P波、SH波、面波数据分析方法的对比与剪切模量的确定

地震折射法普遍用来圈定岩石和地层的几何形态。此外,也可用于提取与速度相关的信息,比如:土壤和岩石的力学性质,然而这需要一个地表下速度变化的可靠模型。对折射P 波和SH波的首波以及表面波数据进行分析有3种不同的技术: 追逐时距曲线的延迟时间法, 层析成像法和面波多波分析(MASW)法。从前两种方法的比较结果看,对于高分辨率分层使用传统的追逐时距曲线的延迟时间法是最好的,层析成像法(P波测量)不能发现地下水位面,但是可测量到地下水位面附近速度的逐渐变化;另一方面, 对于介质速度的逐渐增加,传统的SH波的探测无用,但层析成像法却较适合。 此外, 层析成像法或 MASW法适宜用来建立细微的空间速度变化模型,与折射SH波层析成像法相比,MASW法显示略低的速度,而显示的速度梯度也是反向的。 这项研究同样适用于原位剪切模量的比较, 等等。也就是用剪切波速度进行计算, 并采用经验关系确定剪切模量,对于砂的剪切模量,相对于原位测量,经验关系值要更大一些。     

花岗岩不同土地利用类型坡地水土流失特征*

利用福建省安溪水土保持试验站的实测资料,对花岗岩不同土地利用类型坡地的水土流失特征进行了初步研究,试验结果说明,坡地只要有一定的植被覆盖和适当的坡地工程,水土流失均可得到控制.松耕使坡耕地土壤侵蚀力急剧下降,必须加强夏季园面覆盖.建议利用USLE进行土壤侵蚀预测时,未扰动自然课露坡地C取值0.1-0.3.实测结果显示,香根草带和牧草覆盖均有良好的保持水土效益,与山边沟工程结合,可以在较陡坡地果园开发中替代梯田台地进行推广.     

Retrieval of Substrate Bearing Strength from Hyperspectral Imagery during the Virginia Coast Reserve (VCR’07) Multi-Sensor Campaign

Hyperspectral imagery (HSI) derived from remote sensing can delineate surface properties of substrates such as type, moisture, and grain size. These are critical parameters that determine the substrate bearing strength. Although HSI only sees the surface layer, statistics can be derived that relate surface properties to the likely bearing strength of soils in particular regions. This information can be used to provide an initial map estimate on large scales of potential bearing strength. We describe an initial validation study at the Virginia Coast Reserve relating airborne HSI to in situ spectral and geotechnical measurements through a spectral-geotechnical lookup table (LUT).     

砂土与EPS颗粒混合的轻质土的动剪切模量衰减特性分析

动荷载下砂土与EPS颗粒混合的轻质土（LSES）的割线剪切模量Gsec随着剪应变的累积会发生衰减，基于不同水泥掺量和EPS含量的LSES试样的动三轴试验结果，建立了与围压、剪应变、水泥掺量等因素相关的Gsec的经验衰减模型。通过比较发现，LSES与砂及胶结砂的Gsec衰减模型具有一定相似性，即Gsec与yd呈双曲线关系，与σc为指数关系。此外，由于水泥胶结的约束作用，Gsec对σc的依存度随水泥掺量的增加而减小，这种依存程度通过参数n反映出来，但当水泥掺量达到10％时n随其的变化就不明显了，这是因为胶结强度已经增大到使得LSES中颗粒间的相对位置不易发生错动的程度。     

Anisotropic compression of edingtonite and thomsonite to 6 GPa at room temperature

Polycrystalline samples of natural edingtonite (New Brunswick, Canada) and thomsonite (Oregon, USA) were studied up to 6 GPa using monochromatic synchrotron X-ray powder diffraction and a diamond-anvil cell with a methanol:ethanol:water mixture as a penetrating pressure-transmitting fluid. Unlike natrolite, previously studied under the same conditions, edingtonite and thomsonite do not show any apparent pressure-induced hydration (PIH) or phase transitions. All these fibrous zeolites are characterized by their anisotropic compressibilities, with the linear compressibilities of the fibrous chains (c-axis) being as small as one third of those perpendicular to the chains (a-, b-axes); for edingtonite, ₀ ^a =0.0050(3) GPa^–1, ₀ ^b =0.0054(2) GPa^–1, ₀ ^c =0.0034(1) GPa^–1; for thomsonite, ₀ ^a = 0.0080(2) GPa^–1, ₀ ^b =0.0084(2) GPa^–1, ₀ ^c =0.0032(1) GPa^–1. The pressure–volume data were fitted to a second-order Birch–Murnaghan equation of state using a fixed pressure derivative of 4. As a result of the 0000-type connectivity of the chains, the bulk modulus of edingtonite is found to be about 40% larger than that of thomsonite; K^EDI ₀=73(3) GPa, K^THO ₀=52(1) GPa. Distance least-squares refinements were used to model the expected framework, following the observed linear compression behaviors. The chain-bridging T–O–T angle is proposed to be correlated with the different compressibilities across the chains in each framework type.     

