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通过在钻孔灌注桩中预埋注浆管,对地基土进行注浆加固,提高钻孔灌注桩承载力的两个工程实例,分析了地基土及注浆参数对加固效果的影响,并通过成本比较肯定了该工艺技术的经济适用性。 相似文献
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A method of analysis for the uplift capacity of pile anchors in cohesionless soil is proposed using Kötter’s equation that facilitates computation of the distribution of soil reaction on the axis-symmetric failure surface, which is assumed to be the frustum of a cone with a characteristic angle of inclination with the pile–soil interface. A closed-form solution for the uplift capacity is obtained with no requirement of any charts or tables. Empirical relations using available literature are proposed for expressing critical embedment ratio and computation of net uplift capacity. The results are compared with a set of experimental data for 28 cases, ranging from loose to dense cohesionless soil up to maximum embedment ratio of 40, vis-à-vis available theoretical solutions. The proposed method leads to the predictions that are in good agreement with the experimental results. It further demonstrates the successful application of Kötter’s equation in the estimation of uplift capacity of pile anchors. 相似文献
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J. Amanollahi C. Tzanis A. M. Abdullah M. F. Ramli S. Pirasteh 《International Journal of Environmental Science and Technology》2013,10(6):1245-1254
Particulate matter concentration and assessment of its movement pattern is crucial in air pollution studies. However, no study has been conducted to determine the PM10 concentration using atmospheric correction of thermal band by temperature of nearest dark pixels group (TNDPG) of this band. For that purpose, 16 Landsat Enhanced Thematic Mapper plus ETM+ images for Sanandaj and Tehran in Iran were utilized to determine the amount of PM10 concentration in the air. Thermal infrared (band 6) of all images was also used to determine the ground station temperature (GST b6) and temperature of nearest dark pixels group. Based on atmospheric correction of images using temperature retrieval from Landsat ETM+, three empirical models were established. Non-linear correlation coefficient with polynomial equation was used to analyze the correlations between particulate matter concentration and the ground station temperature for the three models. Similar analyses were also undertaken for three stations in Klang Valley, Malaysia, using 11 Landsat ETM+ images to show the effectiveness of the model in different region. The data analysis indicated a good correlation coefficient R = 0.89 and R = 0.91 between the trend of the result of temperature of nearest dark pixels group b6 ? (GST b6 ? GST) model and the trend of PM10 concentration in Iran and Malaysia, respectively. This study reveals the applicability of the thermal band of Landsat TM and ETM+ to determine the PM10 concentration over large areas. 相似文献
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人工挖孔桩桩端土承载力的确定 总被引:2,自引:0,他引:2
城市建设中高层建筑越来越多.基础大多采用单桩承栽能力很高的人工挖孔灌注桩。既保证桩基工程的安全.又能节省工程造价.桩端土承栽力参数的确定在基础工程设计中是十分重要的。本文提出了应用深层平板栽荷试验方法能够较准确的提供桩端土承栽力参数.并在不同地质条件下进行了试验.积累了本地区的一些经验;同时认为在桩端土为中粗砂、泥岩时,应用效果很好;桩端土为粘性土时,应用效果较差。 相似文献
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土体水平位移对邻近既有桩基承载性状影响分析 总被引:1,自引:0,他引:1
城市建设中经常会遇到由于堆载或基坑开挖所引起的土体水平位移现象,土体水平位移的作用会使邻近建筑物的桩基础产生附加内力或变形,并可能导致邻近桩基的破坏而发生工程事故。针对此类问题,基于Winkler地基模型以及桩-土变形协调条件,建立单桩水平位移控制方程,根据内力与位移的微分关系,采用两阶段方法进行求解。结合典型的工程事故,通过参数分析,研究土体水平位移对邻近桩基承载性状的影响程度。分析表明,基坑工程围护墙体的稳定和开挖深度对邻近桩基的安全有着重要影响,并提出了近期发生在上海的某小高层楼房整体倒覆事故的一种可能原因。 相似文献
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成层土中倾斜荷载作用下桩承载力有限元分析 总被引:6,自引:1,他引:6
利用有限元方法对现场单桩水平载荷试验进行模拟,在此基础上,分析了成层土中桩在倾斜荷载作用下其竖向分量的有利作用和横向土抗力分布特点。计算结果表明,在地面下一定范围内,倾斜荷载作用下的桩侧摩阻力比水平荷载作用下的桩侧摩阻力大。在土层分界处土抗力分布有明显的跳跃。达到一定深度后,横向土抗力主要是静止土压力,而由荷载引起的横向土抗力很小。承台能有效减小土体及桩的水平位移。模拟的灌注桩和钢管桩桩顶在地面以上的自由长度较小,竖向分量由于桩身挠曲变形而产生的P-Δ效应较小,所以就算例中的灌注桩和钢管桩而言,荷载倾斜度不大时,荷载竖向分量提高了桩的侧阻并由此增大桩侧土竖向应力,对桩水平承载力总体上起到了有利的作用。 相似文献
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王兴龙 《水文地质工程地质》2000,27(4):51-54
通过改变水泥掺量及控制搅拌程度设计多个试验桩,再分别测试其承载力及水泥土强度值,通过对测试数据的分析可得到,在水参量达到一定程度时,搅拌程度是至关重要的,这个结论对搅拌桩工程施工具有较大的实用意义。 相似文献
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粘弹性地基中有限长桩横向受迫振动问题解析解 总被引:5,自引:1,他引:5
基于动力Winkler模型(BDWF)对粘弹性地基中有限长桩的动力响应进行求解,得到了其在桩顶受水平循环荷载作用下的简单形式的时域解析解。通过迭加原理得到了半正弦激振条件下的瞬态解析解,经过简单的数学运算得到了桩头动力阻抗系数。通过对稳态激振时幅频曲线和相频曲线的分析,讨论了桩侧土阻尼系数和刚度系数对共振频率和共振峰值的影响规律。并讨论了桩底边界条件对水平动力响应的影响。本文为单桩的动力分析提供了一种简单的解析分析方法,可为工程设计提供初步参考。 相似文献
