such as Meyerhof (1983), Schmertmann (1978), Dutch (1979), LCPC (1982), or Unicone (1997). However, more investigations are required to establish better correlation between CPT data and axial capacity of helical piles. 相似文献
93.
A series of model tests were performed on steel- and Perspex-made suction caissons in saturated dense marine sand to explore installation and extraction behaviors. The extractions of the caisson were conducted by applying monotonic loading or by pumping water into the caisson. Responses of suction caissons to pullout rates, aspect ratios, and extraction manners were examined. Test results show that a cone-shaped subsidence region occurs around the suction caisson during the suction-assisted installation. The pullout bearing capacity of the suction caisson in sand is dominated by the loading rate and the loading manner. For the suction caisson subjected to monotonic loading, the maximum bearing capacity is reached at the pullout rate of about 20.0?mm/s. The mobilized vertical displacement corresponding to the pullout capacity increases with increasing the pullout rate. The passive suction beneath the suction caisson lid reaches the maximum value when the pullout bearing capacity is mobilized. In addition, during the suction caisson extracted by pumping water into the caisson, the maximum pore water pressure in the caisson is obtained under the displacement of approximately 0.04 times the caisson diameter. The absolute values of the maximum pore water pressures for the suction caissons approximately equal those of the maximum vertical resistances at the monotonic pullout rate of 5 mm/s. When the vertical displacements of the suction caissons with the aspect ratio of 1.0 and 2.0 reach 0.92 and 1.77 times the caisson diameter, respectively, the seepage failure occurs around the caissons. Using a scaling method, the test results can be used to predict the time length required for the prototype suction caisson to be extracted from the seabed. 相似文献
94.
Yu Xiaodong Yan Shuwang Sun Wanhe
Postgraduate Student Tianjin University Tianjin Professor Tianjin University Tianjin Senior Engineer Tianjin Port Engineering Institute Tianjin 《中国海洋工程》1997,(2)
At pesent,it is very popular to estimate pile bearing capacity by use of empirical formula andphysical indexes of soil provided in the design codes for civil construction in China.This paper attempts toapply mechanical indexes of soil and semi-empirical formulas,which are based on soil mechanical theoriesand were summarized and presented by Meyerhof in 1976,to calculate the axial pile bearing capacity.Lo-ading test results of 24 single piles in Tianjin area have been collected and compared with the proposed cal-ulation approach. 相似文献
95.
96.
Abstract The design and construction of a special-purpose laboratory catchment and rainfall simulator is described. The equipment consists of a soil catchment area that can be inclined at various angles. Additional instrumentation then measures the flow of water across the surface of, and through, the soil bed. Precipitation is provided by a unit that simulates rainfall at particular rates with uniform distribution. The equipment was used to examine infiltration, runoff and other hydrological properties of a number of soils under different rainfall intensities and with different catchment slopes. Correlations were obtained for these variables. 相似文献
97.
江苏省环太湖地区快速城市化和工业化加剧饮用水危机,整合研究水源地、供水、用水、排污处理和技术5个方面对于支撑该地区可持续发展的适应能力,对揭示饮用水供需关系、存在问题、部门协调与综合决策等具有现实意义.本文以构建5个子系统适应能力指标体系为主线,通过分指数与综合指数评价的运算,得出研究地区饮用水系统适应能力等级水平、地域分异特征及影响因素分析;针对各子系统存在问题,提出维护和提升适应能力的对策措施.研究表明,适应能力较强的地区占总面积29.1%,其5个子系统适应能力均较强.适应能力中等地区占41.2%,一类是各子系统适应能力基本均等,另一类是排污处理子系统适应能力较强,但用水子系统得分较低.适应能力较差地区占29.7%,主要是技术子系统分值低,其它子系统适应能力处于中等偏下.因此需加大对各子系统适应能力的调控与提升. 相似文献
98.
99.
进行了12个钢管约束混凝土压弯构件在往复荷载作用下的荷载-变形滞回性能的实验研究,包括6个圆试件和6个方试件。考察的主要参数是构件的轴压比。通过实验观察了这类构件在往复荷载作用下的破坏模态并分析了其荷载-变形滞回曲线的特点以及刚度退化规律,同时对钢管约束混凝土压弯构件极限承载力和抗弯刚度计算方法进行了初步探讨。 相似文献
100.