A soft soil treatment technology combining tidal energy and vacuum preloading is proposed in this paper to achieve green municipal construction, energy saving and emission reduction, also to support the national strategic goals of “Carbon Peak and Carbon Neutrality”. This technology making full use of the tidal energy as the preloading with low frequency cyclic load, together with the constant vacuum preloading, enables the soft soil to be drained and consolidated by cyclic compressive stress, accelerates the dissipation of pore water pressure between soil particles, enhances soil compaction, and induces horizontal creep in the soil between prefabricated vertical drain. Consequently, the bearing capacity and stability of the foundation are improved while reducing rebound settlement. Model tests demonstrate that this technology enhances foundation bearing capacity, eliminates most rebound settlement, shortens construction periods, and reduces costs. Based on tidal characteristics, a practical solution using the principle of communicating vessels is proposed to apply tidal energy for soft soil treatment in coastal areas. A research- to-application transformation scheme is also outlined.
Stator asymmetric-paths winding of variable speed pump storage (VSPS) generator-motor can solve the problem of mismatch of unit speed, capacity and outlet voltage. However, different winding connection schemes will lead to the change of magnetomotive force (MMF) asymmetry of each branch, and then affect the electromagnetic force of generator-motor. In order to explore the effect of this winding type on the electromagnetic force, stator asymmetric-paths winding's MMF and electromagnetic force of 336 MW VSPS generator-motor is derived. Waveforms and harmonic contents of the stator asymmetric-paths winding MMF of the equal-pitch and unequal-pitch schemes are analyzed. Under the consideration constraints of factors such as minimizing MMF asymmetry and electromagnetic vibration, a reasonable asymmetric-paths winding scheme with unequal pitch is determined It is concluded that asymmetric-paths winding scheme with pitch of 14-15-16 can effectively weaken the low-order MMF harmonics and reduce the electromagnetic force under the limitation of asymmetric-paths winding form. The finite element model of VSPS generator-motor is further developed, and the electromagnetic force amplitude and spatial and temporal distribution characteristics under 6 winding schemes are calculated to verify the accuracy of the calculation model. The results of the study can provide technical support for the development of localized VSPS generator-motor.
Aiming at the nonlinear characteristics of synchronous reluctance motor(SynRM)caused by electromag-netic saturation and cross coupling of stator inductance,a position sensorless control method combining recursive least square method and pulse vibration high frequency current signal injection was proposed.The principle is to inject high fre-quency sinusoidal current signals with fixed amplitude into the direct axis of synchronous reluctance motor observation co-ordinate system,and extract voltage signals containing rotor position information from the quadrature axis.The recursive least square method with forgetting factor is used to realize the online identification of the motor resistance and inductance parameters.The position sensorless control of motor is realized by proper signal processing method.The simulation and prototype experiments are carried out to verify the accuracy and practicability of the proposed method.
The objective of this study is to discuss the hydrodynamic performance of a wave energy converter using floating panels. A scale model was built in the laboratory at Hohai University, and then was employed to investigate the performance of developed wave energy device. In the physical model, the water surface fluctuation, motion of floating panels and the voltage output of the dynamos are simultaneously measured. Wave reflection coefficient and the energy output can be estimated directly using these measurements. Experimental results show that the present device is effective in controlling the wave energy and reducing the threat to the coastal area. When subjected to longer waves, the average output power and conversion efficiency of the WEC can be up to 0.65 W and 2.73%, respectively. Moreover, it is found that the load of the energy device should be carefully designed to match the local wave climate, in order to obtain the best energy conversion efficiency.
Aiming at the problem that the mechanical properties of mica quartz schist are easy to deteriorate under dry-wet cycles， taking the mica quartz schist which widely distributed in Shiyan， Hubei Province as the research object， uniaxial compression test and electron microscope scanning test were carried out on mica quartz schist samples under different dry-wet cycles to reveal the law and mechanism of mechanical property degradation. The results showed that under the action of dry-wet cycles， the degradation effect of compressive strength and elastic modulus of mica quartz schist were obvious， the degradation rate was fast and the degradation range was large in the early stage， and the degradation rate was slow and the degradation range was low in the later stage. The macroscopic failure modes were gradually controlled by the schistosity planes， which gradually evolved from styles of "X" and "Y" failure to along the schistosity planes failure. The microstructure was characterized by continuous spalling and granulation of flake mineral particles， and the micro cracks and pores were gradually developed， expanded and connected. The mica quartz schist produce secondary minerals， ions and rock cuttings and leave the rock continuously under the dry-wet cycles which promotes the preferential expansion and cracking of schistosity， microcracks and other structural planes， and then degrades the overall mechanical properties of the mica quartz schist.