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We perform a combined stochastic-deterministic analysis of local site response using two computer codes, an equivalent linear analysis program SHAKE and a fully nonlinear finite element code SPECTRA. Our goal is to compare the relative sensitivity of the two codes to statistical variations in soil properties. For the case studies, we re-analyze two ground motion records in Lotung, Taiwan, and one ground motion record in Gilroy, California, utilizing the recorded ground motions at the site deterministically as input into the two codes while treating the uncertain soil parameters as random variables. We then obtain empirical cumulative distribution functions of the Arias intensity and acceleration spectrum intensity, two measures of cumulative damage, to compare the relative sensitivity of the two codes to variations in model parameters. We show that the two codes exhibit comparable sensitivities to statistical parameter variations, indicating that even in the presence of fluctuations in the soil parameter values it is possible to pursue a fully nonlinear site response analysis with SPECTRA and benefit from its superior accuracy. 相似文献
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We investigate the time dependence of the number of deaths reported through Internet after earthquakes and/or earthquake-generated
tsunami. An approximate relation N(t) = N
0 [1 − exp(−αt)] is used to describe such temporal variation, in which N(t) is the number of deaths reported at time t, N
0 is the final number of deaths, and α is the coefficient reflecting the rescue process. We considered 12 earthquake cases since 2001 using the information from
the web, which shows that the N-t relation approximates the data, and the logarithm of α is reversely proportional to the magnitude of earthquake, albeit with significant uncertainties. Quick and rough estimate
of the final death toll can be made using this simple and approximate relation, with the empirical α-M relation as a reference. For the 12 cases under consideration, quick and rough estimate of fatalities can be obtained 2 days
after the earthquake, fitting the real situation in the order of magnitudes. Although being very rough, this estimate can
assist the emergency decision-making and can be revised as time lapses. When more and more data becomes available, curve fitting
can provide both N
0 and α at the same time. The method is tested against the data of the recent Yushu earthquake on April 14, 2010. 相似文献
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Pedotransfer functions to estimate soil water content at field capacity and permanent wilting point in hot Arid Western India 总被引:1,自引:0,他引:1
Priyabrata Santra Mahesh Kumar R N Kumawat D K Painuli K M Hati G B M Heuvelink N H Batjes 《Journal of Earth System Science》2018,127(3):35
Characterization of soil water retention, e.g., water content at field capacity (FC) and permanent wilting point (PWP) over a landscape plays a key role in efficient utilization of available scarce water resources in dry land agriculture; however, direct measurement thereof for multiple locations in the field is not always feasible. Therefore, pedotransfer functions (PTFs) were developed to estimate soil water retention at FC and PWP for dryland soils of India. A soil database available for Arid Western India (N=370) was used to develop PTFs. The developed PTFs were tested in two independent datasets from arid regions of India (N=36) and an arid region of USA (N=1789). While testing these PTFs using independent data from India, root mean square error (RMSE) was found to be 2.65 and 1.08 for FC and PWP, respectively, whereas for most of the tested ‘established’ PTFs, the RMSE was >3.41 and >1.15, respectively. Performance of the developed PTFs from the independent dataset from USA was comparable with estimates derived from ‘established’ PTFs. For wide applicability of the developed PTFs, a user-friendly soil moisture calculator was developed. The PTFs developed in this study may be quite useful to farmers for scheduling irrigation water as per soil type. 相似文献
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This paper presents a method for the feasibility of an artificial recharge scheme in a limestone aquifer. A 3D digital groundwater flow model was developed and calibrated to gain a better understanding of the aquifer dynamics and to estimate its capacity for artificial recharge. Several scenarios, based on different pumping alternatives, were tested over a 30 year period. The results were then analysed by yearly input-output balances. Worst case scenario model output suggests that implementing the scheme might ensure a sustainable use of the aquifer in the future. 相似文献