Minimum safe thickness of rock plug in karst tunnel according to upper bound theorem

High pressure and water-bearing caverns ahead of a karst tunnel face tend to cause geological disasters, such as water and mud bursts. So, the determination of safe thickness of the reserved rock plug is a key technical problem to be solved for karst tunnel construction. Based on the Hoek-Brown nonlinear failure criterion, the minimum safe thickness of rock plug was investigated in the light of the limit analysis theory. On the basis of the proposed failure mode, the expression of the minimum thickness for rock plug was obtained by means of upper bound theorem in combination with variational principle. The calculation results show the influence of each parameter on safe thickness and reveal the damage range of rock plug. The proposed method is verified by comparing the results with those of the drain cavern of Maluqing Tunnel. The research shows that with the increase of compressive strength and tensile strength as well as constant A of Hoek-Brown criterion, the safe thickness decreases, whereas with the increase of cavern pressure, tunnel diameter, and constant B from Hoek-Brown criterion, the safe thickness increases. Besides, the tensile strength, or constants A and B affect the shear failure angle of rock plug structure, but other parameters do not. In conclusion, the proposed method can predict the minimum safe thickness of rock plug, and is useful for water burst study and prevention measures of tunnels constructed in high-risk karst regions.

Effect of Stagnation Temperature on the Supersonic Two-Dimensional Plug Nozzle Conception. Application for Air

When the stagnation temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this temperature. The gas remains perfect, its state equation remains always valid, except it will name in more calorically imperfect gas or gas at High Temperature. The goal of this research is to trace the profiles of the supersonic plug nozzle when this stagnation temperature is taken into account, lower than the threshold of dissociation of the molecules, by using the new formula of the Prandtl Meyer function, and to have for each exit Mach number, several nozzles shapes by changing the value of this temperature. A study on the error given by the PG （perfect gas） model compared to our model at high temperature is presented. The comparison is made with the case of a calorically perfect gas aiming to give a limit of application of this model. The application is for the air.

Production of Rubidium Bose-Einstein Condensate in an Optically Plugged Magnetic Quadrupole Trap

We experimentally produce the rubidium Bose-Einstein condensate in an optically plugged magnetic quadrupole trap. A far blue-detuned focused laser beam with a wavelength of 532nm is plugged in the center of the magnetic quadrupole trap to increase the number of trapped atoms and to suppress the heating. An rf evaporative cooling in the magneto-optical hybrid trap is applied to decrease the atom temperature into degeneracy. The atom number of the condensate is 1.2（0.4）× 10^5 and the temperature is below lOOnK. We also study characteristic behaviors of the condensate, such as phase space density, condensate fraction and anisotropic expansion.

Influence of Incomplete Soil Plugs on Bearing Capacities of Bucket Foundations in Clay

Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be evaluated.In this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil plug.Then,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are analyzed.The results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ratio.However,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure mode.The contact ratio hardly affects the horizontal bearing capacity of bucket foundations.Moreover,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than 0.5.Consequently,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil plugs.The comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.

Curing kinetics and plugging mechanism of high strength curable resin plugging material

