A new method for testing pile by sin- gle-impact energy and P-S curve     

许昭永  段永康  王彬  胡毅力  杨润海  许峻  赵晋明 《地震学报(英文版)》2004,17(Z1)

Introduction Through many year's practices by vast numbers of scientific and technological workers andefforts from all aspects, the dynamic testing method of high-low strain has formally entered intothe technical code of foundation pile test of construction at last (The Industry Standards of thePeople's Republic of China, 2003). The striking mode of the dynamic testing method of high strainis stipulated as hammer in the code, the striking of rocket can also be used. The latter is widely…  相似文献   

Bearing capacity of rock over mined cavities in Nottingham   总被引：1，自引：0，他引：1  

A.C Waltham  G.M Swift 《Engineering Geology》2004,75(1):15-31

A significant geohazard is created in Nottingham, UK, by hundreds of man-made caves cut in the weak sandstone beneath the city centre. Stability of the caves has been assessed by a single full-scale loading test, by numerical modelling with FLAC and by physical modelling in plaster. For typical caves 4 m wide, bearing capacity of the rock roof rises from 2 MPa where it is 1 m thick to 8 MPa where 3 m thick. Stability decreases over wider caves and where the loading pad edge is over the edge of the cave. Numerical modelling of a very wide cave revealed the failure mechanisms and also showed that an internal support wall increased roof bearing capacity by 50%. Local building regulations that require 3-5 m of rock cover over the sandstone caves appear to be conservative. In stronger rocks, including karstic limestone, a guideline that cover thickness exceeds 70% of the cave width appears to be appropriate.  相似文献   

Bearing capacity of unsaturated expansive soils     

Yongfu Xu 《Geotechnical and Geological Engineering》2004,22(4):611-625

It is difficult to determine the bearing capacity of a foundation in unsaturated expansive soil, although this is most important. The bearing capacity of unsaturated expansive soil is related to the drying and wetting environment. Swelling pressure occurs when the soil volume change is constrained as an expansive soil is inundated. The expansive lateral pressure, induced by the swelling pressure is similar to the passive earth pressure. By considering the effect of the expansive lateral pressure in Terzaghi's bearing capacity formula, the bearing capacity of unsaturated expansive soil is derived. Because it is very difficult to measure suction in situ, the bearing capacity is expressed using the expansive lateral pressure offers a feasible approach to calculate the bearing capacity of a foundation in unsaturated expansive soil, when suction is not measured. Plate load tests to measure the bearing capacity in situ were performed for the foundation in natural soil and saturated soil immersed by water. The verification of the bearing capacity formulae presented in this paper is conducted by comparing the predicted results with the results of the plate load tests on unsaturated expansive soils in Handan and Bingxia, China.  相似文献   

The structural role of Ti in aluminosilicate liquids in the glass transition range: insights from heat capacity and shear viscosity measurements     

Mathieu Roskosz  M.J Toplis 《Geochimica et cosmochimica acta》2004,68(3):591-606

The shear viscosities and 1 bar heat capacities of glasses and melts along the 67mol% silica isopleth in the system SiO₂-Al₂O₃-Na₂O-TiO₂ have been determined in the temperature ranges 780-1140 K and 305-1090 K respectively. Anomalous behaviour of both these properties is observed for compositions rich in TiO₂ and/or Al₂O₃, an observation attributed to liquid-liquid phase separation followed by anatase crystallization. For samples which do not show anomalous behaviour, it is found that the partial molar heat capacity of the TiO₂ component previously determined in Al-free compositions reproduces our heat capacities to within 1.3%. Viscosity data show that addition of TiO₂ tends to increase viscosity and melt fragility at constant temperature. Furthermore, heat capacity and viscosity data may be combined within the framework of the Adam-Gibbs theory to extract values of the configurational entropy of the liquids and qualitative estimates of the variation of the average energy barrier to viscous flow. Configurational entropy at 900K is inferred to decrease upon addition of TiO₂, in contrast to previous results from Al-free systems. The compositional limit separating normal from anomalous behaviour, as well as the data for homogenous melts have been used to constrain the structural role of Ti in these samples. Our data are consistent with a majority of Ti in five-fold coordination associated with a titanyl bond, in agreement with previous spectroscopic studies. Furthermore, we find no evidence for a Ti-Al interaction in our samples, and we are led to the conclusion that Al and Ti are incompletely mixed, a hypothesis consistent with the observed reduction of configurational entropy upon addition of TiO₂, suggesting an important role of medium range order in controlling the variations in thermodynamic properties.  相似文献   

Dynamic theory of rigid-plasticity     

Meiketsu  Binh Xuan  Noboru  Katsuhisa 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):635-647

