An analytical model for estimating rock strength parameters from small-scale drilling data

The small-scale drilling technique can be a fast and reliable method to estimate rock strength parameters. It needs to link the operational drilling parameters and strength properties of rock. The parameters such as bit geometry, bit movement, contact frictions and crushed zone affect the estimated parameters.An analytical model considering operational drilling data and effective parameters can be used for these purposes. In this research, an analytical model was developed based on limit equilibrium of forces in a Tshaped drag bit considering the effective parameters such as bit geometry, crushed zone and contact frictions in drilling process. Based on the model, a method was used to estimate rock strength parameters such as cohesion, internal friction angle and uniaxial compressive strength of different rock types from operational drilling data. Some drilling tests were conducted by a portable and powerful drilling machine which was developed for this work. The obtained results for strength properties of different rock types from the drilling experiments based on the proposed model are in good agreement with the results of standard tests. Experimental results show that the contact friction between the cutting face and rock is close to that between bit end wearing face and rock due to the same bit material. In this case,the strength parameters, especially internal friction angle and cohesion, are estimated only by using a blunt bit drilling data and the bit bluntness does not affect the estimated results.

A study of the load transfer behavior of fully grouted rock bolts with analytical modelling

Fully grouted rock bolts have been used in mining industry for many years.Much research has been conducted to evaluate the load transfer behavior of fully grouted rock bolts with experimental programs.However,compared with that,less work has been conducted with analytical modelling.Therefore,in this paper,the authors used an analytical model to study the load transfer behavior of fully grouted rock bolts.To confirm the credibility of this analytical model,an in-situ pull-out test was used to validate this model.There was a close match between the experimental result and the analytical result.Following it,a parametric study was conducted with this analytical model.The influence of coefficients,Young’s modulus of the rock bolt and the diameter of the rock bolt on the load transfer performance of rock bolts was studied.Furthermore,the load distribution along the fully grouted rock bolt was analytically studied.The results show that the axial load in the rock bolt decayed from the loaded end to the free end independent of the pull-out load.However,the trend of the load distribution curve was influenced by the pull-out load.This paper was beneficial for better understanding the load transfer mechanism of fully grouted rock bolts.

Three-Dimensional Analytical Modeling of Axial-Flux Permanent Magnet Drivers

In this paper, the axial-flux permanent magnet driver is modeledand analyzed in a simple and novel way under three-dimensional cylindricalcoordinates. The inherent three-dimensional characteristics of the deviceare comprehensively considered, and the governing equations are solved bysimplifying the boundary conditions. The axial magnetization of the sectorshapedpermanent magnets is accurately described in an algebraic form bythe parameters, which makes the physical meaning more explicit than thepurely mathematical expression in general series forms. The parameters of theBessel function are determined simply and the magnetic field distribution ofpermanent magnets and the air-gap is solved. Furthermore, the field solutionsare completely analytical, which provides convenience and satisfactoryaccuracy for modeling a series of electromagnetic performance parameters,such as the axial electromagnetic force density, axial electromagnetic force,and electromagnetic torque. The correctness and accuracy of the analyticalmodels are fully verified by three-dimensional finite element simulations and a15 kW prototype and the results of calculations, simulations, and experimentsunder three methods are highly consistent. The influence of several designparameters on magnetic field distribution and performance is studied and discussed.The results indicate that the modeling method proposed in this papercan calculate the magnetic field distribution and performance accurately andrapidly, which affords an important reference for the design and optimizationof axial-flux permanent magnet drivers.

A Sensitivity Study on Parameterization Scheme of Snow Internal and Interfacial Processes in Snow Model

In order to develop a seasonal snow model of land surface process as accurately as possible for climatic study. it is necessary to fully understand the effects of important snow internal processes and interaction with air and to get an insight into influence of several relevant parameterization schemes with parameters' uncertainty to some degree. Using the snow model (SAST) developed by first author and other one and some useful field observation data, this paper has conducted a series of sensitivity studies on the parameterization schemes. They are relative to compaction process, snow thermal conduction, methodology of layering snow pack and to key parameters such as snow albedo, water holding capacity. Then, based on the results from the sensitivity studies, some useful conclusions for snow cover model improvement are obtained from the analysis of the results.

A Novel Interconnect Crosstalk Parallel RLC Analyzable Model Based on the 65nm CMOS Process

Based on the 65nm CMOS process,a novel parallel RLC coupling interconnect analytical model is presented synthetically considering parasitical capacitive and parasitical inductive effects. Applying function approximation and model order-reduction to the model, we derive a closed-form and time-domain waveform for the far-end crosstalk of a victim line under ramp input transition. For various interconnect coupling sizes, the proposed RLC coupling analytical model enables the estimation of the crosstalk voltage within 2.50% error compared with Hspice simulation in a 65nm CMOS process. This model can be used in computer-aided-design of nanometer SOCs.