Lost circulation, a recurring peril during drilling operations, entails substantial loss of drilling fluid and dire consequences upon its infiltration into the formation. As drilling depth escalates, the formation temperature and pressure intensify, imposing exacting demands on plug materials. In this study, a kind of controllable curing resin with dense cross-network structure was prepared by the method of solution stepwise ring-opening polymerization. The resin plugging material investigated in this study is a continuous phase material that offers effortless injection, robust filling capabilities, exceptional retention, and underground curing or crosslinking with high strength. Its versatility is not constrained by fracture-cavity lose channels, making it suitable for fulfilling the essential needs of various fracture-cavity combinations when plugging fracture-cavity carbonate rocks. Notably, the curing duration can be fine-tuned within the span of 3-7 h, catering to the plugging of drilling fluid losing of diverse fracture dimensions. Experimental scrutiny encompassed the rheological properties and curing behavior of the resin plugging system, unraveling the intricacies of the curing process and establishing a cogent kinetic model. The experimental results show that the urea-formaldehyde resin plugging material has a tight chain or network structure. When the concentration of the urea-formaldehyde resin plugging system solution remains below 30%, the viscosity clocks in at a meager 10 mPa·s. Optimum curing transpires at 60℃, showcasing impressive resilience to saline conditions. Remarkably, when immersed in a composite saltwater environment containing 50000 mg/L NaCl and 100000 mg/L CaCl_(2), the urea-formaldehyde resin consolidates into an even more compact network structure, culminating in an outstanding compressive strength of 41.5 MPa. Through resolving the correlation between conversion and the apparent activation energy of the non-isothermal DSC curing reaction parameters, the study attests to the fulfillment of the kinetic equation for the urea-formaldehyde resin plugging system. This discerning analysis illuminates the nuanced shifts in the microscopic reaction mechanism of the urea-formaldehyde resin plugging system. Furthermore, the pressure bearing plugging capacity of the resin plugging system for fractures of different sizes is also studied. It is found that the resin plugging system can effectively resident in parallel and wedge-shaped fractures of different sizes, and form high-strength consolidation under certain temperature conditions. The maximum plugging pressure of resin plugging system for parallel fractures with outlet size 3 mm can reach 9.92 MPa, and the maximum plugging pressure for wedge-shaped fractures with outlet size 5 mm can reach 9.90 MPa. Consequently, the exploration and application of urea-formaldehyde resin plugging material precipitate a paradigm shift, proffering novel concepts and methodologies in resolving the practical quandaries afflicting drilling fluid plugging.

A novel responsive stabilizing Janus nanosilica as a nanoplugging agent in water-based drilling fluids for exploiting hostile shale environments

Thermo-responsive nanocomposites have recently emerged as potential nanoplugging agents for shale stabilization in high-temperature water-based drilling fluids(WBDFs). However, their inhibitory properties have not been very effective in high-temperature drilling operations. Thermo-responsive Janus nanocomposites are expected to strongly interact with clay particles from the inward hemisphere of nanomaterials, which drive the establishment of a tighter hydrophobic membrane over the shale surface at the outward hemisphere under geothermal conditions for shale stabilization. This work combines the synergistic benefits of thermo-responsive and zwitterionic nanomaterials to synchronously enhance the chemical inhibitions and plugging performances in shale under harsh conditions. A novel thermoresponsive Janus nanosilica(TRJS) exhibiting zwitterionic character was synthesized, characterized,and assessed as shale stabilizer for WBDFs at high temperatures. Compared to pristine nanosilica(Si NP)and symmetrical thermo-responsive nanosilica(TRS), TRJS exhibited anti-polyelectrolyte behaviour, in which electrolyte ions screened the electrostatic attraction between the charged particles, potentially stabilizing nanomaterial in hostile shaly environments(i.e., up to saturated brine or API brine). Macroscopically, TRJS exhibited higher chemical inhibition than Si NP and TRS in brine, prompting a better capability to control pressure penetration. TRJS adsorbed onto the clay surface via chemisorption and hydrogen bonding, and the interactions became substantial in brine, according to the results of electrophoretic mobility, surface wettability, and X-ray diffraction. Thus, contributing to the firm trapping of TRJS into the nanopore structure of the shale, triggering the formation of a tight hydrophobic membrane over the shale surface from the outward hemisphere. The addition of TRJS into WBDF had no deleterious effect on fluid properties after hot-treatment at 190℃, implying that TRJS could find potential use as a shale stabilizer in WBDFs in hostile environments.

