瓯江河口江堤控制线的研究

依据河口的河宽放宽率半理论公式,运用河势演变分析与用一维、二维数值模型的模拟等手段,从河道的防洪、河势、水流、航运等方面及其对环境影响的角度出发,对不同江堤控制线方案进行了比选与论证,提出了江堤控制线的推荐方案。     

加筋及灌浆联合处理软土地基在路基加宽中的应用和分析

提出了采用“土工合成材料加筋+路基注浆+桩支撑”系统的复合地基,并运用于软土地基上路基加宽。采用弹塑性有限元程序分析比较了路堤在加桩和不加桩情况下的沉降大小、不均匀沉降以及土体中的应力水平;特别是桩-土相互作用的计算分析与实测资料的分析比较。得出了一些相关结论,从而为工程实践提供了一定的理论依据。     

焦家断裂带南延问题及南延段找矿前景分析

焦家断裂带位于龙(口)-莱(州)断裂带的南段,为胶西北地区三大著名的金成矿带之一。焦家断裂带南段因第四系覆盖至寺庄以南去向不明。根据近几年的研究成果,认为焦家断裂带应为龙(口)-莱(州)断裂带南段的高家庄子-紫罗姬家段,特别是南部的徐村院-紫罗姬家段所揭露断裂带应为焦家断裂带在该区的南延并具有较好的找矿前景。     

新厝公路拓宽工程软土路基施工监测分析

福清新厝公路拓宽海堤段海堤内侧采用分级加载进行路基施工填筑软基加例处理,通过3个断面监测数据分析,最大水平位移日变量为2．28mm／d,最大沉降速率为5．97nm/d,各测点的沉降速率和水平位移均在安全控制范围之内。至监测末期最大总沉降量占淤泥层厚度7％,海堤地基固结度76．3％～85．0％,但尚有10．9～15．8m...     

非对称交通荷载作用下拓宽路堤动力特性分析

针对山西省境内长期承受非对称交通荷载的公路拓宽路堤,采用FLAC~(3D)建立数值模型,土工格栅采用FLAC~(3D)内置土工格栅单元(geogrid)模拟,其余部分均采用实体单元,屈服准则采用Mohr-Coulomb准则。将交通荷载简化为半正弦波荷载,分析非对称交通荷载作用下不加筋和加筋两种工况下拓宽路堤的变形特性及稳定性,进而改变拓宽路堤部分填土参数、交通荷载幅值、频率和行车间隔等参数,分析其对加筋工况下拓宽路堤变形的影响。结果表明:非对称交通荷载作用下,设置土工格栅加筋对新、旧路堤变形的约束作用有限,但能提高路堤的整体稳定性;增大拓宽路堤填土的压缩模量和黏聚力,可减小新、旧路堤沉降差;增大交通荷载一侧幅值会引起新、旧路堤过大差异沉降;增大交通荷载频率和时间间隔,路堤沉降均逐渐减小,但沉降差保持不变。上述结论对受非对称交通荷载拓宽路堤的施工提供了一定的理论依据。     

Riparian reforestation and channel change: A case study of two small tributaries to Sleepers River, northeastern Vermont, USA

Measurements of two small streams in northeastern Vermont, collected in 1966 and 2004–2005, document considerable change in channel width following a period of passive reforestation. Channel widths of several tributaries to Sleepers River in Danville, VT, USA, were previously measured in 1966 when the area had a diverse patchwork of forested and nonforested riparian vegetation. Nearly 40 years later, we remeasured bed widths and surveyed large woody debris (LWD) in two of these tributaries, along 500 m of upper Pope Brook and along nearly the entire length (3 km) of an unnamed tributary (W12). Following the longitudinal survey, we collected detailed channel and riparian information for nine reaches along the same two streams. Four reaches had reforested since 1966; two reaches remained nonforested. The other three reaches have been forested since at least the 1940s. Results show that reforested reaches were significantly wider than as measured in 1966, and they are more incised than all other forested and nonforested reaches. Visual observations, cross-sectional surveys, and LWD characteristics indicate that reforested reaches continue to change in response to riparian reforestation. The three reaches with the oldest forest were widest for a given drainage area, and the nonforested reaches were substantially narrower. Our observations culminated in a conceptual model that describes a multiphase process of incision, widening, and recovery following riparian reforestation of nonforested areas. Results from this case study may help inform stream restoration efforts by providing insight into potentially unanticipated changes in channel size associated with the replanting of forested riparian buffers adjacent to small streams.     

