寒区堤防砂土岸坡生态护坡技术研究

东北地区堤防多是砂堤,砂土质地松散、贫瘠。在降雨侵蚀和风力侵蚀联合作用下,砂堤坡面水土流失严重,降低了砂堤防洪质量,危及大堤安全。为了减少坡面降雨侵蚀和水土流失,保证砂堤的防洪质量,采用保水剂改良砂堤表层土壤为植被生长提供水分和养分,并通过单纯植被护坡方案和两种改良后生态护坡方案的室内外试验的对比,选取合适的护坡方案。结果表明:三维土工网垫和遮阳网在草籽发芽前期,能够较好地保护坡面和草籽,减少降雨侵蚀;在植被生长期,植株可以穿过三维土工网垫孔隙正常生长,植被根系发挥了铆钉作用,将三维土工网垫紧紧地锚定在坡面;三维土工网垫连同植被根系组成联合保护层,提升了整体加筋效果,但是由于遮阳网的孔隙过于细密,植被难以穿过遮阳网正常生长,将遮阳网顶起,无法像三维土工网垫那样与植被形成联合防护体系,整体加筋效果较差。     

植物根系固土护坡力学机理研究现状与进展

在对国内外主要相关研究成果进行系统介绍的基础上,详细论述了根系固坡机理的力学模型、根系和土壤-根系复合体的力学性能、边坡稳定的有限元数值模拟以及根系的分布特征,并探讨了植被护坡研究的发展趋势。     

原木植生挡墙技术在广东省中小河流岸坡生态防护中的应用——以重阳水治理工程为例

以广东省中小河流重阳水治理工程为例,阐述了原木植生挡墙生态护岸技术要点,并且通过对植物株高和基径生长的原型观测,株高和基径在3个月、6个月和12个月后平均值分别为12.8 cm、57.1 cm、147.9 cm以及0.34 cm、0.72 cm、1.25 cm,第1年株高和基径平均增长率分别为12.33 cm/m和0.10 cm/m。监测结果表明:施工3个月后可基本对岸坡复绿,植物根部对表层土壤已发挥锚固作用,基本恢复河岸带自然风貌和生态景观,可为我省中小河流岸坡生态治理提供技术参考。     

地肤根系的力学性质及对道路侵蚀的影响

基于黄土高原植物路防蚀对适宜植物的需要,对多年生草本植物地肤根系的抗剪切强度进行了测试,并在野外生长有地肤坡面的径流小区进行了冲刷试验。结果表明：相同试验条件下含有单株地肤根系的土样比不含地肤根系的土样,在100、200、300、400 kPa共4种不同垂直荷载压力下,其抗剪切强度分别提高了9.51%、14.42%、17.03%、7.35%;坡面冲刷单宽流量为1.67×10-4m3/(s·m)且坡面地肤覆盖度为0、20%、40%、60%、80%时,裸坡的侵蚀量分别是地肤坡面的2、7、12倍及29倍左右,这说明地肤对于提高土壤抗侵蚀性能有显著效果,是一种适宜栽培于黄土高原道路的植被品种。     

不同耕作措施及玉米生育期对黄壤坡耕地土壤团聚体稳定性的影响

为探讨耕作措施和玉米季对黄壤坡耕地土壤团聚体稳定性的影响,以横坡垄作坡面为研究对象,顺坡垄作坡面为对照,研究野外自然降雨条件下玉米季黄壤坡耕地土壤团聚体组成及其稳定性的变化特征,以期为山地黄壤区土壤抗蚀性研究提供理论依据。结果表明:①不同耕作措施对玉米种植土壤团聚体组成和稳定性影响显著,横坡垄作坡面较顺坡垄作含有更多大粒级团聚体;以(10,0.25]mm水稳性团聚体(WSA_>0.25)、平均质量直径(MWD)、几何平均直径(GMD)、结构体破坏率(PAD)、水稳性团聚体分形维数(D)、团聚体稳定性系数(ASI)为指标进行分析,得出横坡垄作坡面土壤团聚体稳定性较顺坡垄作坡面好。②随玉米生育期的推进,土壤大粒级团聚体含量及团聚体稳定性均呈现出显著升高的趋势,且在成熟期达极大值,表明玉米生育期也显著影响土壤团聚体组成及稳定性。③相关性分析得出,团聚体稳定性与根系密度、根表面积、根体积呈极显著正相关关系,根系的发育对增强研究区土壤团聚体稳定性具有重要的贡献。适宜的耕作措施和合理的种植模式均有助于研究区水土流失的有效防控。     