Fracture propagation law of temporary plugging and diversion fracturing in shale reservoirs under completion experiments of horizontal well with multi-cluster sand jetting perforation

This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation.The effects of temporary plugging agent(TPA)particle size,TPA concentration,single-cluster perforation number and cluster number on plugging pressure,multi-fracture diversion pattern and distribution of TPAs were investigated.A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures.The addition of fibers can quickly achieve ultra-high pressure,but it may lead to longitudinal fractures extending along the wellbore.The temporary plugging peak pressure increases with an increase in the concentration of the TPA,reaching a peak at a certain concentration,and further increases do not significantly improve the temporary plugging peak pressure.The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number.A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure,and it has a more significant control on the propagation of multi-cluster fractures.A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures,while a higher number of clusters makes it difficult to achieve effective plugging.The TPAs within the fracture is mainly concentrated in the complex fracture areas,especially at the intersections of fractures.Meanwhile,the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures.

Transportation and sealing pattern of the temporary plugging ball at the spiral perforation in the horizontal well section

Multistage fracturing of horizontal wells is a critical technology for unconventional oil and gas reservoir stimulation. Ball-throwing temporary plugging fracturing is a new method for realizing uniform fracturing along horizontal wells and plays an important role in increasing oil and gas production. However,the transportation and sealing law of temporary plugging balls(TPBs) in the perforation section of horizontal wells is still unclear. Using COMSOL computational fluid dynamics and a particle tracking module, we simulate the transportation process of TPBs in a horizontal wellbore and analyse the effects of the ball density, ball diameter, ball number, fracturing fluid injection rate, and viscosity on the plugging efficiency of TPB transportation. This study reveals that when the density of TPBs is close to that of the fracturing fluid and a moderate diameter of the TPB is used, the plugging efficiency can be substantially enhanced. The plugging efficiency is greater when the TPB number is close to twice the number of perforations and is lower when the number of TPBs is three times the number of perforations.Adjusting the fracturing fluid injection rate from low to high can control the position of the TPBs,improving plugging efficiency. As the viscosity of the fracturing fluid increases, the plugging efficiency of the perforations decreases near the borehole heel and increases near the borehole toe. In contrast, the plugging efficiency of the central perforation is almost unaffected by the fracturing fluid viscosity. This study can serve as a valuable reference for establishing the parameters for temporary plugging and fracturing.

High-strain dynamic model of large-diameter pipe piles with soil plug for vertical vibration analysis

A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter openended pipe piles(OEPPs)and surrounding soil undergoing high-strain impact loading.To describe the soil behavior,the soil along pile shaft is divided into slip and nonslip zones and the base soil is modeled as a fictitious-soil pile(FSP)to account for the wave propagation in the soil.True soil properties are adopted and slippage at the pile-soil interface is considered,allowing realistic representation of largediameter OEPP mechanics.The developed model is validated by comparing with conventional models and finite element method(FEM).It is further used to successfully simulate and interpret the behaviors of a steel OEPP during the offshore field test.It is found that the variation in the vertical vibrations of shaft soil along radial direction is significant for large-diameter OEPPs,and the velocity amplitudes of the internal and external soil attenuate following different patterns.The shaft soil motion may not attenuate with depth due to the soil slippage,while the wave attenuation at base soil indicates an influence depth,with a faster attenuation rate than that in the pile.The findings from the current study should aid in simulating the vibration behaviors of large-diameter OEPP-soil system under high-strain dynamic loading.

Dynamic plugging regulating strategy of pipeline robot based on reinforcement learning

Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the pipeline and PIPR. In this paper, we propose a dynamic regulating strategy to reduce the plugging-induced vibration by regulating the spoiler angle and plugging velocity. Firstly, the dynamic plugging simulation and experiment are performed to study the flow field changes during dynamic plugging. And the pressure difference is proposed to evaluate the degree of flow field vibration. Secondly, the mathematical models of pressure difference with plugging states and spoiler angles are established based on the extreme learning machine (ELM) optimized by improved sparrow search algorithm (ISSA). Finally, a modified Q-learning algorithm based on simulated annealing is applied to determine the optimal strategy for the spoiler angle and plugging velocity in real time. The results show that the proposed method can reduce the plugging-induced vibration by 19.9% and 32.7% on average, compared with single-regulating methods. This study can effectively ensure the stability of the plugging process.