为探究水胶比、粉煤灰、矿粉掺量、龄期对全风积沙混凝土抗压强度的影响,开展了全风积沙混凝土抗压强度试验,结合XRD衍射结果对其物象成分进行微观表征,并通过多元线性回归建立全风积沙混凝土抗压强度预测模型.结果表明,全风积沙混凝土抗压强度随水胶比增大先增加后减小,当水胶比为0.4时,抗压强度最大;粉煤灰对全风积沙混凝土抗压强度增长效应不及矿粉增长效应显著;粉煤灰和矿粉的掺入更易将AFt转化为AFm;建立的抗压强度预测模型精度较高,适用于细砂混凝土.研究结果可为全风积沙混凝土的工程应用提供理论依据和技术支持.
深井降水会导致地下水位下降、降低土体强度和稳定性,从而影响引水隧洞施工安全.为研究深井降水对施工期隧洞渗流场的影响,以西霞院水利枢纽输水及灌区工程穿沁隧洞为依托,建立了该隧洞三维渗流有限元计算模型,考虑隧洞施工计划和沁河水位变化,分析了深井降水和未降水情况下隧洞渗流特性.结果表明,深井降水会对隧洞开挖产生影响,使深井周围渗流场位势分布特征发生改变,浸润面形成降落漏斗,水位等值线在深井附近呈回水环状.深井降水相较于深井未降水时的最大渗透坡降、单宽渗透流量分别增加了18.6、3.3倍,各工况下土层渗透稳定均满足要求.研究成果可为类似引调水工程的设计和施工提供参考依据.
The Downstream Surge Chamber of a pumped storage power station adopts impedance with an upper chamber layout. The tailrace tunnel is connected with the connecting pipe through a right-angle bifurcated pipe and bend. The layout type is special and the water flow conditions are complex. To study its hydraulic characteristics, a three-dimensional flow field mathematical model of the connecting pipe at the bottom of the surge chamber is established, and the variation law of hydraulic characteristics under different diversion ratios and confluence ratios is studied. The results show that for the resistance loss of the surge chamber with the complex bottom flow, the three-dimensional numerical simulation can achieve a better simulation effect, and the calculation results are in good agreement with the theoretical analysis results. Because the elbow is at the bottom of the surge chamber, the sudden expansion and contraction between the connecting pipe and the big well will cause additional hydraulic losses, its head loss coefficient is greater than that of the conventional impedance surge chamber, and the flow coefficient is smaller than that of the separate impedance hole.
鉴于复合床面条件下刚性非淹没植物改变推移质输沙特性的相关研究成果较少,为此采用水槽试验和理论分析方法,研究了平行排列的刚性非淹没植物对泥沙起动谢尔兹数和推移质输沙强度的影响.结果表明,平行排列的刚性非淹没植物使得泥沙起动谢尔兹数增大了 97.2％,推移质输沙率降低了 80％以上.通过理论分析提出了适用于刚性非淹没植物平行排列条件下恩格隆推移质输沙率公式,经验证该公式具有较高的精确度.
平原区河网尤其在机场处具有复杂的水文结构,防洪排涝工作至关重要.以杭州萧山机场为例,采用MIKE11构建一维河网水动力模型,通过已有排水泵站的不同开启工况分析其排涝现状,并针对其现状提出相应的优化提升方案.结果表明,杭州萧山机场西工作区现状整体排涝能力达不到20年一遇标准.在排涝优化提升方面,建议使用强排换调蓄,采用"强排为主,调蓄结合"的排涝思路,形成"骨干河道+强排泵站"的排涝总体格局.
