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1.
Most of the existing relevant materials have been obtained from experiments, in which evaluating the added mass at the resonant frequency corresponding to the peak of a frequency-response curve obtained from the “forced” vibration analysis is the most popular technique. In this paper, a simple experimental method was presented where the “free” vibration responses instead of the “forced” ones were used to determine the values of mah and Iap. The main part of the experimental system is composed of a floating body (model) and a spring–shaft shaker. The “free” vibration of this main part was induced by imposing on it an initial displacement (and/or an initial velocity), and from the time histories of displacements information such as the “damped” natural frequencies, damping ratios, sectional added mass coefficients (CV and CP) were obtained. Since the displacements of the spring–shaft shaker are “translational” and those of the floating body due to pitch motions are “angular”, a technique for the transformation between the associated parameters of the two components of the main part was presented. 相似文献
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介绍了煤矿井筒检查孔的特点和技术、质量要求,总结了以往工程中的经验教训,针对工程中的技术难点,如取心、孔斜控制、抽水作业和冲洗液选择与维护等影响质量、工期的关键环节提出了技术措施,为优质、高效施工此类工程提供借鉴. 相似文献
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分析了深厚表土层地面注浆加固过程中井壁的受力特点,介绍了金桥矿副井表土段地面注浆加固过程中井壁的应变观测结论,提出了深厚表土层井壁外注浆加固工程的井壁安全保证核心技术。 相似文献
6.
Karst Hazard Assessment of Eastern Saudi Arabia 总被引:1,自引:0,他引:1
Karst phenomena exist in areas in the eastern part of Saudi Arabia, forming solution features such as sinkholes, collapsed dolines and solution caverns, as a result of the chemical leaching of the carbonate and evaporite formations by percolating water. The instability of these karst phenomena could produce land subsidence problems. This paper reviews the geology of documented karstic rock units in Saudi Arabia and proposes a simple engineering classification of the solution features characteristic of limestone. Two case histories in the Dhahran area, eastern Saudi Arabia, will be used as examples for the application of a modified engineering classification. 相似文献
7.
The validity of the Winkler foundation model is investigated by predicting the experimentally measured displacement transfer functions and strain spectra of a single pile embedded in a sandbox and supporting a single-degree-of-freedom superstructure. The foundation-superstructure system is a scale model and was subjected to shake table excitations. The distributed springs and dashpots of the Winkler foundation model are frequency dependent and the calibrated model predicts satisfactorily the displacement transfer function at different depths for both fixed- and free-tip pile conditions. On the other hand, the pile-axial-strains are substantially underestimated when expressed in terms of the second derivative of the computed elastic line of the pile. It is shown that a much more dependable prediction is achieved when pile-axial-strains are expressed in terms of the inertial forces acting along the pile-superstructure system. 相似文献
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Several theoretical, empirical and semi-empirical methods are available in the literature to predict settlement of drilled
shafts in sandy soils. In the Arabian Gulf countries, specifically in the United Arab Emirates, equations and procedure from
the rest of the world are being used in analysis and design of drilled shafts without proper validation. It is the aim of
this study to assess the applicability and evaluate the accuracy of two well known, and commonly used methods for pile prediction
in the United Arab Emirates (UAE), namely Vesic (1977) and Poulos (1979), via comparison with data from field pile load tests
conducted on shafts drilled in the region. Some of these tests were conducted for the purpose of this study, while others
were made available through the courtesy of International Piling Contractors who are active in the region (e.g. Bauer International
and Swiss Borings). Pile load test data were analyzed to back-calculate the model parameters related to settlement under different
loading stages. Geological data and soil properties were obtained from studies conducted at the relevant sites. An effort
is made to correlate soil properties with the prediction models. Statistical analysis is conducted to assess the accuracy
of the results obtained from the two methods at different stages of loading via those obtained from pile load tests. Moreover,
a detailed parametric study is conducted to assess the effect of the related parameters on the predicted pile settlement and
the estimated settlement at different stages of loading. The study concluded with a recommendation of the most appropriate
models and procedures to be followed for predicting the settlement of drilled shafts in the UAE, together with useful charts
and correlation relations. Results showed that settlement values predicted by Vesic (1977) and Poulos (1979) overestimates
the true values.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Rodrigo Salgado 《国际地质力学数值与分析法杂志》2011,35(15):1605-1635
In recent years, pile jacking has become a viable alternative installation method for displacement piles. Pile jacking produces minimal noise, vibration and air pollution during installation. In addition, it is possible, at the end of jacking, to have a good estimate of the ultimate static capacity of the pile. In this paper, the shaft resistance of piles jacked into sand is studied using one‐dimensional finite element analysis. The finite element simulations, using a two‐surface plasticity model, demonstrate the effects of relative density and confinement on the unit shaft resistance of piles jacked in sand. The impact of the number of jacking strokes on the unit shaft capacity is also assessed. Based on the numerical results, we developed equations for shaft resistance quantifying the effects of relative density, initial confinement and number of jacking strokes. Predictions using these equations are compared with data obtained from centrifuge tests and field tests. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献