A Gel-Based Solidification Technology for Large Fracture Plugging

Fault fractures usually have large openings and considerable extension. Accordingly, cross-linked gel materials aregenerally considered more suitable plugging agents than water-based gels because the latter often undergo contaminationvia formation water, which prevents them from being effective over long times. Hence, in this study, aset of oil-based composite gels based on waste grease and epoxy resin has been developed. These materials havebeen observed to possess high compressive strength and resistance to the aforementioned contamination, therebyleading to notable increase in plugging success rate. The compressive strength, thickening time, and resistance toformation water pollution of these gels have been evaluated indoors. The results show that the compressivestrength of the gel can reach 11 MPa;additionally, the related gelation time can be controlled to be more than3 h, thereby providing a safe construction time;Invasion of formation water has a small effect on the gel strengthand does not shorten the thickening time. All considered performance indicators of the oil-based gel confirm itssuitability as a plugging agent for fault fractures.

Study on Chrome-free Purging Plugs for Steel Ladles

Purging plug refractories in China typically contain around 3 mass% of super-fine chromium oxide in the matrix in order to improve the performance of the purging plugs, primarily, slag corrosion and wear resistance. Alternatives to chromium oxide containing refractories have gained interest due to health concerns related to the formation of soluble chromium compounds over long storage periods of refractory wastes. Super-ground reactive alumina can replace chromium oxide in purging plug refractories and this paper discussed the new reactive alumina E-SY 88 in comparison to chromium oxide in a typical purging plug castable. The mixing behaviour, wet castable properties, as well as cured, dried, and fired properties at different temperatures up to 1 600 ℃ were compared. In addition, the hot modulus of rupture, creep behaviour, thermal shock resistance and slag corrosion resistance were tested. The microstructure after slag corrosion was investigated by SEM. The results prove that E-SY 88 is an economically viable technical alternative to chromium oxide in purging plug refractories.

Plugging Up the loopholes

State regulator tightens supervision over state overseas assets NEW measures to supervise overseas assets of centrally administered state-owned enterprises(SOEs) have been announced by the State-Owned Assets Supervision and Administration Commission(SASAC), coming about amid what it termed "increasing complexities." The newly announced pair of regula-

Feasibility of Plug Production Utilizing Digestate from Home-Waste to Energy Systems (H-WEF)

The integration of sustainable technologies in waste management systems has become imperative in addressing the escalating challenges of agricultural productivity and sustainability. Plugs are essential when starting crop production in controlled environment agriculture (CEA) setups and greenhouses. Horticultural crops such as vegetables, fruiting, and ornamental plants that utilize plugs have demonstrated higher success rates, healthier plants, and higher total yields. The APS Laboratory for Sustainable Agriculture explored the innovative utilization of digestate from the Home Water-Energy-Food Systems (H-WEF). The H-WEF system converts household food waste into biogas, electricity, and nutrient-rich digestate. The digestate from the H-WEF system was used to produce agricultural plugs, presenting a novel approach to circular resource utilization. We carried out the growth of Rex Butterhead Lettuce Latuca sativa plugs with 1) control system (synthetic fertilizer) and seven different treatments, 2) 5% Digestate—95% RO Water (5D–95RO);3) 10% Digestate—90% RO Water (10D–90RO);4) 15% Digestate—85% RO Water (15D–85RO);5) 20% Digestate—80% RO Water (20D–80RO);6) 25% Digestate—75% RO Water (25D–75RO);7) 30% Digestate—70% RO Water (30D–70RO);8) 35% Digestate—65% RO Water (35D–65RO). The plugs were cultivated for 15 days in a controlled environment until two leaves had developed after the cotyledon. After 15 days, we collected data on wet weight (g), plug head area (cm2), total leaf area (cm2), total chlorophyll content (mg/cm2), and dry weight (g). In addition, we collected data on the Leaf Area Index (LAI, cm2/cm2) and Specific Leaf Area (SLA, cm2/g). The synthetic fertigation yielded a higher wet weight than the following treatments: 5D–95RO, 10D–90RO, and 35D–65RO. While the 30D–70RO treatment produced a larger plug head than all other treatments. The digestate-based fertilizers were comparable to the synthetic fertilizer at dilutions of 25D–75RO and 30D–70RO. This study underscores the viability of using digestate for plug production, providing crucial insights for growers navigating the challenges of sustainable agricultural practices.