现浇网格生态护坡技术研究——以延庆试验区为例

为了研究现浇网格生态护坡技术在边坡治理中的适应性和效果,系统地介绍了该技术体系,并以北京延庆试验区为例,对网格内植物的生长情况和土壤的理化性质进行了调查分析。结果表明:完工4 a后,试验小区金叶莸的成活率达到94.3%,金叶莸新生枝叶繁茂,每株枝条平均生物量可达到29.3 g,平均株高为33.07 cm,平均覆盖度为533 cm2;与空白对照小区比较,网格内土壤中机质增加了28.11 g/kg,全氮增加了0.72 g/kg,速效磷增加了11.25mg/kg,速效钾增加了33.74 mg/kg,pH下降了0.71。在经济成本方面,该技术的后期养护时间为1～2 a,时间短,投入少,节约成本。试验区适用研究成果表明现浇网格生态护坡技术的水土保持、植被恢复效果良好,易于在各类边坡生态防护中推广应用。     

郑西客运专线黄土路堑高边坡植被防护技术

以郑西客运专线DK297+183至DK298+420的黄土路堑高边坡为试验段,探讨了采用工程防护与植被防护相结合的方法对黄土路堑高边坡进行防护的可行性,从边坡稳定和坡面植被根系特性两个方面分析了黄土路堑高边坡的适宜坡型,在此基础上进行了植被防护试验。试验结果表明,采用合理坡型,在坡面形成适宜植物生长的土壤环境,并进行植物的合理配置,该植被防护技术可应用于黄土路堑高边坡的防护且有利于植被恢复。     

基于SWAP模型的河套灌区向日葵农田土壤水盐通量模拟

为了探究河套灌区节水实施现状条件下农田土壤水盐动态变化规律,利用向日葵田间试验观测资料,对SWAP模型进行参数率定和验证,并利用该模型模拟向日葵生长条件下0～100 cm土层土壤水盐通量及水盐平衡状况。研究结果表明：在灌溉阶段,向日葵根系层土壤水分主要向下渗漏,水分通量和盐分通量为负,土壤盐分被淋洗;在非灌溉阶段,地下水向上补给向日葵根系层土壤,水分通量和盐分通量为正,根系层土壤积盐。2019、2020年模拟期间水分通量累计量分别为52.5、60.6 mm,盐分通量累计量分别为-4.5、-4.9 mg/cm²,0～100 cm土层土壤盐分通量分别增加了7.5、7.1 mg/cm²。向日葵现状灌溉条件下0～100 cm土层土壤积盐,可能产生土壤次生盐碱化的风险,向日葵生育期结束后需要进行秋浇淋洗盐分来保证下一年度向日葵的正常生长。     

紫花苜蓿根系拉拔试验研究

为了研究紫花苜蓿根系的拉拔力学性质和评价其根系固土力学机制的增强效应,采用室外原位拉拔试验分析了影响苜蓿根系拉拔力的因素。试验结果表明：① 紫花苜蓿根系拉拔力随着直径、根长、根系表面积的增大而增大,抗拉力与直径增长趋势呈指数关系,根长L2（20~30 cm）比根长L1（10~20 cm）平均拉拔力增大了69.62%,根长L3（30~40 cm）比根长L2平均拉拔力增大了61.7%,根长L3平均拉拔力比根长L1增大156.16%。② 拉拔力随根系表面积的增大而增大;根长L2、L3的平均根系表面积分别是根长L1的2.28倍和5.17倍;根长L2、L3平均拉拔力分别是根长L1的1.70倍和2.66倍。③ 紫花苜蓿根系拉拔力与植物根径呈负相关,满足幂指函数关系。拉拔强度T的大小为T3 (30~40 cm)>T2 (20~30 cm)>T1 (10~20 cm),根长L2、L3的平均拉拔强度比根长L1的减小了14.70%,53.71%。     

淤积刺激下滨海湿地植物根系吸水及土壤水分变化

基于HYDRUS-1D模型,研究滨海盐沼湿地中泥沙淤积和地下水位对滨海互花米草根系吸水及土壤水分变化的影响。结果表明:地下水位为0 cm时,泥沙淤积对土壤含水率沿土壤深度的分布无影响;地下水位为-14 cm时,互花米草根系生长的土壤含水率相对略低,受到泥沙淤积的轻微影响;地下水位为-28 cm和-42 cm时,泥沙淤积促进互花米草根系吸收土壤表层的水分,加快淤积层土壤水分的消耗,进而改善土壤淤积层的通气条件。在泥沙淤积刺激下,互花米草根系主要吸水区域往淤积层方向垂直上移。     

