Experimental and numerical investigation of groundwater head losses on and nearby short intersections between disc-shaped fractures          下载免费PDF全文

Ci-xiao Qu  Ming-yu Wang  Peng Wang 《地下水科学与工程》2022,10(1):33-43

Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computational treatments.The flow velocity has a large spatial differentiation which is more likely to produce non-linear flow and additional head losses on and nearby intersections in such shaped fractures,therefore it is necessary to understand and quantify them.In this study,both laboratory experiments and numerical simulations were performed to investigate the total head loss on and nearby the intersections as well as the local head loss exactly on the intersections,which were not usually paid sufficient attention or even ignored.The investigation results show that these two losses account for 29.17%-84.97%and 0-73.57%of the entire total head loss in a fracture,respectively.As a result,they should be necessarily considered for groundwater modeling in fractured rocks.Furthermore,both head losses become larger when aperture and flow rate increase and intersection length decreases.Particularly,the ratios of these two head losses to the entire total head loss in a fracture could be well statistically explained by power regression equations with variables of aperture,intersection length,and flow rates,both of which achieved high coefficients of determination.It could be feasible through this type of study to provide a way on how to adjust the groundwater head from those obtained by numerical simulations based on the traditional linear flow model.Finally,it is practicable and effective to implement the investigation approach combining laboratory experiments with numerical simulations for quantifying the head losses on and nearby the intersections between disc-shaped fractures.  相似文献   

含水采空区全空间瞬变电磁响应分析     

陈健强  李雁川  田浩  李汉超 《物探与化探》2021,(2):546-550

针对含水采空区全空间瞬变电磁响应信号识别问题,采用有限元数值模拟及现场实测方法,基于电动势—视电阻率及对应时深转换关系,获取了全扇面视电阻率随深度变化的空间分布规律,提取了低阻异常区测点感应电动势衰减曲线,得出了测点随探测角度变化的电动势量化变化规律。基于上述研究,开展了井下钻探验证及钻孔窥视,并对现场钻孔出水水样进行了水质分析。结果表明:含水采空区的瞬变电磁响应横向角度对应一致性高于纵向深度;其感应电动势升幅与感应电动势差值变化趋势相反,呈现出在二次场观测初期急剧增大而后趋缓的特征,最大升幅可达10倍以上。钻探工程及化探分析进一步验证了物探成果。  相似文献   

煤岩体孔隙结构应力特征的数值模拟研究     

王刚  江成浩  陈雪畅 《煤田地质与勘探》2021,49(1):57-64,80

为了探究不同加载方式下煤岩体孔隙周围的应力分布规律,通过CT三维重建技术构建含有不同孔隙形状的煤岩体骨架模型,并利用ABAQUS软件进行单轴、三轴压缩实验模拟。结果表明,球状孔隙结构在单轴压缩条件下,上下区域表现为拉应力集中,左右区域表现为压应力集中。不同倾角的椭球状孔隙结构其长短轴区域的应力集中类型不同。单轴压缩过程中,轴向加载速度影响球状孔隙周围的Mises应力峰值和σ₁应力的变化;三轴压缩过程中,孔隙结构依然经历了压密、弹性、塑性和破坏4个阶段,较低的围压条件使得弹性阶段“应力-应变”曲线与“应力-时间”曲线高度重合。从微观角度为煤岩体力学研究提供了一种新的方法和思路。   相似文献   

基于水热耦合的青藏高原分布式水文模型——Ⅱ.考虑冰川和冻土的尼洋河流域水循环过程模拟          下载免费PDF全文

刘扬李  周祖昊  刘佳嘉  王鹏翔  李玉庆  朱熠明  姜欣彤  王康  王富强 《水科学进展》2021,32(2):201-210

尼洋河流域是雅鲁藏布江第四大支流,受冰川、积雪和冻土影响,水循环关系极其复杂。为深入研究该区域内的水文循环过程,本文在寒区水循环模型（WEP-COR）的基础上,针对青藏高原气候和地质特点,构建了耦合“积雪-土壤-砂砾石层”连续体和“积雪-冰川”水热过程模拟的青藏高原分布式水循环模型（WEP-QTP）。在尼洋河流域通过对2013—2016年的流量过程模拟发现,工布江达和泥曲站的逐月流量Nash-Sutcliffe效率系数分别达到0.810和0.752,比改进前的0.430和0.095有明显提升;以2015年为例,对比WEP-COR和WEP-QTP模型发现,WEP-QTP模型在汛期特别是主汛前（冻土融化期）模拟的流量过程不会出现较大的波动,模拟得到的逐日流量Nash-Sutcliffe效率系数相比WEP-COR从-0.67提高到0.54。模型增强了地下水含水层的调节作用,使得流量过程更加平稳且接近实测,研究结果表明,WEP-QTP模型适用于青藏高原的水文模拟。  相似文献   