Determination of the constant m_(i) in the Hoek-Brown criterion of rock based on drilling parameters

The constant m_(i) in the Hoek-Brown(H-B) criterion is a fundamental parameter required for determining the compressive strength of rock. In this paper, drilling parameters provide a new basis for determining the constant mi. An analytical relationship between the drilling parameters and constant miis established in consideration of the contact response between the drilling bit and the cut rock in the crushed zone.New models are developed to predict the triaxial compressive strength(TCS), internal friction angle φand cohesion c of rock. Drilling tests are carried out on 6 rock types to study the correlation between φ and m_(i). A comparison between the predicted values of rock mechanical properties and the measured values from the laboratory is performed to verify the accuracy of the proposed model(yielding an error less than 10%). The TCSs and constant m_(i) values of fifteen rocks are cited to validate the accuracy of the proposed model. The result shows that the proposed model predicts the TCS and constant m_(i) within a maximum error of 20%. The method can be conveniently applied to the rock mechanical properties.

THEORETICAL ANALYSIS AND PRACTICE ON THE SELECTION OF KEY PARAMETERS FOR HORIZONTAL BIAS BURNER

The air flow ratio and the pulverized coal mass flux ratio between the rich and lean sides are the key parameters of horizontal bias burner. In order to realize high combustion efficiency, excellent stability of ignition, low NO x emission and safe operation, six principal demands are presented on the selection of key parameters. An analytical model is established on the basis of the demands, the fundamentals of combustion and the operation results. An improved horizontal bias burner is also presented and applied. The experiment and numerical simulation results show the improved horizontal bias burner can realize proper key parameters, lower NO x emission, high combustion efficiency and excellent performance of part load operation without oil support. It also can reduce the circumfluence and low velocity zone existing at the downstream sections of vanes, and avoid the burnout of the lean primary air nozzle and the jam in the lean primary air channel. The operation and test results verify the reasonableness and feasibility of the analytical model.

A Simplified Formulation to Estimate Influence of Gearbox Parameters on the Rattle Noise

Occurrence of gear rattle in transmission systems can result in severe vibration and noise,which in applications such as automobiles is an important source of user discomfort.As a result,the reduction of the rattling noise has attracted lot of concerns.The rattling noise level is affected by several gearbox parameters,an understanding of which is essential to prevent the expensive design modifications at later stages of product development.To develop such understanding at the gearbox design stage,this paper analytically evaluates the gear parameters’effect on the root mean square of the wheel gear acceleration under idling condition,which is known to be linearly correlated to the rattling noise level.Therefore,this evaluation allows for an investigation of the gear parameters’influence on the rattling noise as well.This method is then verified by comparing the analytical results with the simulation results from a dynamic model built in SIMPACK as well as previously published experimental results.Thus,the proposed analytical evaluation method can optimize the gearbox specifications at the design stage to reduce the gear rattle noise level.

发电机定子环形励磁绕组寄生电容解析模型与容值降低方法

励磁控制器是调节发电机励磁电流,控制发电机电压的核心部件。采用宽禁带功率器件(例如碳化硅、氮化镓器件)的励磁控制器具有损耗低、开关频率高的优点,而电路中的寄生电容会影响功率管的开关性能,增加开关损耗,带来震荡和电磁干扰问题等。励磁绕组寄生电容是励磁控制电路的重要组成部分,降低其容值可有效提升控制器性能。为了探寻有效的容值降低方法,建立考虑匝间距离、匝到铁心距离和层间距离的多层绕组寄生电容解析模型;通过田口法计算参数灵敏度得到影响寄生电容的关键参数,研究寄生电容的变化规律;在考虑槽空间约束情况下得到降低多层定子环形励磁绕组寄生电容的有效方法;通过实验验证解析模型的准确性和降低寄生电容方法的有效性。

大尺度离散裂缝的渗透率应力敏感研究——以顺北油田为例

为解决大尺度离散裂缝渗透率应力敏感模型针对性不强的问题,文中基于裂缝介质内秉渗透率和离散裂缝充填长方体支撑物模型,建立了大尺度离散裂缝的内秉渗透率-应力解析模型,分析了裂缝渗透率与孔隙压力、裂缝渗流物理/力学参数的关系。研究表明:当裂缝面孔隙度大于0.8时,渗透率损失程度随着孔隙度的增加快速增加,导致大尺度离散裂缝和小尺度连续裂缝渗透率应力敏感的差异;同时,弹性模量平均每下降1000 MPa,渗透率应力敏感指数增加19.26%,而泊松比对应力敏感指数的影响并不显著。文中建立的内秉渗透率应力敏感模型在顺北油田生产动态数值模拟研究中取得了较好的应用效果。