Partitioning of macroinvertebrate communities in a large New Zealand river highlights the role of multiple shore‐zone habitat types

Bank stabilization is increasing along large rivers as urban areas expand, and the need to protect infrastructure increases in the face of changing climate and flow patterns, but the cumulative effects of different stabilization approaches on reach‐scale biodiversity are not well understood. We investigated physical habitat characteristics and macroinvertebrate community composition and diversity for four shore‐zone habitat types across nested spatial scales over two sampling occasions. Distinct physical conditions were evident for riprap, beach and willow (mixed trees dominated by Salix spp.) habitats, reflecting variations in the combinations of shade, water velocity and substrate size/type, but there was wide variation in habitat conditions for mixed willow‐riprap sites. Additive biodiversity partitioning decomposed reach (γ) diversity into within (α) and among (β₁) sample, among habitat (β₂), and among site (β₃) components, and highlighted significant effects of all spatial scales on macroinvertebrate diversity. Low autumn water levels led to truncated species accumulation curves at beach sites where macrophyte beds that supported macroinvertebrates became stranded, or elevated species accumulation curves for exposed willow‐riprap sites where the river benthos was sampled during hydrological disconnection of bank habitats. Spring and autumn differences in macroinvertebrate community composition were stronger than differences between habitat types. Our findings (a) highlight the interacting effect of river level with shore‐zone habitat function, and (b) underscore the importance of maintaining a diversity of bank habitat types at multiple sites along river shore‐zones to maximize macroinvertebrate diversity.     

深厚软基抛石挤淤加固机理数值模拟研究

抛石挤淤法在沿海高等级公路地基处理中广泛应用,但对加固机理研究较少,通过建立弹塑性有限元力学模型,对抛石挤淤处理的路基应力变形性状进行了分析。计算结果表明:①抛石挤淤处理后的地基能有效提高地基的模量,减小路基沉降和地基浅部水平位移,加速地基孔隙水压力的消散,因此抛石挤淤的加固机理在于人工硬壳层效应和加速排水固结效应;②抛石挤淤体厚度越大,路基沉降越小,而抛石挤淤体模量和宽度对路基沉降的影响较小,因此施工时应采取有效工程措施增大抛石的沉底深度;③填筑速率越大,路基工后沉降越大,预压期越短,路基沉降越大,因此施工时应严格控制施工速度,并保证足够的预压期使路基沉降满足工程要求。深入了解抛石挤淤的加固机理、应力变形性状和影响因素,有助于为设计和施工提供参考和指导。     

Putting down roots: Afforestation and bank cohesion of Icelandic Rivers

Riparian vegetation is widely recognized as a critical component of functioning fluvial systems. Human pressures on woody vegetation including riparian areas have had lasting effects, especially at high latitude. In Iceland, prior to human settlement, native downy birch woodlands covered approximately 15%–40% of the land area compared to 1%–2% today. Afforestation efforts include planting seedlings, protecting native forest remnants, and acquiring land areas as national forests. The planted and protected nature of vegetation along rivers within forests provides a unique opportunity to evaluate the various taxa within riparian zones and the channel stabilizing characteristics of the vegetation used in afforestation. We investigated bank properties, sediment textures, and root characteristics within riparian zones along four rivers in forests in Iceland. Bank sediment textures are dominantly sandy loam overlying coarser textures. Undercut banks are common because of erosion of the less cohesive subsurface layer. Quantitative root data indicate that the woody taxa have greater root densities, rooting depths, and more complex root structures than forbs or graminoids. The native downy birch has the highest root densities, with <1 mm roots most abundant. Modeling of added bank cohesion indicates that willow provides up to six times and birch up to four times more added cohesion to the coarse sediment textures comprising stream banks compared to no vegetation. We conclude that planting and protecting the native birch and willow helps to reduce bank erosion, especially where long-term grazing exclusion can be maintained.     