高温硬岩空气潜孔锤钻头设计          下载免费PDF全文

罗宏保  李俊萍  吴金生 《探矿工程》2021,48(4):60-65

干热岩试验性开发井钻井施工,在高温硬岩的地层条件下,如何实现高效钻进仍存在很多技术难点。空气潜孔锤钻进技术是解决硬岩地层钻进的有效方法之一,潜孔锤钻头是空气潜孔锤钻进的关键器具。根据青海共和干热岩GH-01井空气潜孔锤钻进技术应用情况,分析探讨了空气潜孔锤钻头断齿、掉齿、磨损严重、使用寿命短等问题,从钻头结构设计、钻头材料选取、钻头冷压固齿工艺等几个方面对空气潜孔锤钻头进行了优化。固齿优化过程中采用有限元分析方法,对钻头冷压固齿过盈量进行仿真分析计算,根据分析计算结果确定最优固齿过盈量。通过对潜孔锤钻头结构、材料、加工等优化,为适用于高温硬岩的空气潜孔锤钻头研制提供了借鉴。为提高空气潜孔锤钻进综合效率,为干热岩钻探开发提供了技术支持和技术储备。  相似文献   

同轴双向回转钻进破岩效率研究          下载免费PDF全文

曹彦伟  李谦 《探矿工程》2021,48(S1):70-78

国内外相关研究均显示同轴双向回转可有效降低钻具振动和提高破岩效率,但双向回转相对传统单向回转的钻进效率的提升水平研究较少。据此,本文建立双向回转钻头以及单向回转钻头与岩石相互作用的有限元模型,以破岩比功作为评价指标量化比较分析了2种钻头的破岩效率。通过定义双向钻头内外壁尺寸差、内外钻头的间隙、内钻头壁厚与双向钻头内外壁尺寸差之比、内外钻头转速比和内外钻头底部高度差5种核心参数,并设计正交试验完成了仿真分析。结果显示,内外钻头高度差与内外钻头间隙对于破岩比功影响比较小,内外钻头尺寸差、内外钻头转速比和内钻头壁厚与双向钻头内外尺寸差之比对破岩比功影响显著。  相似文献   

祁连山区多年冻土空间分布模拟   总被引：1，自引：1，他引：0  

彭晨阳  盛煜  吴吉春  曹伟  何彬彬 《冰川冻土》2021,43(1):158-169

祁连山区位于青藏高原东北边缘,是亚洲水塔重要的组成部分,多年冻土的变化对生态系统和水资源平衡有着重要影响。基于青藏高原第二次综合科学考察、道路勘察钻孔点以及前人所获得的多年冻土下界资料,回归得出祁连山区多年冻土下界统计模型,借助ArcGIS平台在DEM数据的支持下,模拟出祁连山区多年冻土空间分布图。结果表明：祁连山区多年冻土分布的下界具有良好的地带性规律,表现为随经纬度增加而降低的规律;祁连山区多年冻土在空间分布上呈现出以哈拉湖为中心向四周扩散的分布格局;祁连山区总面积约为16.90×10⁴ km²,其中多年冻土面积约为8.03×10⁴ km²,占总面积约47.51%。多年冻土区与季节冻土区之间存在着有不连续多年冻土分布的过渡区,过渡区面积约1.43×10⁴ km²,占总面积约8.46%。  相似文献   

Extenuating the parameters using HEC-HMS hydrological model for ungauged catchment in the central Omo-Gibe Basin of Ethiopia          下载免费PDF全文

Demisse Habtamu Semunigus  Ayalew Abebe Temesgen  Ayana Melkamu Teshome  Lohani Tarun Kumar 《地下水科学与工程》2021,9(4):317-325

