Application of strength reduction method to dynamic anti-sliding stability analysis of high gravity dam with complex dam foundation

Considering that there are some limitations in analyzing the anti-sliding seismic stability of dam-foundation systems with the traditional pseudo-static method and response spectrum method, the dynamic strength reduction method was used to study the deep anti-sliding stability of a high gravity dam with a complex dam foundation in response to strong earthquake-induced ground action. Based on static anti-sliding stability analysis of the dam foundation undertaken by decreasing the shear strength parameters of the rock mass in equal proportion, the seismic time history analysis was carried out. The proposed instability criterion for the dynamic strength reduction method was that the peak values of dynamic displacements and plastic strain energy change suddenly with the increase of the strength reduction factor. The elasto-plastic behavior of the dam foundation was idealized using the Drucker-Prager yield criterion based on the associated flow rule assumption. The result of elasto-plastic time history analysis of an overflow dam monolith based on the dynamic strength reduction method was compared with that of the dynamic linear elastic analysis, and the reliability of elasto-plastic time history analysis was confirmed. The results also show that the safety factors of the dam-foundation system in the static and dynamic cases are 3.25 and 3.0, respectively, and that the F2 fault has a significant influence on the anti-sliding stability of the high gravity dam. It is also concluded that the proposed instability criterion for the dynamic strength reduction method is feasible.

Sensitivity analysis of factors affecting gravity dam anti-sliding stability along a foundation surface using Sobol method

The anti-sliding stability of a gravity dam along its foundation surface is a key problem in the design of gravity dams.In this study,a sensitivity analysis framework was proposed for investigating the factors affecting gravity dam anti-sliding stability along the foundation surface.According to the design specifications,the loads and factors affecting the stability of a gravity dam were comprehensively selected.Afterwards,the sensitivity of the factors was preliminarily analyzed using the Sobol method with Latin hypercube sampling.Then,the results of the sensitivity analysis were verified with those obtained using the Garson method.Finally,the effects of different sampling methods,probability distribution types of factor samples,and ranges of factor values on the analysis results were evaluated.A case study of a typical gravity dam in Yunnan Province of China showed that the dominant factors affecting the gravity dam anti-sliding stability were the anti-shear cohesion,upstream and downstream water levels,anti-shear friction coefficient,uplift pressure reduction coefficient,concrete density,and silt height.Choice of sampling methods showed no significant effect,but the probability distribution type and the range of factor values greatly affected the analysis results.Therefore,these two elements should be sufficiently considered to improve the reliability of the dam anti-sliding stability analysis.

Interval finite element method and its application on anti-slide stability analysis

The problem of interval correlation results in interval extension is discussed by the relationship of interval-valued functions and real-valued functions. The methods of reducing interval extension are given. Based on the ideas of the paper, the formulas of sub-interval perturbed finite element method based on the elements are given. The sub-interval amount is discussed and the approximate computation formula is given. At the same time, the computational precision is discussed and some measures of improving computational efficiency are given. Finally, based on sub-interval perturbed finite element method and anti-slide stability analysis method, the formula for computing the bounds of stability factor is given. It provides a basis for estimating and evaluating reasonably anti-slide stability of structures.

Stability analysis of concrete gravity dam on complicated foundation with multiple slide planes

A key problem in gravity dam design is providing enough stability to prevent slide, and the difficulty increases if there are several weak structural planes in the dam foundation. Overload and material weakening were taken into account, and a .finite difference strength reserve method with partial safety factors based on the reliability method was developed and used to study the anti-slide stability of a concrete gravity dam on a complicated foundation with multiple slide planes. Possible slide paths were obtained, and the stability of the foundation with possible failure planes was evaluated through analysis of the stress distribution characteristics. The results reveal the mechanism and process of sliding due to weak structural planes and their deformations, and provide a reference for anti-slide stability analysis of gravity dams in complicated geological conditions.