基于地震映像的河湖水下抛石精准识别方法

基于水下抛石与围岩的波阻抗差异,应用地震波数值模拟软件Tesseral 2-D建立含有水、抛石、填土及基岩的水下抛石模型并对其进行正演模拟。分析了不同震源子波频率和偏移距时的地震响应特征,最终确定震源子波频率为600 Hz,偏移距为5 m的地震数据采集参数。采用一种新型的"轻型气压式浅水域全自动触发器"震源设备对龙河口水库水下抛石进行实际探测。实践表明,地震映像能够识别抛石层的分布范围和厚度,与实际情况吻合的较好。这为利用地震映像法实现对浅水域水下目标体的精确识别提供了重要的理论和实践依据。     

Subsidence of riprap protection without filters for different installation types of riprap around a pier in sands

Synthetic and/or stone filters should be applied to prevent riprap subsidence due to sediment winnowing or leaching between the riprap and sand bed layers when riprap protection is installed around the pier to prevent scour. However, riprap protection without filters is commonly constructed in the field due to the technical and economical difficulties of installing the filter layer. Riprap is also sometimes placed on the bed rather than flush with the bed, especially in the case of deep water and tidal conditions at marine structures. Hydraulic experiments were conducted in this study to quantify and analyze riprap subsidence without filters placed on sand beds for various riprap layer thicknesses, riprap and bed material sizes, riprap installation types, and hydraulic conditions. The experiments showed that, as the flow velocity was increased and the size of bed materials and thickness of the riprap layer were decreased, the subsidence of the riprap protection was increased. A dimensionless riprap subsidence equation was developed using the experimental results for two types of riprap installations (on and below the bed surface). The results of this study can be used to evaluate the subsidence stability of riprap protection without filters.     

动水抛石漂移距离的计算

利用力学分析，导出了抛石在动水中的漂移距离公式，该公式与以往的抛石公式相比，具有3大优点；从理论的角度对抛石的运动机理进行了初步分析，对于进一步深入的理论研究具有参考价值；对于运动中抛石的漂移距离可以列表计算供施工参考应用；通过计算，可以了解抛石的水下运动迹线。     

块石形状尺寸对水平拖曳力系数影响的数值模拟

水平拖曳力系数是研究黄河坝垛水下散抛根石受水流作用的重要力学参数,而水流流速、根石尺寸和根石在水中的仰角对水平拖曳力系数有着不同程度的影响。基于试验数据,应用FLOW-3D数值模拟软件,采用RNG k-ε紊流模型、VOF方法和FAVOR技术模拟水下块体在水流作用下的水平拖曳力。在数值模拟结果验证可靠的前提下,分析块体不同尺寸及其与水流不同夹角对水平拖曳力系数的影响。数值模拟结果表明:当长高比小于等于3.0,水平拖曳力系数随块体长高比增大,先处于波动状态,随后趋于稳定;当长高比大于3.0,水平拖曳力系数随长高比增大而增大;水平拖曳力系数随块体宽高比增大而先增后减,最后保持稳定;水平拖曳力系数随着水流夹角角度增大而先减后增,当夹角为3°时出现最小值。     

河道渠化治理研究

阐述人工裁弯、缩窄河床和固化河岸等河道渠化治理措施对河流的有利和不利影响以及控制渠化河床冲刷下切的措施 (修建拦挡坝、抛石护底、衬砌护底和人工加沙 ) .提出渠化河道设计的两个重要参数─—渠化河宽和平衡比降的确定方法 .介绍美国密西西比河与密苏里河、德国莱茵河和中国涝河的渠化治理     

左江电站岸上抛石护坡施工技术

水下抛石护岸加固是治理江河崩岸的一种常用、易行且有效的防护措施,而将此技术应用于水面以上岸坡防护在国内却是鲜有报道,也无经验可循.本文以左江电站坝下岸坡水上抛石工程施工为例,就该工程的设计、施工及验收等方面进行经验总结,以期为今后的推广和应用提供参考.     

海堤抛石底界的联合探测方法试验研究

如何实现对海堤抛石底界的快速检测是当前水利工程领域研究的热点问题之一。以往主要采用钻孔探测的方法,但施工周期长、成本高且仅一孔之见,故实践中利用该方法难以实现对整个海堤抛石底界的快速检测。鉴于地质雷达方法检测快速且信息连续,提出了地质雷达法与钻孔法进行联合探测的新思路。现场探测试验结果表明,雷达波在抛石体与淤泥层之间存在明显的反射,利用钻孔探测结果对雷达波波速进行标定,可快速有效地实现对海堤抛石底界的整体判定。