Plug-in混合动力汽车能量管理策略全局优化研究

应用动态规划全局优化算法,针对并联式Plug-in混合动力汽车在不同行驶里程下的能量管理策略进行了全局优化研究。结果表明:车辆的行驶里程小于55km时应使用电动机为主的能量管理策略,当车辆的行驶里程大于55km时应使用发动机为主的能量管理策略;在动态规划最优控制下,车辆行驶里程为55km时整车经济性能最佳,行驶里程小于110km时整车平均等价油耗为2.7L/100km,相对于原型车经济性提高了近58%。

Smart Plug泪小管塞治疗水液缺乏型干眼症临床初步观察

目的:探讨Smart Plug泪小管塞治疗水液缺乏型干眼症临床疗效。方法:选取2012-05/2013-04期间我院收治的48例水液缺乏型干眼症患者为研究对象,进行Smart Plug泪小管塞治疗,观察术后临床疗效、基础泪液分泌试验(SchirmerⅠtest,SⅠt)、泪膜破裂时间(tear break up time,BUT)、角膜荧光素染色(fluoreseein staining,FL)变化。结果:本组48例患者,显效31例(65%),有效14例(29%),无效3例(6%),总有效率为94%。治疗前,患者SⅠt,BUT,FL分别为3.49±1.24mm/5min,3.15±1.07s,2.52±0.11分。治疗后,患者SⅠt,BUT,FL均明显改善,与治疗前比较,差异具有统计学意义(P<0.05)。1例患者术后有异物感,8h后栓子脱落;1例患者于术后8mo出现肉芽组织,泪小管塞脱落。其余病例无下泪小管感染或肉芽肿。结论:Smart Plug泪小管塞治疗水液缺乏型干眼症疗效确切,能够有效缓解临床症状,值得临床推广。

PLUG引物和IT引物在顶芒山羊草分子标记建立中的通用性分析

分子标记是检测和追踪小麦背景中近缘物种染色体的重要手段。依据禾本科物种基因共线性原则,基于基因序列设计的引物在不同物种中可能具有通用性。本研究对水稻PLUG引物和簇毛麦IT引物在顶芒山羊草中的通用性进行了分析,并建立了顶芒山羊草染色体特异IT标记。供试的397对PLUG引物和841对IT引物对小麦-顶芒山羊草双二倍体与中国春的扩增结果显示,377对(95.0%)PLUG引物和593对(70.5%)IT引物可以在供试材料中扩增出清晰条带。因此,PLUG引物在顶芒山羊草中的通用性优于IT引物。相比小麦对照,PLUG引物和IT引物能在小麦-顶芒山羊草双二倍体中扩增出多态性条带的引物数分别有17对和5对,分别占供试PLUG引物和IT引物的4.3%和0.6%。利用获得的IT多态性引物对一套小麦-顶芒山羊草附加系和一套小麦-卵穗山羊草附加系进行扩增,结果发现仅引物CINAU1060、CINAU1465和CINAU1517能在相应附加系中扩增出大小分别约为300、480bp和320bp的多态性标记,为小麦背景中顶芒山羊草染色质的鉴定提供了新的检测手段。然而,本研究中IT引物建立顶芒山羊草分子标记的比率仅为0.4%,低于我们之前用PLUG引物建立顶芒山羊草分子标记的比率(8.9%)。

