紫色土水分特征曲线室内测定方法的对比

为探寻全吸力范围内土壤水分特征曲线的可靠测定方法,采用沙箱排水法、Hyprop仪蒸发法、压力膜仪排水法和露点水势仪蒸发法分吸力段测定盐亭紫色土耕地表层2~7 cm和亚表层7~12 cm土壤的水分特征曲线,对比测定结果的方法间差异,并分析其原因。结果表明:对于表层和亚表层土壤,低吸力段(h >-100 cm)水分特征曲线的沙箱法和Hyprop仪法的均方根误差E_RMS (θ)均较小,在0.026~0.082 cm3/cm3范围内,确定系数R2均大于0.962,说明这两种方法测定结果之间差异不大。高吸力段(h <-330 cm)的压力膜仪法与露点仪法测定结果之间的差异较大,E_RMS (θ)为0.062~0.097 cm3/cm3,R2较低,为0.775~0.952。因此,全吸力范围内水分特征曲线测定方法的选择与组合应考虑土壤孔径分布特征和研究目的。     

Application of passive source surface-wave method in site engineering seismic survey

Site engineering seismic survey provides basic data for seismic effect analysis. As an important parameter of soil, shear-wave velocity is usually obtained through wave velocity testing in borehole. In this paper, the passive source surface-wave method is introduced into the site engineering seismic survey and practically applied in an engineering site of Shijingshan District. By recording the ubiquitous weak vibration on the earth surface, extract the dispersion curve from the surface-wave components using the SPAC method and obtain the shear-wave velocity structure from inversion. Over the depth of 42 m underground, it totally consists of five layers with interface depth of 3.31, 4.50, 7.23, 17.41, and 42.00 m; and shear-wave velocity of 144.0, 198.3, 339.4, 744.2, and 903.7 m/s, respectively. The inversion result is used to evaluate site classification, determine the maximum shear modulus of soil, provide basis for further seismic hazard analysis and site assessment or site zoning, etc. The result shows that the passive source surface-wave method is feasible in the site engineering seismic survey and can replace boreholes, shorten survey period, and reduce engineering cost to some extent.     

煤层气直井产气曲线特征及其与储层条件匹配性

煤层气产气曲线类型与地质条件的匹配与否直接影响产气效果。以沁水盆地柿庄南区块排采4 a以上的直井为研究对象,在产气曲线类型划分基础上,分析不同产气曲线特征,进一步分析产气曲线与储层参数的匹配性。结果表明：研究区产气曲线可划分为单峰快速上升、单峰稳定上升、双峰后低和双峰后高4种类型。产气曲线所表现出的特征受控于储层原始渗透率,储层动力及压裂效果。单峰快速上升型适用于含气量大于12 m³/d、临储比大于0.4和渗透率大于0.1×10^-3 μm²的储层,该种曲线容易造成产气量的骤降;单峰稳定上升型适用的储层条件广泛,与储层参数匹配性较高;双峰后低型产气效果整体不佳,与储层参数的匹配性差;双峰后高型适用于压裂效果较好的井、对储层原始参数要求较低,其后峰产气量的增加速率影响整体的排采效果。基于上述分析,将储层划分为七种类型,对研究区及其相邻区块实施\     

方钢管混凝土框架在低周反复荷载作用下的非线性有限元分析

本文建立了方钢管混凝土框架结构的三维非线性有限元分析模型,用以研究方钢管混凝土框架在低周反复荷载作用下的抗震性能。该模型考虑了钢与混凝土的粘结滑移作用。通过与方钢管混凝土框架结构在低周反复荷载作用下试验所得的滞回曲线和刚度退化曲线的对比,发现该模型的计算结果较为精确,可以应用于方钢管混凝土框架的结构分析中。同时由试验和有限元分析计算的结果也可以得出结论,方钢管混凝土框架具有较好的抗震性能。     

频率测深波区视电阻率响应和正演计算

本文对频率测深电偶源发射时的波区视电阻率响应进行了较系统的讨论,指出了国内现有理论中的一些错误。研究发现,在进行波区视电阻率响应的理论推导时,当基底电阻率有限时进行零级近似是正确的,但当基底电阻率为无限大时,进行零级近似是不完善的,必须进行修改。利用正确的公式进行了视电阻率响应的正演计算,结果表明,利用零级近似得出的公式与利用一级近似得出的公式计算的视电阻率响应曲线首支部分符合较好,但对于有高阻基底存在的地电断面,响应曲线尾支差异很大。     

Flood‐based analysis of high‐magnitude sediment transport using a non‐parametric method

