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141.
北京市区杂填土地基处理技术综述 总被引:2,自引:0,他引:2
北京市区存在许多杂填土回填地基,主要是人为挖沙等原因形成。该部分地基回填成分复杂,既有建筑垃圾、工业垃圾和生活垃圾,又有几者的混合,而且此种地基成层薄厚不一、具有湿陷性和负摩阻力、均匀性差、承载力低、压缩性高、不确定性成分大且无规律性,所以此种地基必须根据实际情况综合确定经济、适合和可靠的优化处理方案,进行地基处理后才能作为建(构)筑物地基。结合西南四环珠江绿苑工程,论述北京市区杂填土地基处理组合型(综合)技术,并通过试验结果和沉降观测资料分析多种地基处理技术相互结合在高层建筑中应用的效果,并得出结论。 相似文献
142.
In situ neutron diffraction study of deuterated portlandite Ca(OD)2 at high pressure and temperature
Hongwu Xu Yusheng Zhao Jianzhong Zhang Donald D. Hickmott Luke L. Daemen 《Physics and Chemistry of Minerals》2007,34(4):223-232
The structure of deuterated portlandite, Ca(OD)2, has been investigated using time-of-flight neutron diffraction at pressures up to ∼4.5 GPa and temperatures up to ∼823 K.
Rietveld analysis of the data reveals that with increasing pressure, unit-cell parameter c decreases at a rate about 4.5 times larger than that for a, which is largely due to rapid contraction of the interlayer spacing in this pressure range. Fitting of the determined cell
volumes to the third-order Birch–Murnaghan equation of state yields a bulk modulus (K
0) of 32.2 ± 1.0 GPa and its first derivative (K
0′) of 4.4 ± 0.6. Moreover, on compression, hydrogen-mediated interatomic interactions within the interlayer become strengthened,
as reflected by decreases in interlayer D···O and D···D distances with increasing pressure. Correspondingly, D–D, the distance
between the three equivalent sites over which D is disordered, increases, suggesting a pressure-induced hydrogen disorder.
This behavior is similar to that reported in brucite at elevated pressure. On heating at ∼2.1 GPa, cell parameter c increases more rapidly than a, as expected. However, because of the pressure effect, the thermal expansion coefficients, particularly along c, are much smaller than those at ambient pressure. With increasing temperature, the three partially occupied D sites become
further apart, and the D-mediated interactions, mainly the interlayer D···D repulsion, become weakened. 相似文献
143.
Classification of Vertical Wind Speed Profiles Observed Above a Sloping Forest at Nighttime Using the Bulk Richardson Number 总被引:5,自引:0,他引:5
Hikaru?KomatsuEmail author Norifumi?Hotta Koichiro?Kuraji Masakazu?Suzuki Taikan?Oki 《Boundary-Layer Meteorology》2005,115(2):205-221
Wind speed profiles above a forest canopy relate to scalar exchange between the forest canopy and the atmosphere. Many studies have reported that vertical wind speed profiles above a relatively flat forest can be classified by a stability index developed assuming wind flow above a flat plane. However, can such a stability index be used to classify vertical wind speed profiles observed above a sloping forest at nighttime, where drainage flow often occurs? This paper examines the use of the bulk Richardson number to classify wind speed profiles observed above a sloping forest at nighttime. Wind speed profiles above a sloping forest were classified by the bulk Richardson number Ri B . Use of Ri B distinguished between drainage flow, shear flow, and transitional flow from drainage flow to shear flow. These results suggest that Ri B is useful to interpret nighttime CO2 and energy fluxes above a sloping forest. Through clear observational evidence, we also show that the reference height should be high enough to avoid drainage-flow effects when calculating Ri B . 相似文献
144.
K. Blümel 《Boundary-Layer Meteorology》2000,97(2):251-271
An approximate method for calculating the relationship between z/L(z = reference height, L = Obukhov length) and the bulk Richardsonnumber is presented. If this relationship is known, the momentum andheat fluxes can be computed easily without any iteration. The avoidance of iteration can speed up computationsin large-scale models considerably (up to 10 times) and cases which do not converge or converge very slowly cannot occur. The proposed formulae take into account the difference between momentum (z0M) and heat roughnesslengths (z0H). Because the roughness lengths are not neglected at any step of the derivation, the resulting analytical formulae can be used not only between the surface and the reference height but also between two finite levels z1 andz2 (by replacing z0M and z0H by z1 and z by z2). Theequations remain correct even in the limit z1 z2.The formulae are based upon the (partially modified) Businger–Dyer flux–profile relationships and,consequently, they are restricted to predominantly homogeneous terrain.These new approximations are an improvement over the existing solutions because they are simpler than most of the formulae in the literature and are able to match the numerical exact solution for different parameter sets (Businger, Dyer, Högström) with an maximum error of about 2% for a wide range of z/L, z/z0M and z0M/z0H.Furthermore, in stable conditions, schemes with and without a finitecritical bulk Richardson number can be approximated. The possibleambiguity of the exact solution =f(RIB) in (moderately) stable conditions is discussed briefly. The performance of the new formulae is compared to the exact numerical solution and to different formulae proposed in the literature. 相似文献
145.
Simple analytic approximate solutions arepresented for the set of equations that follows fromthe Monin–Obukhov flux-profile relationships using thestability functions of Dyer (unstable case) andBeljaars–Holtslag (stable case). Several publicationsare devoted to the same subject, however the currentapproach contains some new features, namely: (a) itappears to be more accurate for unstable situationsand (b) it applies also to the general case where windspeed (u) and potential temperature() are given at different levels. In order toillustrate the accuracy of the approach a comparisonwith the actual solutions is presented for someselected combinations of and u levelstypical for various practical applications. 相似文献
146.
从历史时期森林变迁,林业与气候、经济林果适宜种植区、草场与气候、卫星遥感技术应用和森林防火服务方面综合了甘肃省关于林草科学研究和业务的进展,可供西北大开发参考。 相似文献
147.
《Engineering Geology》2000,56(3-4):293-303
This study aims at investigating the utilization of bottom ash obtained from four different power stations as a construction fill and landfill bottom liner. For the matrix material, commercial powdered bentonite, construction lime and natural clay were used. Compaction tests (Standard Proctor and vibratory hammer) were carried out on the different ratios of bottom ash and matrix material. The optimum water content ranged from 40 to 45% yielding a dry density mostly ca 1 Mg m−3. Uniaxial compressive strength of mixtures ranges from 0.1 to 0.5 kgf cm−2 which showed a 3–20-fold increase when tested on 28-day cured specimens. Triaxial compression tests yield varying rates of shear strength which also showed as high as an 11-fold increase for cured specimens. The hydraulic conductivity of those mixtures was mostly ca 10−4 cm s−1, which is not considered to be low enough for landfill lining. Leaching tests using deionized water were also performed to investigate the possible effect of leachate produced from the mixtures on the environment. In conclusion a light density and environmentally friendly mixture is determined and proposed as construction filler. 相似文献
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