为提升岷江水资源分配效益及合理性,从水资源管理及考核成效角度入手,建立包括取用水监管率、控制断面水质达标率和下泄流量预警等指标在内的水量分配指标体系,采用主客观结合的综合赋权法定量计算各取水城市取水量,并分析各指标的重要性.结果表明,取水量分配结果与实际分水结果在排序上总体一致,岷江中游成都、眉山等城市对水资源需求量较大,可为岷江水资源调度与水权交易提供依据;取用水监管率与控制断面水质达标率在6个新指标中权重较大,对推动构建新的水量分配指标体系提供了一种思路.分水结果兼顾了河流健康与水环境要求,同时将水资源管理效益与分水直接挂钩,可为实际分水提供参考,并促使各地区有侧重地持续做好水资源管理及考核相关工作.
特高压直流穿墙套管是我国电网的卡脖子技术之一.目前不仅其核心设计与制造技术存在较多难点有待攻克,其设备运行的状态监测技术也是一个难点问题.为此,在分析特高压直流穿墙套管的结构和常见故障的基础上,探索了振动法在特高压直流穿墙套管故障在线监测领域的应用,并开展了理论仿真研究,发现当特高压直流穿墙套管的外绝缘或内绝缘发生损伤时,套管的基础特征频率有明显改变.随后对800 kV级特高压直流穿墙套管的电容芯子开裂和硅橡胶伞裙破裂开展了故障模拟和振动测试,结果表明不同故障状态下套管的基础特征频率有较大差异.因此采用振动监测技术可有效实现对特高压直流穿墙套管故障的甄别,可为特高压工程建设和运维人员提供技术参考.
由于隧洞塌方风险评价涉及众多模糊因素且评价方法复杂,因而造就了评价体系构成灰色体系、评价方法适用性不高、难以准确评估隧洞塌方风险等级的问题.基于此,运用灰色系统基本思想及矢量投影原理,提出了一套基于灰色矢量投影法的隧洞塌方风险评价模型,在综合分析复杂地层条件下隧洞塌方的影响因素基础上,采取顾及到决策者观点差异程度的群层次分析法(GAHP)对预选评价指标体系进行降维遴选,继而根据综合决策权重系数遴选出能够充分反映塌方机理迥异、具有代表性和区分度高的13个优选评价指标,在此基础上建立隧洞塌方风险优选评价指标体系;此外,引入灰色群组聚类(GGC)和反熵权法(AEW)分别确定主、客观单层次排序权重;利用改进博弈论组合赋权(ICWGT)获得最佳综合权重分配系数,确定指标总层次排序权重;最后根据此模型对隧洞塌方风险进行评估验证.研究结果表明,隧洞塌方风险评价等级与实际开挖情况吻合度较高,验证了该模型的可靠性及准确性.
随着投产时间的推移,水电站轴承油槽盖密封被逐渐磨损,动静配合间隙增大,油雾逸出现象严重.为了探究磨损间隙和机组转速对油槽密封处油雾泄露的影响,建立了发电机推力轴承油槽密封几何模型,应用SST κ-ω湍流模型,对不同间隙(0.2～2.0 mm)、不同转速(100～500 r/min)下油雾的泄露情况进行稳态数值模拟计算.结果表明,建立泄漏量、间隙值及转速三者之间的函数关系表达式,可发现间隙值对油雾泄漏量的影响比转速高;间隙增加后,密封齿的节流作用减弱,密封进口压力降低,加剧了油槽盖顶部的油雾泄露;进、出口处的流速随间隙值的增加而增大,当间隙值由0.2 mm增加至2.0 mm时,进口速度由20 m/s增加到113 m/s,出口速度由76 m/s增加到144 m/s,泄漏量由0.034 4 kg/s增加到0.053 8 kg/s.该研究可为水电站轴承油槽密封结构的优化、电站运行策略的制定及密封性能的判断提供一定的理论基础.