This paper deals with an analysis method for the response and motion of soil-like rigid-plastic bodies under seismic loading conditions. A continuity condition to determine the acceleration distribution within the rigid-plastic body when the failure occurs during seismic motions is proposed. Combining this continuity condition of acceleration and the ‘Generalized Limit Equilibrium Method (GLEM)’, the responses of the earth structure during seismic motions as well as the permanent displacements can be obtained, where GLEM is one of the limit equilibrium methods proposed by the authors for static problems and providing the approximate solution for Kötter's equation. The theoretical formulation of the method, the illustrative examples, and some comparisons between the analytical and experimental results are demonstrated.  相似文献   

Delayed geochemical hazard: Concept, digital model and case study     

CHEN Ming  FENG Liu  Jacques Yvon 《中国科学D辑(英文版)》2005,48(Z2)

Delayed Geochemical Hazard (DGH briefly) presents the whole process of a kind of serious ecological and environmental hazard caused by sudden reactivation and sharp release of long-term accumulated pollutant from stable species to active ones in soil or sediment system due to the change of physical-chemical conditions (such as temperature, pH, Eh, moisture, the concentrations of organic matters, etc.) or the decrease of environment capacity. The characteristics of DGH are discussed. The process of a typical DGH can be expressed as a nonlinear polynomial. The points where the derivative functions of the first and second orders of the polynomial reach zero, minimum and maximum are keys for risk assessment and harzard pridication.The process and mechanism of the hazard is due to the transform of pollutant among different species principally. The concepts of "total releasable content of pollutant", TRCP, and "total concentration of active specie", TCAS, are necessarily defined to describe the mechanism of DGH. The possibility of the temporal and spatial propagation is discussed. Case study shows that there exists a transform mechanism of "gradual release" and "chain reaction" among the species of the exchangeable and the bounds to carbonate, iron and manganese oxides and organic matter, thus causing the delayed geochemical hazard.  相似文献   

Developing efficient scalar and vector intensity measures for IDA capacity estimation by incorporating elastic spectral shape information     

Dimitrios Vamvatsikos  C. Allin Cornell 《地震工程与结构动力学》2005,34(13):1573-1600

Scalar and vector intensity measures are developed for the efficient estimation of limit‐state capacities through incremental dynamic analysis (IDA) by exploiting the elastic spectral shape of individual records. IDA is a powerful analysis method that involves subjecting a structural model to several ground motion records, each scaled to multiple levels of intensity (measured by the intensity measure or IM), thus producing curves of structural response parameterized by the IM on top of which limit‐states can be defined and corresponding capacities can be calculated. When traditional IMs are used, such as the peak ground acceleration or the first‐mode spectral acceleration, the IM‐values of the capacities can display large record‐to‐record variability, forcing the use of many records to achieve reliable results. By using single optimal spectral values as well as vectors and scalar combinations of them on three multistorey buildings significant dispersion reductions are realized. Furthermore, IDA is extended to vector IMs, resulting in intricate fractile IDA surfaces. The results reveal the most influential spectral regions/periods for each limit‐state and building, illustrating the evolution of such periods as the seismic intensity and the structural response increase towards global collapse. The ordinates of the elastic spectrum and the spectral shape of each individual record are found to significantly influence the seismic performance and they are shown to provide promising candidates for highly efficient IMs. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

挤扩支盘桩极限承载力的预测   总被引：2，自引：0，他引：2  

高笑娟  杨晓斌 《岩土工程技术》2005,19(5):254-257

用双曲线方法对110根挤扩支盘桩的极限承载力进行预测,并与直杆桩预测结果进行对比。结果表明由于支盘桩受力性状复杂,加载前期和中期预测精度较高,后期较低,误差超过15%;支盘桩的沉降曲线出现台阶时预测值与实测值误差较大;支盘桩极限承载力的预测精度与工程地质条件和桩本身的参数密切相关,桩身参数和地质条件相同条件下各桩预测精度比较接近。总体上直杆桩的预测结果优于支盘桩。  相似文献   

钻孔灌注桩后压浆作用机理与应用     

陈飞  兰凯 《地质科技情报》2005,24(Z1):97-100

通过对桩侧和桩底后压浆,可大幅度提高钻孔灌注桩单桩承载力.应用桩-土理论分析了后压浆中浆液对土体及桩体的作用,并从分析影响桩基承载力的因素出发,研究了后压浆的作用机理.在渗透率小的地层中后压浆以压密注浆为主,在渗透率大的地层中后压浆以渗透注浆为主.为避免过分压裂土层,在压浆过程中应控制灌浆压力.压浆量是影响后压浆质量和提高单桩承载力的关键因素之一.  相似文献   

Analysis on Bearing Capacity of Tunnel-Type Anchorage of a Long-Span Suspension Bridge     

Zhu Yu Wei Jun Yang Manjuan Li Hao Liu Hongqing 《中国地质大学学报(英文版)》2005,16(3):277-282

INTRODUCTION Tunnel typeanchoragehasobviousadvantages inbearingcapacityversusinvestment(LiuandHu,1996).However,itisrarelyusedinapracticalpro jectbecauseofitsrequirementofgoodrockcondi tions.Siduhebridge(Fig.1),whichliesintheBa dongmountainsinthewestplatea…  相似文献