Interface stress element method and its application in analysis of anti-sliding stability of gravity dam

The rigid body limit equilibrium method （LEM） and the nonlinear finite element method （NFEM） are often used in the analysis of anti-sliding stability of gravity dam. But LEM cannot reflect the process of progressive instability and mechanical mecha- nism on failure for rock mass while NFEM is difficult to use to solve the displacement discontinuity of weak structural plane. Combining the research with Xiangjiaba Hydropower Station project, the analysis of anti-sliding stability for segment 12# of the dam has been carried out using interface stress element method （ISEM）. The results can reflect the most dangerous location, the scope and distribution of failure zone in weak structural plane, and present the process of progressive failure in dam foun- dation as well as the safety coefficient of possible sliding body. These achievements provide an important technical reference for dam foundation treatment measures. The computational results show that ISEM can naturally describe discontinuous de- formation of rock mass such as dislocation, openness and sliding. Besides, this method is characterized by good adaptability, convenient calculation and high compatibility, thus it is regarded as an effective way to make an analysis of anti-sliding stabil- ity of gravity dam

变体飞行器的气动与多学科设计需求

变体飞行器可以通过局部或整体变形来改变飞行器的外部形状,实时适应多种任务需求,在多种飞行环境下保持气动性能最优,已经成为21世纪航空航天领域的前沿研究热点。本文首先梳理了变体飞行器的气动与总体设计、结构、控制、噪声、隐身之间的联系,然后针对变体飞行器气动设计面临的任务需求,阐述了增升减阻、稳定性和操纵性、降低气动噪声以及增强飞行器隐身性等气动与多学科设计对不同变形方式的需求,最后对变体飞行器关键技术和未来发展方向进行了展望,为变体飞行器气动与多学科设计的发展提供参考。

基于大变形升阻锚索深埋巷道围岩稳定性控制研究

研发了一种新型大变形升阻锚索支护结构,通过串联6个壁厚5 mm含环形V槽的直管型钢结构实现锚索吸能让压,吸能率为44.55 J/g。拉拔试验结果表明新型锚索极限变形量(221.58 mm)与普通传统锚索相比增加了4.87倍,具有大变形、增阻及高吸能等优良性能。通过离散元UDEC程序的二次开发,模拟了新型大变形增阻锚索支护阻力−变形曲线的双弹性阶段。采用新型锚索对深埋巷道围岩支护效果数值模拟结果表明,与无支护及传统锚索支护相比,顶板下沉量分别减小了88.33%与74.64%,稳定状态下最大主应力峰值分别减小了23.15%与18.34%,塑性区厚度分别减小了37.50%与62.50%。最后将新型大变形增阻锚索成功应用于真实巷道,两帮最大收敛变形量约为300 mm,实现了较好的支护效果。

规模化储能虚拟同步控制策略及其惯量分析

高比例电力电子设备无法为系统提供足够惯量,给电力系统带来巨大的挑战。虚拟同步发电机(virtual synchronous generator,VSG)控制的储能系统可以参与电网频率调整,提高频率稳定性。重点分析VSG控制参数对含规模化储能的多节点系统的稳定性和惯量支撑能力的影响,给出规模化储能在不同系统惯量水平下控制参数的配置依据。首先,介绍VSG控制的原理和实现方式,并建立系统的状态空间模型。其次,分析同步电机的惯量响应过程,推导频率扰动事件下VSG需要提供的能量及对应的虚拟惯性时间常数。然后,建立含VSG控制储能的3机9节点系统仿真模型,利用模态分析法分析控制参数对系统稳定性的影响。最后,通过仿真验证储能的惯性支撑能力以及储能参数配置原则的有效性。

百米级填埋场扩建增容方法与实践--以成都某填埋场为例

土地资源紧张,很难新征用地新建填埋场,扩建增容成为解决库容不足的重要手段。本研究提出了填埋场扩建增容设计思路,基于现场监测和堆体稳定分析判定扩建增容的可行性,提出不同库容增加量的工艺比选方案,开展各方案的增容堆体稳定性验算,并结合稳定控制措施要求、投资等因素确定扩建增容方案。以成都某填埋场为例,现状堆体整体稳定安全系数为1.794~1.881,具备扩建增容的可行性。工艺比选方案一增容量为1.2×10^(6) m^(3),扩建增容后堆体整体稳定安全系数为1.481~1.713;工艺比选方案二增容量为8.0×10^(5)m^(3),扩建增容后堆体整体稳定安全系数为1.696~1.784。采取了妥善的稳定控制措施后最终选定工艺比选方案一。