Determination of unconfined compressive strength and Young's modulus of porous materials by indentation tests

The formation of a compacted zone under the indenter seems to be the major factor controlling the indentation process in porous rocks. In the case of very porous materials, where the pore structure fails and deformation (by structural collapse) proceeds with almost no increase in the applied load and with very limited damage to the surrounding material, no chipping is observed. The extent of the compacted zone is controlled by the porosity of the material and by the strength of its porous structure. This paper presents an interpretation model developed by the authors to obtain the uniaxial compressive strength of porous materials from the results of indentation tests. It is based on the model proposed by Wilson et al. (Int. J. Mech. Sci., 17, 1975, 457) for the interpretation of indentation tests on compressible foams and on an estimation by the authors of the extent of the compacted zone under the indenter. The results of indentation tests can also be used to obtain the Young's modulus of the material with a model proposed by Gill et al. (Proceedings of the 13th Canadian Symposium on Rock Mechanics, 1980, 1103). Uniaxial compression and indentation tests have been performed on artificial porous materials showing porosities varying between 44 and 68%. The uniaxial compressive strength values obtained from both types of test show a very good agreement. For the Young's modulus, the values obtained from the two types of test are different but the variation of the moduli with porosity is the same. Finally, a parameter called permanent penetration modulus is proposed as a means of characterizing the uniaxial compressive strength of porous materials.     

Effective elastic properties of the double‐periodically cracked plates

In this paper, the interaction of double‐periodical cracks is accurately solved based on the isolating analysis procedure, superposition principle, pseudo‐traction method, Chebyshev polynomial expansion and crack‐surface collocation technique. The jump displacement crossing crack faces, the average additional strain and therefore the effective compliance of the double‐periodically cracked plate are directly determined. The numerical results for axial‐symmetrically distributed double‐periodical cracks, general double‐periodical cracks with one collinear direction as well as two sets of double‐periodical cracks with same size and square distribution are given in this paper. And the partial typical numerical results are compared with the previous works. The analysis shows that the anisotropy induced by the general double‐periodical cracks is generally not orthogonal anisotropy. Only when the double‐periodical cracks are axial‐symmetrically distributed, is the anisotropy orthogonal. In this special cases, the effective engineering constants (consist of effective elastic modulus, the effective Poisson's ratio, the effective shear modulus) of cracked plate versus crack spacing, in the plane stress and plane strain conditions, respectively, are analysed. Copyright © 2005 John Wiley & Sons, Ltd.     

多功能孔压静力触探(CPTU)测试技术在软土工程性 质评价中的应用

本文首先对现代多功能CPTU测试技术作了简要的介绍,阐述了孔压静力触探的发展状况、仪器设备和操作要点;然后在归纳国内外相关文献与研究工作的基础上,重点探讨了利用多功能CPTU测试资料评价软土工程特性的方法,包括应力历史、强度特性、变形特性以及固结渗透特性等;文章还对国内多功能CPTU测试技术未来发展的趋势、途径进行了探讨,提出了一些建议。     

塔克拉玛干沙漠腹地风沙土的物理力学性质

风沙是形成于干旱、半干旱区的一种特殊性质的土,其力学性质不同于一般土体,结构松散性为其最主要的特点.本文通过对塔克拉玛干沙漠腹地风沙土样进行的试验,获得了风沙土基本力学参数:压缩模量为50.0～142.86MPa,是一种低压缩性土;为31°55′～36°19′;风沙土存在结构力,其力学效应相当于粘聚力,数值在0.6～9.3MPa之间.     

横波测井的原理和方法研究

充液井孔中的偶极子声源能在周围岩层和土层中激发弯曲模式声波,它们在截止频率附近,沿井轴传播的速度为井壁介质的横波速度．使用可调声功率源使偶极子声波测井系统能适应软、硬地层的现场井孔测试．相关法算出横波声速,野外测试的结果和理论计算值相符．计算动弹模量和剪切模量,确定破碎层位置,可用于工程地质勘察中