Characteristics of ungauged catchments can be studied from the hydrological model parameters of gauged catchments. In this research, discharge prediction was carried out in ungauged catchments using HEC-HMS in the central Omo-Gibe basin. Linear regression, spatial proximity, area ratio, and sub-basin mean were amalgamated for regionalization. The regional model parameters of the gauged catchment and physical characteristics of ungauged catchments were collated together to develop the equations to predict discharge from ungauged catchments. From the sensitivity analysis, crop coefficient (CC), storage coefficient (R), constant rate (CR), and time of concentration (TC) are found to be more sensitive than others. The model efficiency was evaluated using Nash–Sutcliffe Efficiency (N_SE) which was greater than 0.75, varying between ?10% and +10% and the coefficient of determination (R²) was approximated to be 0.8 during the calibration and validation period. The model parameters in ungauged catchments were determined using the regional model (linear regression), sub-basin mean, area ratio, and spatial proximity methods, and the discharge was simulated using the HEC-HMS model. Linear regression was used in the prediction where p-value ≤ 0.1, determination coefficient (R²) = 0.91 for crop coefficient (CC) and 0.99 for maximum deficit (MD). Constant rate (CR), maximum storage (MS), initial storage (IS), storage coefficient (R), and time of concentration (TC) were obtained. The result is that an average of 30 m³/s and 15 m³/s as the maximum monthly simulated flow for ungauged sub-catchments, i.e. Denchiya and Mansa of the main river basin .  相似文献   

免共振沉桩过程对地表振动影响的FLAC3D数值模拟     

魏家斌  王卫东  吴江斌 《吉林大学学报(地球科学版)》2021,51(5):1514-1522

为研究免共振沉桩过程对地表振动影响,采用密度放大法以消除模型桩弹性模量过大对计算效率的影响,在有限差分软件FLAC^3D中建立了相应的连续振动沉桩模型,并和文献中的现场测试结果进行了比较,分析了激振力幅值和振动频率这两个施工参数对地表振动响应的影响。结果表明：密度放大法可有效提高数值模拟的计算效率,模拟沉桩7.0倍桩径（4.9 m）所需计算时间约为12.0 h,数值结果较好地模拟了现场测试中免共振沉桩的地表振动影响;激振力幅值和振动频率均主要对近场（水平距离为5.0倍桩径范围内）的地表振动有明显影响;临界沉桩深度与地表振动影响峰值相对应,该深度随水平距离先增大后趋于稳定;激振力幅值对临界沉桩深度的改变不明显,振动频率对远场临界沉桩深度则有较明显影响。  相似文献   

边界层参数化对海南岛海风环流结构模拟的影响   总被引：2，自引：0，他引：2  

杨秋彦  苗峻峰  王语卉 《热带气象学报》2019,35(2):234-252

利用WRF V3.7详细分析了应用8种边界层参数化方案（YSU、MYNN2.5、MYNN3、ACM2、BouLac、UW、SH、GBM）所模拟的2014年5月25日海南岛海风环流结构的差异,其中YSU、ACM2和SH为非局地闭合方案,MYNN2.5、MYNN3、BouLac、UW和GBM为局地闭合方案。结果表明:对于海风环流水平结构的模拟,15时,YSU、ACM2、BouLac、UW和SH模拟的北部海风较强,SH和GBM的内陆风速偏大。温度与海风发展强度相对应,MYNN2.5与MYNN3模拟的岛屿温度偏低,海陆温差小,海风相对较弱。对于海风环流垂直结构的模拟,09时海风开始,但强度较小,且存在残余陆风,向内陆传播距离较短,YSU、MYNN2.5和SH方案的海风相对较强。12时,海风已呈现出较为清晰的环流结构,YSU和ACM2的海风厚度及向内陆传播距离相对强于其它方案,MYNN3的环流结构则不太明显,且向内陆推进距离短,海风相对较弱。15时,海风发展强盛,MYNN2.5和MYNN3方案模拟的海风垂直强度较小,ACM2方案的海风垂直环流特征最为明显。18时,海风的强度和扰动均有所减弱,ACM2、BouLac和UW的整体海风相对强于其它方案。21时海风已基本转为陆风,BouLac与UW的陆风环流结构最为清晰。位温、水汽及海风垂直环流强度的发展变化与海风的演变过程基本一致。造成ACM2模拟海风偏强的原因是其边界层垂直混合偏强,形成了足够的湍流混合强度所致。对于边界层高度的模拟,ACM2的边界层顶最高,这与此方案所模拟的海风强度偏大相吻合,其它方案的边界层高度与海风强度并不完全一致。   相似文献