Upland erosion and the resulting reservoir siltation is a serious issue in the Isábena catchment (445 km² Central Spanish Pyrenees). During a three‐month period, water and sediment fluxes have been monitored at the catchment outlet (Capella), two adjacent subcatchments (Villacarli, 41 km²; Cabecera, 145 km²) and the elementary badland catchment Torrelaribera (8 ha). This paper presents the results of the monitoring, a method for the calculation of a sedigraph from intermittent measurements and the derived sediment yields at the monitored locations. The observed suspended sediment concentrations (SSCs) demonstrate the role of badlands as sediment sources: SSCs of up to 280 g l^?1 were encountered for Villacarli, which includes large badland areas. SSCs at the Cabecera catchment, with great areas of woodland, barely exceeded 30 g l^?1. SSCs directly at the sediment source (Torrelaribera) were comparable to those at Villacarli, suggesting a close connection within this subcatchment. At Capella, SSCs of up to 99 g l^?1 were observed. For all sites, SSC displayed only a loose correlation with discharge, inhibiting the application of a simple sediment rating curve. Instead, ancillary variables acting as driving forces or proxies for the processes (rainfall energy, cumulative discharge, rising/falling limb data) were included in a quantile regression forest model to explain the variability in SSC. The variables with most predictive power vary between the sites, suggesting the predominance of different processes. The subsequent flood‐based calculation of sediment yields attests high specific sediment yields for Torrelaribera and Villacarli (6277 and 1971 t km^?2) and medium to high yields for Cabecera and Capella (139 and 410 t km^?2) during the observation period. In all catchments, most of the sediment was exported during intense storms of late summer. Later flood events yield successively less sediment. Relating upland sediment production to yield at the outlet suggests considerable effects of sediment storage within the river channel. Copyright © 2008 John Wiley & Sons, Ltd.     

Bayesian analysis of stage–fall–discharge models for gauging stations affected by variable backwater

Parsimonious stage–fall–discharge rating curve models for gauging stations subject to backwater complications are developed from simple hydraulic theory. The rating curve models are compounded in order to allow for possible shifts in the hydraulics when variable backwater becomes effective. The models provide a prior scientific understanding through the relationship between the rating curve parameters and the hydraulic properties of the channel section under study. This characteristic enables prior distributions for the rating curve parameters to be easily elicited according to site‐specific information and the magnitude of well‐known hydraulic quantities. Posterior results from three Norwegian and one American twin‐gauge stations affected by variable backwater are obtained using Markov chain Monte Carlo simulation techniques. The case studies demonstrate that the proposed Bayesian rating curve assessment is appropriate for developing rating procedures for gauging stations that are subject to variable backwater. Copyright © 2009 John Wiley & Sons, Ltd.     

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印度洋dipole事件的年际变化与ENSO事件的联系

通过对nino3指数和DMI序列的分析，发现两种物理现象都有4a左右的主要周期，而且印度洋偶极子事件还存在有2a左右的振荡周期，而厄尔尼诺事件在2a时间尺度上周期性不明显；对nino3指数和DMI进行年际时间尺度滤波，结果表明，在年际时间尺度上，两者的相关性比未滤波时有了一定的提高；对年际滤波之后的偶极子事件和ELNINO事件的相关分析可以发现，ELNINO对于印度洋偶极子事件的影响要大于IOD对于太平洋ENSO事件，显示了两者物理现象的影响不对称。     

基于细化分层法探讨面波频散曲线反演参数的简化

常规频散曲线反演过程中需要不停地改变分层数、层厚度和层速度等参数,实现过程相对繁琐,而采用细化分层法对反演参数进行简化则避免了上述缺点。具体思路为:根据目的层探测深度(如20m)将地下介质分为若干个(20个)厚度为1m的薄层和1个均匀半空间层(共21层),这样在反演中分层数和层厚度均为已知参量,反演过程只需修改速度参数即可,避免了改变分层数和层厚度等参数,显著简化了反演计算过程。正演计算和反演结果均表明:细化分层与实际分层计算出的频散曲线是等效的,细化分层反演结果的总体效果与真实模型非常接近,这说明细化分层方法用于频散曲线反演是切实可行且有效的;将地下介质划分为1m厚的薄层,反演后每层均可得到1个横波速度,能满足反演分辨率的要求;由于实际地下介质的速度是随深度渐变的,细化分层后比按频散曲线拐点分层(每分层的厚度可能是几米或几十米,同一分层内介质的横波速度相等)更接近实际情况。