吉林油田页岩油水平井二开钻井关键技术及应用

吉林油田页岩油主要位于松辽盆地南部长岭凹陷,已经完钻5口纯页岩水平井。由于目的层层理和裂缝发育,造成井壁稳定性差,在施工过程中,存在返砂效率低、井壁易坍塌、水平段延伸困难、摩阻扭矩大等技术难题。针对这些问题,通过井身结构优化、强封堵钻井液应用、高效PDC钻头及提速工具优选、井筒清洁参数优化及压力精确控制等技术攻关,形成页岩油二开长水平段水平井钻井关键技术。应用结果表明:①采用强抑制强封堵高性能油基钻井液能有效封堵裂缝,大幅降低钻井液侵入量,并有效防止页岩膨胀,提高井壁的化学稳定性;②钻井液排量大于38 L/s、顶驱转速大于80 r/min能够保持水平井井筒清洁,节约短起下钻及下套管前通井的时间3 d以上;③个性化PDC钻头配合旋导施工能大幅度提高机械钻速,使井壁浸泡时间缩短30%以上。优化起钻速度使井底压力波动降低52%,进一步提高井壁稳定性;④吉林油田页岩油水平井由三开井身结构简化为二开井身结构,水平段长度提高82.75%,机械钻速提高53.73%,钻井成本降低33%。

伊敏露天煤矿内排土场边坡稳定性研究

为研究伊敏露天矿内排土场增高扩容的可行性,需定量地研究内排土场边坡的稳定性。采用了工程地质勘查手段,获取了地层岩性的空间分布规律,建立了典型工程地质剖面,根据物理测井成果,对地质剖面进行了校准;运用了物理测井法、岩土物理力学试验法及强度折减公式,综合确定了岩土体物理力学指标推荐值;采用了有限差分方法,研究了内排土场边坡的潜在变形破坏模式。结果表明:内排土场整体边坡为“圆弧剪切+顺层滑移”的潜在变形破坏模式,内排土场整体边坡处于稳定状态,边坡安全储备系数满足煤炭工业露天矿设计规范要求。

我国气田采出水处置面临的关键挑战与对策建议

气田采出水的低成本安全高效处置已成为制约我国天然气稳产增产的主要因素,解决气田开发水处置难题对保障国家能源安全具有重要意义。基于对我国陆上四大含油气盆地中主要气田产水现状的梳理,分析了我国气田采出水处置面临的关键挑战,提出了解决气田采出水处置难题的对策建议。研究表明,分布于我国鄂尔多斯盆地、塔里木盆地、四川盆地以及柴达木盆地的气田多数面临气水同采、产水激增的状况。“双碳”战略目标下,气田采出水面临产水量逐年增加、国家层面回注管理制度与标准规范缺失、地表达标外排成本高且适用地区有限、综合资源化利用尚处起步阶段等关键挑战。需加强气藏整体治水研究,健全国家层面气田采出水回注管理与技术标准体系,推进气田采出水低成本综合资源化利用,拓展气田采出水处置新路径。我国气藏类型多样,地质地貌水文气候条件复杂多变,需因地制宜推进气田采出水的回注处置、达标外排与综合资源化利用,多措并举支撑我国“稳油增气”与“双碳”战略目标实现。

不同采集水头对灯泡贯流式机组运行工况的影响分析

在保证电站安全稳定运行的基础上,对某电站1号机组开展基于毛水头、净水头的优化运行性能分析。通过对比低水头、高水头条件下的机组有功、协联关系、主要稳定性数据,从而评价机组在哪类设置水头具有更优的综合经济效益,以便后期指导机组开展水头采集优化的提质增效工作。

大城县大豆玉米带状复合种植技术

推广大豆玉米带状复合种植,力争玉米单产与清种基本相当,尽可能增加大豆产量,集成创新适合大城县的大豆玉米带状复合种植技术模式,实现作物带间轮作,改良土壤结构,减少病虫发生,降低化肥农药使用量。

提速条件下粉土铁路路基动态稳定性研究

路基的动态响应及稳定直接决定了提速列车运行的舒适度和安全性。通过室内循环三轴试验,模拟了路基在湿度变化与提速列车动荷载作用下的动态特性。根据试验结果,结合既有线提速路基的动应力变化规律发现:在最优含水率附近,当压实系数为0.90,提速情况下路基可保持稳定状态;若压实系数为0.85,在动应力不超过70 kPa时,路基稳定性较好,但随着动应力水平增加和加载频率增大,路基的累积变形加剧并产生动强度破坏。列车提速使路基的弹性变形增大,但对路基的回弹模量影响较小。路基湿度增加导致临界动应力、回弹模量显著降低,而回弹应变、循环累积应变迅速增加,有可能导致路基产生动强度破坏,因此,雨季时应限速行车。