变温条件下解析Preisach磁滞模型误差修正和特征参数辨识方法

温度升高会影响磁性材料的磁滞特性,从而改变电气设备的性能。目前解析Preisach模型无法对温度进行有效表征,导致损耗计算结果误差较大。为此,本文首先分析了基于Lorentzian函数的解析Preisach模型特征参数对磁滞回线形状参数的影响程度,如饱和磁通密度、矫顽力、剩磁等,研究了不同温度下模型参数和材料磁特性的变化。根据模型特征参数具有的磁滞回线形状相关性和温度相关性,引进温度系数来修正模型特征参数,构建变温条件下的解析Preisach模型,并给出了计及温度影响的模型参数辨识方法。最终实验测量纳米晶合金在变温条件下的极限磁滞回线,对多组实测值和修正后的解析Preisach模型计算值进行对比后,得出在饱和磁通密度、矫顽力和剩磁处修正模型结果的平均相对误差分别为0.15%、2.21%、5.76%,证明了该修正模型的准确性。

工艺参数对不锈钢管切割表面质量的影响研究

不锈钢管切割质量主要受到切口断面毛刺的影响,对不锈钢管切割时毛刺的形成过程及工艺参数对切口质量的影响规律进行分析。首先,建立解析模型描述切口毛刺的产生过程,分析切口毛刺形成的影响因素;其次,运用有限元仿真软件,建立奥氏体不锈钢316L材料的三维切削仿真模型,模拟切削加工过程,分析切削完成后切口毛刺的形貌特征;最后,针对切口毛刺形成的影响因素,对切削过程进行单因素仿真。对减少切口毛刺的形成和优化工艺参数提供理论指导。

屈服摇摆消能双层框架墩结构横桥向地震反应分析

为控制双层框架墩结构地震损伤,提升结构震后功能恢复能力,本文提出一种屈服消能摇摆双层框架墩结构,结合拉格朗日方程和动量矩定理建立了结构横桥向地震反应分析模型。针对典型双层桥梁框架墩结构分别建立了现浇分析模型、自由摇摆分析模型和屈服消能摇摆分析模型,并采用远场地震动、近场无脉冲地震动和近场脉冲地震动对结构进行横桥向地震反应分析和结构参数影响规律分析。分析结果表明,摇摆桥墩可避免桥墩发生残余变形,且防屈曲阻尼器的设置起到了较好的减隔震及抗倒塌作用,尤其是在近场脉冲地震动作用下效果最为显著;摇摆结构参数对结构地震反应有明显影响,下层结构地震反应随着摇摆桥墩高宽比、尺寸参数和下层梁墩质量比的增大呈减小趋势,而上层现浇结构地震反应呈相反趋势,值得注意的是较小的上层结构固有频率将会增加现浇墩柱发生塑性变形的可能性。

基于改进黑猩猩算法的解析Preisach模型参数辨识

解析Preisach模型解决了Preisach模型因离散Everett函数造成的测量误差大、数值不稳定的问题,但是解析Preisach模型同时存在参数多、辨识复杂的问题。针对上述问题,提出一种融合多策略的改进黑猩猩优化算法,来实现对解析Preisach模型的参数快速、精确辨识。首先,引入自适应权重因子来平衡全局搜索和局部开发能力;其次,将差分变异策略应用到种群个体位置更新中,增强算法个体间的信息交流,扩大搜索范围;最后,使用柯西变异和高斯变异相结合的随机扰动策略,进一步增强算法跳出局部最优的能力。结合实验数据,分别使用遗传算法、黑猩猩算法、正弦余弦黑猩猩算法与所提算法对解析Preisach模型参数进行辨识,并基于辨识结果对取向硅钢片的磁滞回线进行模拟。通过磁滞回线拟合度、适应度值变化以及损耗误差分析3个方面的结果对比可得,所提算法在解析Preisach模型的参数辨识上兼具辨识精度高、收敛速度快的优点。