Visiplug~泪小管塞栓治疗中度以上干眼的临床疗效分析

目的探讨应用眼表综合分析仪评估Visi Plug泪小管塞栓治疗中度以上干眼的临床疗效。方法选择2015年1月至2016年3月于我院诊断为干眼并使用人工泪液及普拉洛芬滴眼液4周后仍有症状并再次评分为中度以上干眼的患者32例(64眼),分成治疗组和对照组,每组各16例32眼,治疗组使用泪小管塞栓联合人工泪液及普拉洛芬滴眼液进行治疗,对照组继续使用人工泪液和普拉洛芬滴眼液治疗,随访6~12个月,分别观察治疗前及治疗后2周、1个月、3个月、6个月、末次随访时干眼主观症状问卷调查得分、眼表综合分析仪中泪膜破裂时间、泪河高度、眼红指数及角膜荧光素染色检查情况并评估临床疗效。结果治疗后1 a,主观症状问卷调查评分治疗组由术前(16.95±5.12)分降至(4.36±0.16)分,对照组由术前(17.22±5.20)分降至(5.50±0.29)分,两组治疗前差异无统计学意义(P>0.05),治疗后1 a差异有统计学意义(P<0.01)。治疗组、对照组治疗前与治疗后不同时间点的泪膜破裂时间、泪河高度、眼红指数、角膜荧光素染色评分的差异均有统计学意义(均为P<0.05)。两组在治疗后泪膜破裂时间均较治疗前显著延长、泪河高度均较治疗前显著增加,眼红指数评分和角膜荧光素染色评分均较治疗前显著降低,差异均有统计学意义(均为P<0.05),但治疗组与对照组相比,泪膜破裂时间更长,泪河高度改善更为明显,眼红指数评分与角膜荧光素染色评分更低。结论 Visi Plug泪小管塞栓治疗中度以上干眼具有良好的临床效果。应用眼表综合分析仪评估Visi Plug~泪小管塞栓治疗中度以上干眼的临床疗效更加客观、简便。

模糊神经网络算法Plug in电动车能量管理控制器

针对Plug in混合动力汽车研究设计基于模糊神经网络算法的整车能量管理控制器。将驾驶行为用神经网络进行建模,驾驶模式、踏板(油门和刹车)位置以及当前车轮力矩作为神经网络输入,目标力矩作为输出;并将道路类型、目标力矩、电池SOC、当前车轮力矩为模糊输入变量,以满足整车动力性能、燃油经济型和极限边界极值为约束条件,对混合动力汽车的能量进行分配与管理,用advsior软件进行了仿真,基于该算法在DSP硬件平台设计实现能量管理控制器,通过算法仿真和样车测试表明:在行驶里程60 km等价燃油经济型最好,随着行驶里程增加燃油经济型下降,整个测试过程中样车动力性能以及各部件工况良好。

Plug封堵器新方法在细小动脉导管未闭治疗中的应用

目的探讨Plug封堵器新方法在细小动脉导管未闭介入治疗中的临床疗效。方法选择细小动脉导管未闭的患者38例,全部常规采取经肺动脉侧释放法,可以建立轨道的患者20例为对照组,如果经肺动脉侧不能建立轨道,则采用冠脉技术,经主动脉侧释放法的患者18例为试验组,于术后造影以及术后3天、1个月、3个月、6个月行超声心动图随访,观察研究两组封堵成功率、并发症和远期疗效。结果两组技术成功率100%,试验组的X线辐射剂量为(140.0±5.4)mGy,手术总时间为(20.0±2.6)min,对照组的X线辐射剂量为(200.0±6.2)mGy,手术总时间为(30.0±3.1)min,术后3天、1个月、3个月、6个月超声心动图随访均无残余分流,封堵器位置好,肺动脉压力正常。结论 Plug封堵器新方法介入治疗细小动脉导管未闭安全可行,试验组的X线辐射剂量及手术总时间均较对照组少,试验组优于对照组。