用增稳系数评价钾肥配合秸秆还田对作物的增产稳定性效应

根据长期定位试验结果,提出增产稳定性系数(增稳系数)指标,据此研究化学钾肥和秸秆配合施用对小麦玉米产量的持续增产稳定性效应,以期更合理评价钾肥配合秸秆还田这一施肥方式对作物增产稳定性的影响。试验共设4个处理,分别为:(1)只施氮磷肥的对照(NP);(2)在对照基础上加施秸秆(NPSt);(3)在对照基础上加施钾肥(NPK);(4)在对照基础上加施秸秆和钾肥(NPKSt)。结果表明:增稳系数可以作为评价施肥方案对作物产量长期持续增产效应的综合指标;不同施肥方案的长期持续增产效应定量分析表明,钾肥配合秸秆还田方案不但促进作物增产,还能提高增产的持续稳定性。

降压增注技术在低渗透油田的应用研究

针对吴旗长2油藏部分注水井注入压力高、注水驱替效率低及套损井不断增加等情况,分析了注水压力升高的原因,开展了新型表面活性剂体系降压增注的应用研究。该体系由单一两性表面活性剂和黏土稳定剂组成。室内实验表明,60℃该体系与吴旗长2油样间的界面张力可达到10-2～10-3 mN.m-1数量级,且具有较好的界面张力稳定性。岩心驱油降压模拟试验表明,驱替5～10 PV新型活性剂体系后,岩心水驱降压率达到30%以上,驱油效率的提高值也在7%以上。在吴旗区块吴72-71井进行了单井现场试验,该井见到了活性剂体系较好的降压增注效果。

有机无机配施对土壤养分环境及小麦增产稳定性的影响

针对太行山山前平原生态类型区土壤有机质含量和土壤氮储量偏低，增产潜力下降和稳定性差等问题，在河北省辛集市马兰农场进行小麦培肥定位试验，研究化肥和有机肥配施对土壤有机质和NPK养分的影响。结果表明，化肥配合有机肥施用对土壤养分环境的培肥作用，优于化肥配合等养分含量的秸秆直接还田。相对不施肥的对照，不同肥力地块土壤有机质、全氮、碱解氮、全磷、有效磷、速效钾分别增加14．59％～19．2％、5．7％-14．81％、10．38％-24．30％、8．63％～10．89％、93．19％～107．24％、17．69％-55．18％，小麦产量增加75．64％～79．7％，增稳系数增加3．03—3．19。在太行山山前平原区，一般施用量在化肥N210kg·hm^-2，P2O5 90kg·hm^-2，K2O 90kg·hm^-2，有机肥折合养分含量在N65k·hm^-2，P2O5 18kg·hm^-2，K2O5 6kg·hm^-2，有机C量1500—3000kg·hm^-2，可达到稳定增进土壤氮磷钾养分环境，改善土壤有机质状况，稳定增加小麦产量的积极培肥作用。

冬小麦高产栽培新途径的研究

在分析以往高产典型及山东小麦高产途径演变的基础上,提出一条稳住叶面积系数、控制株型增穗数的小麦高产栽培新途径。并对运用该途径实现单产超过9 t/hm2的麦田进行分析,该途径通过先控后促的肥水运筹和通过减少单株叶面积增加单位面积成穗数等措施建立起大密度-小株型的群体结构,该结构在提高收获指数和粒叶比方面有明显的优势,且有助于促进源库流在高水平上协调与平衡,从而可实现产量上的突破。同时还为小麦高产育种和高产栽培研究提供了参考。

基于重度增加法的边坡稳定性三维有限元分析

提出了分析边坡稳定性的三维非线性有限元重度增加法。利用ANSYS软件,基于D-P准则,考虑了关联的流动法则,先保持土体强度指标粘聚力和内摩擦角不变,通过逐步增加重度的方法使土体达到临界状态,采用坡顶水平位移与重度增加系数关系曲线上位移陡然增大作为边坡的破坏标准。充分考虑了土体的空间作用机制和变形协调机制,通过计算得到可能的半球形或复合形滑动面的位置和形式,而不是事先去假定,得到的安全系数也与其他方法相近。该方法可以更好地模拟土坡的破坏,有助于了解土坡的破坏机理,其结果对工程实践具有指导作用。