An improved creep model for unsaturated reticulated red clay

Establishment of a creep model is an important method to analyze the relationship between soil creep deformation and time,and the element model is widely used for studying soil creep.However,the element creep model is employed for fitting saturated soil,and the mechanical element model is generally linear,which cannot well fit the nonlinear deformation of the soil with time in practice.The creep process of the soil is not only time-dependent,but also related to the deviatoric stress level.Therefore,the fractional calculus theory and a parameter n reflecting the effect of deviatoric stress level on the creep properties of the soil were introduced into the element model,and the fractional qBurgers creep model was established by using the fractional Koeller dashpot and Caputo fractional calculus.The proposed model was used to fit the triaxial test data of reticulated red clay under different net confining pressures and matric suctions by unsaturated triaxial apparatus.The proposed model can well describe the nonlinearity of unsaturated reticulated red clay,has memory and global correlation to the creep development process of unsaturated reticulated red clay,and has clear physical meaning.The functional relationships of the model parameters with the matric suction,net confining pressure and deviatoric stress level were deduced,so that the creep curves of unsaturated reticulated red clay can be obtained for any conditions,which is of great value for the study of unsaturated soils.

基于物理模型试验的隧道涌水量预测参数优化研究

隧道涌水量的预测对施工安全、进度和人员的保护非常重要,为提高解析法预测隧道涌水量的精度,本文基于模型试验,构建了隧道两侧具有稳定补给水源的模型,探讨隧道排水造成的水位降深与渗透系数及水头的关系,推导水位降深折减公式,并基于工程案例验证水位降深折减公式的合理性。结果表明:水位降深折减公式提高了解析法预测涌水量的精度,可适用于相似条件下的隧道涌水量预测。

大变形锚杆支护效应分析

根据大变形锚杆的力学和变形特性,建立大变形锚杆–围岩相互作用结构模型,研究锚杆加固圆形隧道时的支护效应,并通过数值模拟验证了模型和求解方法的有效性。采用上述求解方法,定量分析了原岩应力、岩体强度以及大变形锚杆安装密度、长度和安装时间对其支护效果的影响规律。结果表明,在高应力或极软岩等恶劣地质条件下,围岩产生较大位移的情况下,大变形锚杆可以更好的发挥支护效应。大变形锚杆加固的主要作用在于限制塑性区围岩的变形,对塑性区边界的位置以及弹性区岩体变形的控制效果不明显。还通过改变安装锚杆时等效内支撑力的大小,揭示了锚杆安装时间对其支护效应的影响规律。研究结果可为大变形锚杆支护设计及参数优化提供基础理论依据。

流滑型崩岸河岸侧蚀模式初探

流滑型崩岸是冲积河流河岸常见的一种崩塌形式,其发展速度快、破坏力强;该类崩岸主要取决于水流的直接冲刷,河岸崩退过程中水面与岸顶高差较小。依据此类崩岸的特征,基于水流冲刷分析,在基础层面上初步探讨并建立了流滑型崩岸的河岸侧蚀模式。结合水槽试验与土工离心模拟试验,对该模式进行了分析研究,初步率定了模式中的河岸侧蚀系数,计算值与实测值吻合较好。该模式参数少、应用方便,可为流滑型崩岸中河岸侧蚀的估算及河道横向变形数值模拟提供参考依据。

基于现场锤击试验的地铁轨道振动特性分析及参数研究

近来，由于轮轨共振而产生的地铁钢轨异常波磨问题备受关注。轨道结构动力特性分析是开展轮轨耦合振动研究的基础，地铁轨道结构的动力特性取决于各组成部分（钢轨、扣件、轨枕和道床等）的物理特性及其组合形式。基于轨道结构的周期性频域解析模型，结合北京地铁在线锤击试验，通过计算轨道结构在脉冲荷栽下的频响函数，对0～2000Hz频段内轨道结构的动力响应主频进行分析；并通过改变轨道结构参数，分别研究了不同轨道结构参数对各轨道结构动力响应主频的影响情况。研究结果表明：轨下支撑刚度对钢轨共振频率影响较大，枕下支撑刚度对轨道系统共振频率影响较大，轨下和枕下支撑阻尼仅能改变各共振频率点的响应幅值；轨枕支撑间距对pinned—pinned共振频率影响较大，对其他共振频率点的影响较小。

近地面折射率结构常数的长期测量和统计分析

统计分析了 1997～ 2 0 0 0年合肥地区一复杂地形处近地面折射率结构常数 C2n 的测量数据。给出了不同下垫面、不同季节、不同高度上 C2n 的统计结果。白天 C2n 强弱依次为 6月、5月、4月、9月、1月。白天水面上 C2n 比草地上小 ,夜间比草地上大。不论白天还是夜晚 ,近地面 C2n都随高度递减 ,且 3～10 m高的 C2n 递减较慢 ,10～ 15 m高的 C2n 递减较快。C2n随月份的日变化与模式计算结果基本一致。