柘溪水库拦门沙淤积及治理对策九五优秀科研成果介绍

柘溪水库拦门沙淤积及治理对策研究课题是应电站和库区管理部门的邀请和委托于 1 995年至1 996年间由长沙中南机电技术研究所进行和完成的 ,并以我国优秀科研成果入选《中国九五科学研究成果》丛书 (该成果研究论文在本刊 1 996年第 2期刊出 )。该研究成果首先明确了泥沙淤积是水库运行中五大环境工程地质课题之一 (其他 4个课题为水库渗漏 ,诱发地震 ,库岸变形和矿产淹没 ) ,同时明确了将库尾和各支流入库口的泥沙淤积称为拦门沙 ,提出了对库区泥沙淤积的研究方向。拦河筑坝建立水库 ,使库区的河道落差集中到坝址 ,改变了原来河道的水沙流态和流速 ,引起了河道自然环境变化和河床演变。     

离岸沙坝-潟湖海岸拦门沙航道回淤

渤海湾曹妃甸老龙沟海区属于典型的离岸沙坝-泻湖海岸体系,口门处发育有拦门沙。采用实测资料分析和二维波流泥沙数学模型计算研究了拦门沙成因及其开挖后的回淤情况。研究表明,涨落潮流路不一致、落潮流扩散是老龙沟拦门沙形成的主要原因。针对该海区波浪、潮流、泥沙及海床演变特点,进行了2006年、2007年大小潮潮流泥沙的验证及2008年8~12月试挖槽回淤的验证,在此基础上,预测了拦门沙航道正常情况下的泥沙回淤和大风天骤淤。试挖槽监测资料分析及数学模型计算表明,风浪掀沙是影响老龙沟拦门沙回淤的重要因素。     

离岸沙坝-潟湖海岸拦门沙航道回淤——以渤海湾曹妃甸海域老龙沟拦门沙为例

渤海湾曹妃甸老龙沟海区属于典型的离岸沙坝-潟湖海岸体系,口门处发育有拦门沙。采用实测资料分析和二维波流泥沙数学模型计算研究了拦门沙成因及其开挖后的回淤情况。研究表明,涨落潮流路不一致、落潮流扩散是老龙沟拦门沙形成的主要原因。针对该海区波浪、潮流、泥沙及海床演变特点,进行了2006年、2007年大小潮潮流泥沙的验证及2008年8~12月试挖槽回淤的验证,在此基础上,预测了拦门沙航道正常情况下的泥沙回淤和大风天骤淤。试挖槽监测资料分析及数学模型计算表明,风浪掀沙是影响老龙沟拦门沙回淤的重要因素。     

溪洛渡库区支流拦门沙形成机理

水库蓄水后，水深增加使得河道干支流水动力条件发生改变，干流泥沙倒灌造成支流淤积，影响水库有效库容和航运安全。以溪洛渡水库为例，基于实测资料和三维水沙数学模型，研究库区干流和支流的水沙输移规律，分析支流河口段泥沙淤积特性及拦门沙形成机理。结果表明：(1)库区支流河道淤积泥沙来自支流上游和干流倒灌，其中，支流上游来沙是库区支流河道淤积的主要来源。(2)干流倒灌库区支流河口形成对流和环流区，泥沙易于淤积，西溪河和牛栏江坡度较缓，存在形成拦门沙的风险较大；美姑河坡度较大，存在形成拦门沙的风险较小。(3)对于西溪河、牛栏江和美姑河，干流倒灌的距离随着流量的增加而增加，高水位运行时，水位对干流倒灌的距离影响不明显；而对于金阳河和西苏角河，干流倒灌的距离随着流量的增加基本不变，干流倒灌的距离随着水位的增加而增加。研究成果为新水沙情势下库区支流拦门沙风险防控提供依据。     

金沙江流域水库拦沙效应

水库拦沙是金沙江下游沙量减小的主要原因,对三峡水库的入库水沙条件产生了重要影响。为了系统掌握金沙江流域水库拦沙情况,基于1956年以来流域内水库及实测水沙资料,采用经验公式、典型调查以及输沙平衡原理相结合的方法,对近60年不同阶段金沙江中下游的水库拦沙情况以及水库建设对金沙江流域减沙贡献权重进行了定量研究。结果表明:1956-1990年、1991-2005年和2006-2015年水库拦沙对屏山站的减沙权重分别为0.3%、48%和83%,可见水库拦沙作用逐步增强;1956-2015年,金沙江流域水库年均拦沙0.310亿t,其中大型水库拦沙量占总拦沙量的89%,尤其是2011年以来,随着金沙江中下游以及雅砻江梯级水库群的陆续建成,流域内水库群年均拦沙量达1.92亿t,对屏山站同期年均输沙量的减少权重在90%以上。     

整治工程影响下的河口拦门沙航道回淤特征及成因——以射阳港航道为例

通过不同时期实测地形资料,对比分析射阳港拦门沙航道一期整治工程建设后航道的回淤分布特征;利用实测水文泥沙资料和潮流数学模型计算分析射阳河口拦门沙航道开挖后的水流、含沙量特征;探讨了射阳港拦门沙航道淤积的泥沙来源和淤积成因。研究表明:航道开挖后沿程普遍淤积,尤其是口门及堤根区段航道淤积严重。导致航道淤积的主要原因为:有掩护航道内涨潮流速大、落潮流速小,口门外高含沙量水体进入航道后泥沙很难被带出航道,导致航道内普遍淤积;口门内2 km范围内回淤较大是由于越堤流输沙和口门内侧涨潮期间存在明显回流;导堤根部航道段回淤较大是由于射阳河与黄沙港河汇流后河道放宽,落潮期间出河口的水体挟沙力突然降低。     

三峡水库135m运行阶段永久船闸下引航道泥沙淤积分析

通过实测三峡水库135m运行阶段永久船闸下引航道及口门区泥沙淤积与水沙因子变化,计算分析了下引航道及口门区的淤积量及分布、拦门沙淤积形态、淤积机理及清淤时机,建立了口门含沙量与长江含沙量、口门斜流流速与长江流量、拦门沙淤积高度与来沙量等关系;并结合倒灌异重流理论,计算验证了下引航道及口门区异重流、环流淤积。结果表明,下引航道及口门区主要集中在主汛期(7~9月)淤积,汛末(10~12月)进行一次清淤即可满足航深要求。     

曹妃甸老龙沟潮汐通道拦门沙演变机制

渤海湾曹妃甸老龙沟海区属于泻湖型潮汐通道体系,口门附近发育有大规模拦门沙浅滩。由于沿岸泥沙供给不足,近几十年来东坑坨等沙坝外侧海区整体呈侵蚀冲刷态势,等深线向陆蚀退。老龙沟西支深槽也以侵蚀作用为主,而拦门沙地区滩槽冲淤变化则与东坑坨演变密切相关。其中东槽冲刷发展主要是东坑坨西南尾端淤长压迫老龙沟口门,引起岬角效应增大、潮流动力增强所致,而西槽的摆动现象则主要与东槽发展所产生的挤压作用有关。由于泥沙供给不足,近年来东槽发展和西槽摆动的速度都有明显减缓。     

射阳港双导堤建设环境影响后评价

为治理河口拦门沙,实施了通过整治及疏浚的方式打通拦门沙的射阳港双导堤工程,导堤的功能定位为“导流、挡沙、减淤”。通过对江苏盐城射阳港海岸动力地貌等环境的调查,分析研究射阳港区不同时期的水下沉积物分布特征、不同历史时期的水下地形特征,同时研究不同时期的水质、底质沉积物、生态群落等指标数据,对射阳港双导堤建设的环境影响进行后评价。研究认为：双导堤工程完工后导堤口区域出现明显冲刷,导堤两侧出现淤积,颗粒变细,但对水质环境、底质沉积物环境和生态环境的影响不大,双导堤工程建设对环境影响的风险可控。     

基于GIS的重点区域地质灾害风险评价

为治理河口拦门沙,实施了通过整治及疏浚的方式打通拦门沙的射阳港双导堤工程,导堤的功能定位为“导流、挡沙、减淤”。通过对江苏盐城射阳港海岸动力地貌等环境的调查,分析研究射阳港区不同时期的水下沉积物分布特征、不同历史时期的水下地形特征,同时研究不同时期的水质、底质沉积物、生态群落等指标数据,对射阳港双导堤建设的环境影响进行后评价。研究认为：双导堤工程完工后导堤口区域出现明显冲刷,导堤两侧出现淤积,颗粒变细,但对水质环境、底质沉积物环境和生态环境的影响不大,双导堤工程建设对环境影响的风险可控。     

鄂尔多斯盆地早侏罗世富县期岩相古地理特征

在综合研究钻井剖面、野外露头基础上，结合室内编图、比层对比资料，指出早侏罗世富县期冲积扇－河流相沉积与古地貌密切相关，其古地理格局受印支运动后古构造面上的五条河谷控制；区内存在的冲积扇，分布于深沟河谷的陡壁一侧，为进积型冲积扇；富县期5条河流除晋陕河流为网状砂质河流外，其余均为低弯度砾砂质河流，边滩与洪泛平原微相沉积分布较广，并认为甘陕主河道流向为由西向东，“杂富县”为富县晚期洪泛平原微相产物。     

胜利油田博兴洼陷沙三段高青砂岩体沉积模式研究

为了预测砂体分布规律与岩性圈闭有利区带,指导下一步勘探,采用微观组分特征、岩石结构、粒度分布特征和沉积微相分析等方法,分析研究了高青砂岩体的沉积模式。研究表明,高青砂岩体的沉积微相有水下分流河道、河口砂坝、前缘席状砂沉积、砂泥互层沉积、前扇三角洲深水湖泊沉积。砂岩体的沉积模式分为三种：下部（G3）属（扇）三角洲水下部分沉积,中部（G2）属三角洲水下部分沉积,但湖泊中心和沉积中心进一步向南东方向迁移,上部（G1）与中部相似,但水下主分流河道以向南南东方向展布为主。根据高青砂体所处的构造位置及砂体与围岩的相互关系,确定了砂岩体的沉积环境为扇三角洲前缘与前扇三角洲。     

波浪作用下砂质滩坝的沉积过程与沉积模式

受波浪及沿岸流影响,在滨岸地区形成的滩坝砂体是滨海（湖）带发育的主要砂体类型。目前国内外学者对滩坝沉积砂体的认识多来自于现代沉积和油气地质特征,对滩坝砂体的沉积机制和内部结构研究相对较弱。基于沉积水槽实验,采用规则波浪对沙质斜坡滨岸带进行模拟实验,观测波浪作用下滨岸带滩坝形成过程和波浪运动特征,记录波浪作用下滨岸带沙质滩坝在不同浪带平面时空演化规律。实验结果显示:波浪是改造湖岸原有沉积物的关键驱动力,波浪作用下沙质岸滩床面泥砂将发生输移运动,而滩坝是陆湖（海）泥沙在水动力驱动下搬运沉积的结果,水动力的强弱及水流结构引起泥沙在空间上的不均匀输运和分布,进而塑造不同的滩坝形态。与强波浪相关的高水位可以加速滩坝系统的形成并最终形成大规模的滩坝砂;相比之下,与较弱波浪相关的低水位只能略微改变初始沉积物形态。根据不同的沉积物特征可将实验中的滩坝系统分为三类:冲浪带和碎浪带滩坝系统近端部分的大规模厚层坝砂,破浪带和升浪带滩坝系统中部分布广泛的薄滩砂,以及位于滩坝系统中远端的弧形或平行排列的脊状、砂纹坝砂。建立了水槽实验模式下滩坝沉积模式,可用于指导油气勘探开发。     

Variations in the architecture of hydraulic‐jump bar complexes on non‐eroding beds

Sediment accumulation downstream of hydraulic jumps can occur in many settings but the architectures of such deposits are poorly documented. Here, three flume runs were used to examine the influence of sediment grain size and transport rate on the characteristics of hydraulic‐jump unit bars. In one of these runs six hydraulic‐jump unit bars formed a hydraulic‐jump bar complex. In another, the same sediment was supplied more quickly and only two unit bars formed. In the third run with the same sediment supply rate, but different grain size, only one large unit bar formed. All unit bars developed in a similar way but their size and internal architecture differed; they all resulted from a reduction in sediment transport capacity at the transition from supercritical flow to subcritical flow in the hydraulic jump. After initial onset of sedimentation and unit bar formation, generation of subsequent unit bars may be: (i) related to small changes in sediment flux; and (ii) independent of changes in the hydraulic jump. Continued sedimentation caused changes from oscillating to weak hydraulic jumps and hydraulic‐jump unit bars formed in both circumstances. The flow of water and suspended sediment becomes shallower over the lee of the bar complex. This leads to flow acceleration and a return to supercritical flow conditions. In turn, a chain of such features can form and generate a chute and pool bed morphology. There is an inherent upper size limit to a hydraulic‐jump bar complex due to the changing flow conditions over the growing deposit as the water above it becomes shallower. There is also an amplitude minimum for the development of foresets and subsequent unit bar growth. Hydraulic‐jump unit bars have architectures that should be recognizable in the rock record and because their size is constrained by the flow conditions, their identification should be useful for interpreting palaeoenvironment.     

Interdistributary bay sequences and their genesis

Interdistributary bay sedimentation is dominated by flood-generated incursions from the distributaries. There are three processes by which sediment-laden flood waters can be transferred to the bay: overbank flooding, crevassing and avulsion. These processes combine to produce a family of sedimentary sequences, the majority of which are small-scale coarsening upwards sequences representing infilling of the bay. Subordinate related sequences include those of small-scale (crevasse) channels and larger scale (distributary) channels. Spits or beaches at the mouth of open interdistributary bays produce larger scale, wave-dominated coarsening upwards sequences. A model of bay sedimentation concerning a recently initiated (hypothetical) distributary is presented. Four phases of sedimentation (overbank flooding, crevasse splay, minor mouth bar—crevasse channel couplets and avulsion) characterize the history of the distributary, and it is postulated that the phases are genetically related to alluvial ridge development.     

主要构型要素细分下的曲流河单砂体识别

单砂体的识别始终是曲流河储层描述中重点与难点。构型理论极大地丰富了单砂体描述的方法与内容,然而主要构型要素内部多样的测井相类型与组合特征严重干扰了油藏精细描述的结果。在前人研究的基础上,将Bridge的基础理论简化到油藏描述范畴,简述同一点坝（以及与之相伴生的河道）不同位置下的流体特征与沉积序列,并探讨如何利用测井相组合来识别砂体叠置的6种类型,并应用于油田实践。研究结果表明:1）小层范围内主力砂体内部测井相类型的复杂多变反应了沉积过程中复杂的水动力特征,由于环绕单一点坝砂体的最大流速靠近坝头一侧而远离坝尾一侧,使得坝头以箱型韵律为主,坝尾以钟形韵律为主,并以此作为油藏描述中刻画点坝展布的理论基础;2）在研究砂体叠置类型的过程中,可以根据剖面上测井曲线的变化情况来识别砂体的不同部位和不同拼接方式,从而建立更为精确的砂体叠置样式类型;3）该理论与露头调研的吻合度较高,在储层应用过程中,在曲流段保存相对完整的层段有着良好的应用效果。     

Recent, arctic deltaic sedimentation: Olivier Islands, Mackenzie Delta, North-west Territories, Canada

Despite a low tidal range and relatively low wave conditions, the Mackenzie Delta is not prograding seaward but rather is undergoing transgressive shoreface erosion and drowning of distributary channel mouths. In the Olivier Islands region of the Mackenzie Delta the resultant morphology consists of a network of primary and secondary channels separated by vegetated islands. New ground is formed through channel infilling and landward-directed bar accretion. This sedimentation is characterized by seven sedimentary facies: (1) hard, cohesive silty clay at the base of primary channels which may be related to earlier, offshore deposition; (2) ripple laminated sand beds, believed to be channel-fill deposits; (3) ripple laminated sand and silt, interpreted as flood-stage subaqueous bar deposits; (4) ripple laminated or wavy bedded sand, silt and clay, representing the abandonment phase of channel-fill deposits and lateral subaqueous bar deposition from suspension settling; (5) a well sorted very fine sand bed, presumed to result from a single storm event; (6) parallel or wavy beds of rooted silt, sand and clay, interpreted as lower energy emergent bar deposits; and (7) parallel or wavy beds of rooted silt and clay, believed to represent present-day subaerial bar aggradation. The distribution of sedimentary facies can be interpreted in terms of the morphological evolution of the study area. Initial bar deposition of facies 3 and channel deposition of facies 2 was followed by lateral and upstream bar sedimentation of facies 3 and 4 which culminated with the deposition of the storm bed of facies 5. Facies 6 and 7 signify bar stabilization and abandonment. Patterned ground formed by thermal contraction and preserved in sediments as small, v-shaped sand wedges provides the most direct sedimentological indicator of the arctic climate. However, winter ice and permafrost also govern the stratigraphic development of interchannel and channel-mouth deposits. Ice cover confines flow at primary channel mouths, promoting the bypassing of sediments across the delta front during peak discharge in the spring. Permafrost minimizes consolidation subsidence and accommodation in the nearshore, further enhancing sediment bypass. Storms limit the seaward extent of bar development and promote a distinctive pattern of upstream and lateral island growth. The effects of these controls are reflected in the vertical distribution of facies in the Olivier Islands. The sedimentary succession differs markedly from that of a low-latitude delta.     

渤海海域沙一二段混合沉积分布特征与勘探实践

渤海海域广泛发育陆源碎屑与碳酸盐矿物的混合沉积,随着近年来混积型储层的油气勘探相继获得重要发现,混合沉积分布规律亟待深入研究.基于大量基础资料,对渤海海域古近系混合沉积进行了系统性的分析,明确了其时空分布特征,完善了混合沉积相关地质认识.渤海海域古近系沙一二段（E₂s_1-2）主要发育以陆源碎屑为主的混积岩、以生物成因碳酸盐矿物为主的混积岩以及以化学成因碳酸盐矿物为主的混积岩三大类岩石类型.受控于干旱的气候与较高盐度的水体条件,混合沉积主要发育于沙一二段沉积时期,在空间上远离区域物源体系,主要围绕盆内局部凸起分布,低凸起、凸起倾末端、近岸隆起、远岸隆起等正向的水下古地貌单元是混合沉积发育的有利部位.根据发育位置、古地貌背景、与陆源碎屑供给的关系等古地理要素,混合沉积成因样式可分为近岸混积扇三角洲、近岸扇体侧翼混积滩坝、近岸隆起混积滩坝、远岸隆起混积滩坝4种类型及六亚类.近岸混积扇三角洲、近岸扇体侧翼混积生屑滩坝、近岸隆起混积碎屑滩坝、远岸潜山隆起混积生屑滩坝4种具体类型的混合沉积物产出规模与厚度较大,易形成粒度粗、生屑含量高、杂基含量少、白云石化作用发育、物性条件较好、产能较高的优质储层,是较为有利的勘探类型.上述地质认识有效地指导了一批混积型储层的重大勘探发现,揭示了混合沉积领域巨大的勘探潜力,对渤海海域中深层勘探具有重要的推动意义.      

Tidal currents and wind waves controlling sediment distribution in a subtidal point bar of the Venice Lagoon (Italy)

The present study aims to improve current understanding of the sedimentation of subtidal point bars, analyzing interaction between tidal currents and waves in shaping a submerged meander bend of the microtidal Venice Lagoon (Italy), and it is based on coupling of sedimentological studies, geophysical analyses and numerical modelling. The Venice Lagoon is characterized by an average depth of about 1·5 m over subtidal platforms and a mean tidal range of about 1·0 m. The morphodynamic evolution of the lagoon is strongly affected by intense seasonal windstorms, which promote the formation of wind waves triggering sediment resuspension and bottom erosion. The study channel is 70 to 100 m wide, it has a radius of curvature of about 260 m and cuts through a permanently submerged subtidal platform. Water depth ranges from 1·0 to 5·0 m below mean sea level on the subtidal platform and channel thalweg, respectively. Different from classical architectural models, the study point‐bar beds do not show sigmoidal geometries, but consist of horizontally‐bedded deposits abruptly overlying clinostratified beds. Sedimentation in the study bar is hypothesized to stem from the interaction between the in‐channel secondary helical flow, as for most meander bends, and wave winnowing of the subaqueous overbank areas. Laterally accreting point‐bar deposits point out that the curvature‐induced helical flow redistributed sediment from the channel thalweg to the bar top and contributed to the development of the ‘classical’ fining‐upward grain size trend. The marked truncation surface, separating clinostratified bar deposits from overlying horizontally‐bedded platform sediments is interpreted here as due to bar top wave‐winnowing, which also possibly promoted bank collapses. In the proposed model, sediments remobilized from bar top and subaqueous overbank areas were transported into the channel, forming peculiar ‘apron‐like’ accumulations, where sand accumulated through avalanching processes and mud settled down from suspension.     

Sedimentary environments and trace fossils of the Permian Snapper Point Formation,Southern Sydney Basin

The Lower Permian Snapper Point Formation at its type locality in the southern Sydney Basin is interpreted as a regressive sequence of a linear clastic shoreline. Lithologies, sedimentary structures, and palaeocurrent patterns suggest a prograding barrier‐beach environment. Barrier foot, bar nucleus, bar crest, and back‐bar are distinguished. Abundant trace fossils aid the recognition of minor facies. The thickness of sediments deposited in the protected inshore environment may be explained by progradation into rising relative sealevel, but rates of sealevel rise or land subsidence were ultimately exceeded by the rate of sediment supply. Up‐sequence changes in the character of the sedimentation units and biofacies may therefore reflect an evolution from a barrier profile to an open mainland beach.