为解决传统裂缝三向检测方法成本高、效率低的问题,提出了一种基于双目视觉的裂缝三向变化检测方法.首先建立裂缝三维等效模型,将裂缝变化计算等效为计算标靶间变化情况;然后通过特征点编码匹配、空间坐标系变换、三维坐标计算等对裂缝进行三维重建,量化裂缝三向变化情况;最后通过单轴位移试验验证了该方法的精度.结果表明,裂缝的开合方向和平行于裂缝表面的错动方向最大测量误差在0.2 mm以内,垂直于裂缝表面的错动方向的最大测量绝对误差在0.3 mm以内,满足《土石坝安全监测技术规范》中对于裂缝检测的要求.
导流隧洞作为泄水建筑物,洞身、洞顶和底板的压力分布对于避免空蚀空化、振动等不良现象至关重要.以叶巴滩水电站导流隧洞为例,基于物理模型试验、RNG κ-ω紊流模型、VOF法建立的三维数值模型模拟了导流隧洞压力分布,通过泄流能力、底板沿程压力等试验数据验证了数值模型的可靠性.结果表明,导流隧洞底板和顶部沿程压力分布均呈下降趋势,但在闸室段、堵头段等水力边界突变处,压力值发生了波动;在转弯段,水流受离心力影响显著,主流区位置和水流压力存在偏离轴线,靠近外边墙的趋势.
为研究长江口拦门沙段重要滩涂对水沙条件改变及人类活动的响应机制,以横沙浅滩、九段沙及南汇东滩为例,分析了拦门沙段重要滩涂的平面形态调整特点及其对环境因素变化的响应过程,并建立了代表滩涂面积与汛期水沙条件间的经验关系.结果表明,横沙浅滩、九段沙及南汇东滩近年来滩涂平面形态呈萎缩态势、沙尾总体滞涨,且横沙浅滩及九段沙有不同程度的串沟发育现象;横沙浅滩面积与前7年平均的汛期水流冲刷强度具有良好的幂函数关系,反映了浅滩面积随水沙条件变化的滞后响应过程;河口治理工程对滩涂局部的守护能较快抑制水沙条件改变所引起的冲刷,但其对周边区域可能产生缓慢、长期的累积影响.
为研究水工混凝土材料在冻融循环与盐侵蚀耦合作用下构件性能演变规律,选取不同引气剂掺量(0、0.005％、0.01％)的早期受冻试件,置于质量分数为3.5％氯化钠+5％硫酸钠复合溶液内进行冻融循环试验,并基于核磁共振技术(NMR)—分形理论,构建混凝土孔体积分形维数与试件抗压强度间的耦联关系.结果表明,在混凝土材料中适量加入引气剂,可有效提高盐冻作用下构件的弹性模量、抗压强度等力学性能,并可改善孔结构,提高抗冻性;核磁共振测试的混凝土孔体积分形维数随着冻融循环次数的增加逐渐减小,表明引气剂的加入可改变初始状态下混凝土内部孔隙结构,且随着引气剂掺量的增加效果更为明显;结合分形理论建立的孔体积分形维数与抗压强度关联模型,发现分形维数DMAX与抗压强度的最佳函数关系近似指数函数,回归系数R2均大于0.85,拟合效果良好,可为混凝土结构的耐久性评估提供参考.
针对利用马卡维耶夫法计算造床流量繁琐的问题,采用地貌功图解法简化计算造床流量,并基于黄河下游花园口、高村、艾山、利津4个水文站1960～2014年实测水沙数据,通过马卡维耶夫法与地貌功图解法分别计算4站历年造床流量.结果表明,两种方法所计算的黄河下游4站历年造床流量差异较小且下降趋势相近,地貌功图解法相比马卡维耶夫法计算造床流量更简便、准确.
为提高枯水期南昌市水环境承载力,构建了赣江尾闾水环境数学模型,研究了不同水文条件的优化调度方案.结果表明,在流量小于1 020 m3/s时,赣江主干河流和下游主、北、中、南四个分支最佳调度水位在最低生态水位和警戒调控水位之间,调度时间在1.11 d以内;在流量大于1 020 m3/s后时,警戒调控水位即为防洪限制水位,主干河流和四个分支的最佳调度水位在最低生态水位和防洪限制水位之间,调度时间在4～7 d内.建议各分支拦河枢纽靠近警戒调控水位运行,既能保证河流控制断面水质达标,又能最大限度的保持南昌市水资源可利用量.