A full-scale field experiment to study the thermal-deformation process of widening highway embankments in permafrost regions

As one of the widely used upgrading way in road engineering, the widening embankment(WE) has suffered evident differential deformation, which is even severer for highway in permafrost regions due to the temperature sensitivity of frozen soil and the heat absorption effect of the asphalt pavement. Given this issue, a full-scale experimental highway of WE was performed along the Qinghai-Tibet Highway(QTH) to investigate the differential deformation features and its developing law. The continuous three years' monitoring data taken from the experimental site, including the ground temperature and the layered deformation of WE and original embankment(OE), were used to analyze the thermal-deformation process. The results indicate that the widening part presented the remarkable thermal disturbance to the existing embankment(EE). The underlying permafrost was in a noteworthy degradation state, embodying the apparent decrease of the permafrost table and the increase of the ground temperature. Correspondingly, the heat disruption induced by widening led to a much higher deformation at the widening side compared to the original embankment, showing a periodic stepwise curve. Specifically, the deformation mainly occurred in the junction of the EE and the widening part, most of which was caused by the thawing consolidation near the original permafrost table. In contrast, the deformation of EE mainly attributed to the compression of the active layer. Furthermore, it was the deformation origination differences that resulted in the differential deformation of WE developed gradually during the monitoring period, the maximum of which reached up to 64 mm.     

Computer program for stability analysis of steep,cohesive riverbanks

The ability to predict the stability of eroding riverbanks is a prerequisite for modelling alluvial channel width adjustment and a requirement for predicting bank erosion rates and sediment yield associated with bank erosion. Mass‐wasting of bank materials under gravity occurs through a variety of specific mechanisms, with a separate analysis required for each type of failure. This paper presents a computer program for the analysis of the stability of steep, cohesive riverbanks with respect to planar‐type failures. Planar‐type failures are common along stream channels destabilized by severe bed degradation. Existing stability analyses for planar‐type failures have a number of limitations that affect their physical basis and predictive ability. The computer program presented here is based on an analysis developed by Darby and Thorne. The software takes account of the geotechnical characteristics of the bank materials, the shape of the bank profile, and the relative elevations of the groundwater and surface water to estimate stability with respect to mass failure along a planar‐type failure surface. Results can be displayed either in terms of a factor of safety (ratio of resisting to driving forces), or probability of failure. The computer analysis is able to determine the relative amounts of bed degradation and bank‐toe erosion required to destabilize an initially stable bank. Data for the analysis are supplied in the form of either HEC‐2 hydrographic survey data files or user‐supplied bank profile data, in conjunction with user‐supplied geotechnical parameter values. Some examples, using data from the Upper Missouri River in Montana, are used to demonstrate potential applications of the software. Copyright © 2000 John Wiley & Sons, Ltd.     

Spatio‐temporal patterns of channel changes in response to a major flood event: the case of the Magra River (central–northern Italy)

On October 25^th 2011, the Magra River (central–northern Italy) was affected by a significant flood event with an estimated return interval ranging from 30 to 200 years. This study investigates the morphological responses of the Magra River to this major flood event with the aims of (i) documenting the channel changes which occurred in response to the flood; (ii) analysing this response within the context of the historical trend of width changes; (iii) investigating the possible factors controlling the spatial pattern and the intensity of the observed changes. Significant channel widening was documented along the entire length studied (about 34 km), ranging from 3% to 90% of the pre‐flood channel width. Braided reaches were characterized by the most severe planimetric changes. Although characterized by high rates of change, these variations are, however, amply included in the historical range of channel width variability over approximately the last 150 years (from 1877 to present day), and are comparable with ( though generally lower than) the channel width of the 1950s. Statistical analyses (simple and multiple regressions) between the observed changes in channel width and a series of selected morphological and hydraulic controlling factors showed no robust correlations to explain the spatial pattern and the variability of channel adjustments. Instead, major adjustments occurred along reaches characterized by the confluence of those streams draining the sub‐catchments where the storm was concentrated. Copyright © 2014 John Wiley & Sons, Ltd.     

Process-based modeling of the overflow-induced growth of erosional channels

A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a non-cohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally.