Hydromechanical characterization of gas transport amidst uncertainty for underground nuclear explosion detection

Given the challenge of definitively discriminating between chemical and nuclear explosions using seismic methods alone,surface detection of signature noble gas radioisotopes is considered a positive identification of underground nuclear explosions(UNEs).However,the migration of signature radionuclide gases between the nuclear cavity and surface is not well understood because complex processes are involved,including the generation of complex fracture networks,reactivation of natural fractures and faults,and thermo-hydro-mechanical-chemical(THMC)coupling of radionuclide gas transport in the subsurface.In this study,we provide an experimental investigation of hydro-mechanical(HM)coupling among gas flow,stress states,rock deformation,and rock damage using a unique multi-physics triaxial direct shear rock testing system.The testing system also features redundant gas pressure and flow rate measurements,well suited for parameter uncertainty quantification.Using porous tuff and tight granite samples that are relevant to historic UNE tests,we measured the Biot effective stress coefficient,rock matrix gas permeability,and fracture gas permeability at a range of pore pressure and stress conditions.The Biot effective stress coefficient varies from 0.69 to 1 for the tuff,whose porosity averages 35.3%±0.7%,while this coefficient varies from 0.51 to 0.78 for the tight granite(porosity<1%,perhaps an underestimate).Matrix gas permeability is strongly correlated to effective stress for the granite,but not for the porous tuff.Our experiments reveal the following key engineering implications on transport of radionuclide gases post a UNE event:(1)The porous tuff shows apparent fracture dilation or compression upon stress changes,which does not necessarily change the gas permeability;(2)The granite fracture permeability shows strong stress sensitivity and is positively related to shear displacement;and(3)Hydromechanical coupling among stress states,rock damage,and gas flow appears to be stronger in tight granite than in porous tuff.

A Numerical Method on Inverse Determination of Heat Transfer Coefficient Based on Thermographic Temperature Measurement

The heat transfer coefficient in a multidimensional heat conduction problem is obtained from the solution of the inverse heat conduction problem based on the thermographic temperature measurement. The modified one-dimensional correction method （MODCM）, along with the finite volume method, is employed for both two- and three-dimensional inverse problems. A series of numerical experiments are conducted in order to verify the effectiveness of the method. In addition, the effect of the temperature measurement error, the ending criterion of the iteration, etc. on the result of the inverse problem is investigated. It is proved that the method is a simple, stable and accurate one that can solve successfully the inverse heat conduction problem.

Parallel Physics-Informed Neural Networks Method with Regularization Strategies for the Forward-Inverse Problems of the Variable Coefficient Modified KdV Equation

This paper mainly introduces the parallel physics-informed neural networks(PPINNs)method with regularization strategies to solve the data-driven forward-inverse problems of the variable coefficient modified Korteweg-de Vries(VC-MKdV)equation.For the forward problem of the VC-MKdV equation,the authors use the traditional PINN method to obtain satisfactory data-driven soliton solutions and provide a detailed analysis of the impact of network width and depth on solving accuracy and speed.Furthermore,the author finds that the traditional PINN method outperforms the one with locally adaptive activation functions in solving the data-driven forward problems of the VC-MKdV equation.As for the data-driven inverse problem of the VC-MKdV equation,the author introduces a parallel neural networks to separately train the solution function and coefficient function,successfully addressing the function discovery problem of the VC-MKdV equation.To further enhance the network’s generalization ability and noise robustness,the author incorporates two regularization strategies into the PPINNs.An amount of numerical experimental data in this paper demonstrates that the PPINNs method can effectively address the function discovery problem of the VC-MKdV equation,and the inclusion of appropriate regularization strategies in the PPINNs can improves its performance.

Calculation of Activity Coefficient from Immiscible Binary Alloy Phase Diagram by Means of Modified Sub-regular Solution Model

The modified sub regular solution model was used for a calculation of the activity coefficient of immiscible binary alloy systems. The parameters needed for the calculation are the interaction parameters, λ 1 and λ 2, which are represented as a linear function of temperature, T . The molar excess Gibbs free energy, G m E, can be written in the form G m E= x A x B[( λ 11 + λ 12 T )+( λ 21 + λ 22 T ) x B ] The calculation is carried out numerically for three immiscible binary alloy systems, Al Pb, Cu Tl and In V. The agreement between the calculated and experimentally determined values of activity coefficient is excellent.

Amending Research on the Expression of the Contact Force of the Spindle Barrel Finishing Based on EDEM Simulation

The spindle barrel finishing is commonly used to improve the surface integrity of the important parts of the high-end equipment while it is difficult to provide enough test artifacts for the traditional trial and error experiment to obtain the desirable processing technology.The EDEM simulation of the spindle barrel finishing can provide effective help for the process design,however,the difference between the simulation and experiment is closely related to the selection of the contact model during simulation.In this paper,simulations and experiments are conducted based on the identical apparatus and conditions to facilitate the comparison and validation between each other.Based on the Hertz contact theory,the effect of the material properties of contact objects and the relative position of the workpiece on the contact force is qualified.The expression of the correlation coefficient of the contact model is deduced.Then the formula for calculating the contact force between the barrel finishing abrasive and the workpiece that includes influence coefficient of the material properties and the relative positions is established.Finally,the contact force calculation formula is verified by changing the rotating speed.The result shows that the material correction coefficient ranges from 1.41 to 2.38,which is inversely related to the equivalent modulus E.The position correction coefficient ranges from 2.0 to 2.3.The relative error value between the calculation result and the experimental test result is from 0.58%to 14.07%.This research lay a theoretical foundation for the correction theory of the core elements of the spindle barrel finishing process.

A Modified Certainty Coefficient Method(M-CF) for Debris Flow Susceptibility Assessment:A Case Study for the Wenchuan Earthquake Meizoseismal Areas

In the meizoseismal areas hit by the China Wenchuan earthquake on May 12, 2008, the disasterprone environment has changed dramatically, making the susceptibility assessment of debris flow more complex and uncertain. After the earthquake, debris flow hazards occurred frequently and effective susceptibility assessment of debris flow has become extremely important. Shenxi gully in Du Jiangyan city, located in the meizoseismal areas, was selected as the study area. Based on the research of disaster-prone environment and the main factors controlling debris flow, the susceptibility zonations of debris flow were mapped using factor weight method(FW), certainty coefficient method(CF) and geomorphic information entropy method(GI). Through comparative analysis, the study showed that these three methods underestimated susceptible degree of debris flow when used in the meizoseismal areas of Wenchuan earthquake. In order to solve this problem, this paper developed a modified certainty coefficient method(M-CF) to reflect the impact of rich loose materials on the susceptible degree of debris flow. In the modified method, the distribution and area of loose materials were obtained by field investigations and postearthquake remote sensing image, and four data sets, namely, lithology, elevation, slop and aspect, wereused to calculate the CF values. The result of M-CF method is in agreement with field investigations and the accuracy of the method is satisfied. The method has a wide application to the susceptibility assessment of debris flow in the earthquake stricken areas.

Research on Partial Coefficients for Design of Quarter-circular Caisson Breakwater

The quarter-circular caisson breakwater （QCB） is a new type of breakwater, and it can be applied in deepwater. The stability of QCB under wave force action can be enhanced, and the rubble mound engineering can be less than that of semi-circular breakwaters in deepwater. In order to study the wave force distribution acting on the QCB, to find wave force formula for this type of breakwater, firstly in this paper, the distribution characteristics of the horizontal force, the downward vertical force and the uplift force on the breakwater were gotten based on physical model wave flume experiments and on the analysis of the wave pressure experimental data. Based on a series of physical model tests acted by irregular waves, a kind of calculation method, which was modified by Goda formula, was proposed to carry out the wave force on the QCB. Secondly, the reliability method with correlated variables was adopted to analyze the QCB, considering the high correlation between wave forces or moments. Utilizing the observed wave data in engineering field, the reliability index and failure probability of QCB were obtained. Finally, a factor Q=0.9 is given to modify the zero pressure height above SWL of QCB, and wave force partial coefficient 1.34 to the design expressions of QCB for anti-sliding, as well as 1.67 for anti-overturning, were presented.

ON DIAGNOSTIC ANALYSIS OF ENERGY FIELDS OF EXPLOSIVE ENHANCEMENT OF TYPHOON OFFSHORE

The energetics process of offehore typhoon in three kinds of explosive enhancement (TEE) are ana lyzed using ECMWF data. The results are as follows: (a) During the explosive development process，the enhancement of the rotational kinetic enersy (K) is mainly in the lower troposphere while that ofthe potential energy (PE) is in the upper troposphere. The magnitude of rotational kinetic energy islargely bigger than that of divergent enersy (KX). (b) The environmental energy advected into the typhoon was about 30% of the internal increment of typhoon energy. The magnitude of energy was an order larger than increment of typhoon energy. (c) Among those three kinds of explosively developed typhoon, the enersy transformation mechanisms are different. (d) The influence of environment fields onabrupt intensification of typhoons couldn’t be overestimated.

Service Life Design for Concrete Engineering in Marine Environments of Northern China Based on a Modified Theoretical Model of Chloride Diffusion and Large Datasets of Ocean Parameters

In this study,through experimental research and an investigation on large datasets of the durability parameters in ocean engineering,the values,ranges,and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were confirmed.Based on a modified theoretical model of chloride diffusion and the reliability theory,the service lives of concrete structures exposed to the splash,tidal,and underwater zones were calculated.Mixed concrete proportions meeting the requirement of a service life of 100 or 120 years were designed,and a cover thickness requirement was proposed.In addition,the effects of the different time-varying relationships of the boundary condition(Cs)and diffusion coefficient(Df)on the service life were compared;the results showed that the time-varying relationships used in this study(i.e.,Cscontinuously increased and then remained stable,and Dfcontinuously decreased and then remained stable)were beneficial for the durability design of concrete structures in marine environment.

Implementation of a Petrographical and Petrophysical Workflow Protocol for Studying the Impact of Heterogeneity on the Rock Typing and Reservoir Quality of Reefal Limestone:A Case Study on the Nullipore Carbonates in the Gulf of Suez

This study focuses on the heterogeneity of the middle Miocene syn-rift Belayim nullipore(reefal)marine sequences in the Gulf of Suez and its impacts on reservoir quality.The sequences consist of coralline algal reef limestones with a highly complex dual-porosity system of primary and secondary porosities of widely varying percentages.To achieve a precise mathematical modeling of these reservoir sequences,a workflow protocol was applied to separate these sequences into a number of hydraulic flow units(HFUs)and reservoir rock types(RRTs).This has been achieved by conducting a conventional core analysis on the nullipore marine sequence.To illustrate the heterogeneity of the nullipore reservoir,the Dykstra-Parsons coefficient(V)has been estimated(V=0.91),indicating an extremely heterogeneous reservoir.A slight to high anisotropy(λ_(k))has been assigned for the studied nullipore sequences.A stratigraphic modified Lorenz plot(SMLP)was applied to define the optimum number of HFUs and barriers/baffles in each of the studied wells.Integrating the permeability-porosity,reservoir quality index-normalized porosity index(RQI-NPI)and the RQI-flow zone indicator(RQIFZI)plots,the discrete rock types(DRT)and the R35 techniques enable the discrimination of the reservoir sequences into 4 RRTs/HFUs.The RRT4 packstone samples are characterized by the best reservoir properties(moderate permeability anisotropy,with a good-to-fair reservoir quality index),whereas the RRT1 mudstone samples have the lowest flow and storage capacities,as well as the tightest reservoir quality.

Effect of Pneumatic Boxing Gloves on Impact Kinematics and Their Relationship to Impact Forces

This study was aimed at improved understanding of the mechanisms of previously reported protective effects of a pneumatic boxing glove. A Motion Capture System was used to obtain velocity data from four different boxing gloves dropped on to a force plate from nine heights ranging from 1 to 5 metres. Two gloves were of the conventional type but differed in mass. The other two were prototype pneumatic gloves. One of these (SBLI) had a sealed bladder while the other (ARLI) incorporated a port allowing air exchange with the external environment. The pneumatic gloves decelerated more slowly than the conventional gloves following impact and compressed through a greater absolute distance. Consequently, they took longer to reach zero velocity. As drop height increased, these trends became more pronounced for the ARLI glove than the SBLI glove. Increase in velocity during rebound was also slower for the pneumatic gloves. The ARLI glove had a lower coefficient of restitution than any of the other gloves at low to moderate drop heights but not at high drop heights. The SBLI glove had a higher coefficient of restitution than the other gloves at all drop heights from 2 metres upwards. This indicated that, overall, the ARLI glove was the most effective, and the SBLI glove the least effective, in dissipating the kinetic energy of impact through conversion to other energy forms. For all gloves at all drop heights, peak positive acceleration at the beginning of rebound was of lower absolute magnitude than peak negative acceleration at the end of compression. The influence of drop height on an index characterising this relationship differed between the conventional and pneumatic gloves, possibly reflecting structural changes to gloves as impact energy increased. The conventional and pneumatic gloves differed regarding temporal alignment between key kinematic and kinetic events, and there were some differences between the two pneumatic gloves in this respect. Nevertheless, peak glove deceleration correlated highly with peak impact force, not only for each glove individually but also when data for all gloves were combined. The findings confirmed the potential practical utility of the ARLI glove and identified air cushion thickness, glove compressibility and capacity for air release and subsequent reuptake as critical aspects of its design.

基于旋转黏度的SBS改性沥青黏温特性及流体行为分析

采用3种基质沥青制备相应的SBS改性沥青,测试了不同温度和剪切速率下的黏度。根据Andrada方程计算了6种沥青的黏流活化能(E_(a));根据幂律方程,分别计算了6种沥青的非牛顿指数(ζ)和稠度系数(μ),分析了改性沥青的流体特性以及黏度对剪切速率的依赖性。结果表明,Andrada方程能够较好地描述沥青及改性沥青的黏温关系,E_(a)能够反映黏度对温度的敏感性,SBS改性可以显著提升沥青的黏度,但不同改性沥青的温度敏感性存在差异。SBS改性沥青的ζ值均小于1,沥青由牛顿流体向非牛顿流体转化,不同类型沥青之间非牛顿性的相对强弱随温度的变化呈现出复杂性,稠度系数(μ)随温度的升高而减小。

露天矿山大孔径预裂爆破参数研究与应用

预裂爆破是控制边坡成形、降低爆破动载影响的重要手段。为研究炮孔直径203 mm预裂爆破最佳不耦合系数和炮孔间距,运用LS-DYNA数值软件建立以不耦合系数、炮孔间距为变量的数值模型,分析不同工况下炮孔周围的裂纹扩展和峰值应力强度。结果表明:在空气不耦合系数分别为2.53、2.90、3.38、4.06、5.07、6.77的6种工况中,不耦合系数为4.06时,爆炸能量的利用率最高、裂纹扩展良好,与理论公式推导相符;进一步建立空气不耦合系数为4.06,炮孔间距为1.5、2.0、2.5、3.0、3.5 m的5组模型,得到炮孔间距为2.5 m时满足孔间裂纹贯穿条件,符合现场工况要求;现场应用效果较好,为类似工程提供借鉴。

刚性挡土墙后轻量土静止土压力特性模型试验研究

为了研究轻量土对挡土结构物的减压机理,通过开展大比尺刚性挡土墙模型试验,采用重物堆载的方式在填土表面施加均布荷载,分析重塑黄土和轻量土作为墙后填土时的静止土压力分布规律。结果表明:轻量土在养护阶段的静止土压力随着时间增长而逐渐增大,但增幅逐渐降低。重塑黄土和轻量土的静止土压力随着填土深度增加近似线性增大,并且静止土压力随着加载而逐渐增大,其中重塑黄土的增幅明显偏大。对比重塑黄土和轻量土的静止土压力,发现轻量土具有明显的减压作用,且填土表面均布荷载越大,轻量土的减压效果越好。重塑黄土和轻量土的静止土压力系数均不是常数,其中重塑黄土静止土压力系数为0.34~0.78,轻量土静止土压力系数为0.22~0.55。当填土表面作用均布荷载时,传统理论在计算重塑黄土静止土压力方面适用性较高,但轻量土计算误差较大。结合模型试验以及传统理论,提出了适用于轻量土的静止土压力修正公式,对比发现其相对误差总体上介于1.01%~23.13%。通过模型试验和理论计算揭示了轻量土的静止土压力特性,对于完善轻量土土压力理论具有重要意义。

改性煤矸石-海藻酸钠粉体对管道内甲烷/空气爆炸的抑爆实验

以工业固废煤矸石(coal gangue,CG)为原料,通过焙烧、酸碱激发和物理研磨等方法对其进行改性,得到一种表面粗糙、比表面积较大的微孔改性煤矸石(modified coal gangue,MCG)材料。以MCG作为基体,采用机械化学技术(mechanochemical technology,MCT)将一种新型阻燃剂海藻酸钠(sodium alginate,SA)与MCG进行复配,制备出一种高效、环保、经济的改性煤矸石-海藻酸钠(MCG-SA)粉体抑爆剂。运用热重分析仪、扫描电子显微镜、X射线衍射分别对上述3种粉体进行表征,以确定其热分解特性、微观形貌和晶相成分。在自行搭建实验平台的基础上探究了MCG、SA及MCG-SA复合粉体在不同复配比、不同添加质量条件下对甲烷-空气预混气体的爆炸压力、火焰传播速度等特性参数的影响。研究结果表明:MCG、SA及MCG-SA复合粉体具有良好的抑爆效果,且复合粉体的抑爆能力优于单一粉体。其中,质量为250 mg、SA质量分数为50%的复合粉末对甲烷体积分数为9.5%的甲烷-空气爆炸的协同抑制效果最显著,最大爆炸压力和最大火焰传播速度分别降低36.72%和68.93%,最大爆炸压力和最大火焰传播速度的抵达时间分别延长243.36%和171.33%。

不耦合装药下岩石爆破块体尺寸的分布特征

通过不同装药结构下立方体红砂岩小型爆破实验,分析了岩石的损伤程度和破坏模式,同时引入三参数极值分布函数量化岩石爆破块体尺寸分布特征。此外,根据岩样R1的爆破实验结果进行了有限元数值模型验证,基于验证的模型展开了岩石单孔爆破损伤破裂行为的模拟,讨论了径向、轴向不耦合系数和耦合介质对岩石破碎效果的影响。结果表明,三参数极值分布函数可以较好地表征岩石爆破后破碎块体尺寸分布特征,块体平均尺寸随着不耦合系数的减小呈线性降低趋势,且破碎块度趋于均匀。通过比较不同耦合介质装药时岩石内部的能量分布特征和破坏体积发现,水作为耦合介质时,爆炸能量的传递效率最高,其次分别是湿砂和干砂,空气的能量传递效率最低。结合等效波阻法计算的理论应力透射系数可以很好地反映不耦合装药时岩石的破碎程度。

一种新爆轰产物状态方程及其在炸药爆轰性能预测上的应用

为准确描述爆轰产物在高温高压下的热力学关系,拓展应用范围,实现CHNO单质/混合炸药与含能金属盐爆轰性能的可靠预测,基于Exp⁃6势的维里系数理论值建立了新气态爆轰产物状态方程Virial⁃Peng⁃Long(VPL),并基于更准确的“冷压”项与考虑金属高压热运动变化的“晶格振动”项建立了新凝聚态金属产物三项式状态方程Wu⁃Chen⁃Peng(WCP)。应用VPL计算了几种典型CHNO单质/混合炸药的爆轰参数,应用VPL与WCP评价了几种典型含能金属盐的爆轰CJ参数与驱动做功能力。结果表明,相比VLW和BKW,基于VPL能够更准确评价CHNO单质/混合炸药的爆轰性能,对太安(PETN)爆速预测偏差在±2.1%以内,最高不超过2.5%;对RHT⁃901驱动圆筒稳定速度预测误差绝对值<1%。而VPL与WCP能够准确预测含能金属盐爆轰性能,其中对叠氮化铅爆轰CJ参数计算相对误差不超过±4%;对铜叠氮化物驱动飞片速度预测相对误差绝对值小于1%。

基于气泡统一方程的水下爆炸气泡迁移特征参数影响规律研究

气泡统一方程能够高效描述考虑多种因素的球状气泡动力学行为,但描述气泡迁移方程中的特征参数对于气泡行为的影响规律以及如何确定特征参数尚不明晰.基于气泡统一方程建立了理论模型进行计算与“欧拉有限元”数值算法以及经典球状气泡理论模型进行对比,并结合以下爆炸实验,进一步验证了气泡统一方程的科学性以及相较于其他理论模型的优势.在此基础上,探究了迁移方程特征参数对自由场水下爆炸气泡动力学的影响规律.研究表明,拖曳力系数和附加质量系数对于气泡第一周期脉动的影响可忽略不计,拖曳力系数相比于附加质量系数对气泡迁移的影响更具有主导作用.当拖曳力系数较大时,其对气泡迁移产生明显的阻碍效果,反之不足以对气泡迁移提供阻碍效果.附加质量系数对气泡迁移也是阻碍作用,其对气泡迁移的影响近乎线性.确定迁移特征参数需要围绕具体问题来分析,基于研究结果并结合相似实验可以明确迁移特征参数,并采用理论计算为水下爆炸实际工程应用提供指导与参考.

Theory and test of underground explosions:Coupling rule between cratering and ground shock

Calculating the parameters of the ground shock induced by an underground explosion is a complex energy coupling problem.It is difficult to establish a unified ground shock coupling law from limited test data.This paper summarizes the research results obtained at home and abroad and systematically analyzes the coupling mechanism of craters formed by an underground explosion and the ground shock.The differences between the concepts of"closed-explosion critical depth"and"equivalent closed-explosion critical depth"are clearly explained.The spreading of the ground shock energy is attributed to the explosive expansion of the air cavity,revealing a linear relationship between the volume of the cavity region(or the volume of the crack region)and the ground shock energy associated with the underground explosion.The proportionality factor is related to the mechanical properties of the medium and is independent of the magnitude of the explosion equivalent.Based on this,a theoretical calculation formula and conversion method for the ground shock coupling coefficient were established.Explosion tests were conducted in clay and Plexiglass under varying burial depths.The test results were consistent with the theoretically calculated results.Our study provides a theoretical basis for the design of explosion-resistant structures in underground engineering.

复杂地物背景角域后向散射分布特性研究

针对采用平均后向散射系数进行对地空炸毫米波引信回波仿真时,因照射区域内入射角度散布较大造成仿真精度不足的问题,对复杂地物背景后向散射特性测试的远场条件进行了讨论,修正了复杂地物背景毫米波近场测试远场条件表达式,提出一种针对引信对地探测的复杂地物背景角域后向散射分布建模方法,构建基于实测数据优化的土耕地、水泥地等背景角域后向散射场,分析其对引信探测响应回波的影响。仿真结果表明,接近垂直入射情况下与传统乌拉比模型比较一致性较好,接近水平入射情况下比乌拉比模型后向散射系数小2~4 dB。利用该引信回波算法提高了毫米波引信探测仿真精度,可为对地空炸毫米波引信探测器设计提供数据支撑。