PDC钻头谐振冲击作用力对岩石破碎分析研究

随着油气钻探作业从浅层向深层迈进,PDC钻头在钻井过程中遇到的阻碍逐渐增多。提高钻井速度和提升油气生产效率是关键,在钻遇坚硬岩石时,钻头的破岩效率尤为重要。通过PDC钻头谐振破岩技术可有效提升钻井生产效率,该技术是未来钻井技术的发展方向。采用有限元仿真,首先对PDC钻头在有无谐振冲击力作用下,对岩石的破碎效果进行对比,得出PDC钻头具有谐振冲击力的破岩效率更高,并根据不同谐振频率冲击力作用下的岩石破碎程度对比,得出了当谐振频率为60Hz时,PDC钻头的破碎效果最优。

采煤机截齿截割破岩能力分析研究

随着我国经济的飞速发展,在煤矿领域中的生产技术手段也随之有了巨大提升。由于传统的煤炭开采方式过于落后,致使工作人员挖采效率低下,并且容易在过深的煤矿井下出现生产问题。基于此,综合机械化的采煤机应运而生。只有通过人工结合机器进行开采,才能保障煤矿业高效稳定的开发。本文将详细讲述关于采煤机截齿截割破岩能力分析研究的必要性及出现问题后提出相关解决措施。

地下沉积型磷矿悬臂式掘进机机械采掘试验研究

为解决某沉积型地下磷矿矿山开采遇到的成本高、效率低、安全风险大等问题,提出了机械落矿代替传统钻爆法落矿的技术思想,采用悬臂式掘进机进行机械采掘试验研究。首先根据矿山基本概况进行机械破岩可行性分析,选择合适的悬臂式掘进机装备进行落矿试验。然后对试验期间悬臂式掘进机的回采情况、设备运行指标及经济指标进行了详细测算与分析。试验结果证明,该技术适配沉积型地下磷矿的生产需求,可以有效解决开采过程中遇到的生产难题。研究成果具有重要的实用价值和意义。

Blasting induced dynamic stress concentration and failure characteristics of deep-buried rock tunnel

In this study,the dynamic stress concentration factors(DSCF)around a straight-wall arch tunnel(SWAT)were solved analytically utilizing the complex variable function methods and Duhamel’s integral.The effects of wavelength,incident angle,and blasting rising time on the DSCF distribution were analyzed.Theoretical results pointed out dynamic disturbances resulting in compressive stress concentration in the vertical direction and tensile stress in the incident direction.As the wavelength and rising time increased,there was a tendency for the amplitude of stress concentration to initially rise and then converge.Moreover,a series of 3D FEM models were established to evaluate the effect of different initial stress states on the dynamic failure of the tunnel surrounding rock.The results indicated that the failure of the surrounding rock was significantly influenced by the direction of the static maximum principal stress and the direction of the dynamic disturbance.Under the coupling of static and blasting loading,damage around the tunnel was more prone to occur in the dynamic and static stress concentration coincidence zone.Finally,the damage modes of rock tunnel under static stress and blasting disturbance from different directions were summarized and a proposed support system was presented.The results reveal the mechanisms of deep-buried rock tunnel destruction and dynamically triggered rockburst.

An early warning method for water inrush in Dongjiahe coal mine based on microseismic moment tensor

Dongjiahe Coal Mine belongs to the Carboniferous Permian coal field which has a high degree of karst and fissure development.This paper takes the working face of Dongjiahe Coal Mine as an example;through the microseismic(MS)monitoring system arranged on the working face,the moment tensor theory was used to invert the focal mechanism solution of the anomalous area of the floor MS event;combining the numerical simulation and field data,the underlying floor faults were identified by the stress inversion method.The results show that:1)Moment tensors were decomposed into three components and the main type of rupture in this area is mixed failure according to the relative criterion;2)The hidden fault belongs to the reversed fault,its dip angle is approximately 70°,and the rupture length is 21 m determined by the inversion method of the initial dynamic polarity and stress in the focal mechanism;3)The failure process of the fault is divided into three stages by numerical simulation method combined with the temporal and spatial distribution of MS events.The results can provide a reference for early warning and evaluation of similar coal mine water inrush risks.

Analyses and predictions of rock cuttabilities under different confining stresses and rock properties based on rock indentation tests by conical pick

The rock indentation tests by a conical pick were conducted to investigate the rock cuttability correlated to confining stress conditions and rock strength.Based on the test results,the regression analyses,support vector machine(SVM)and generalized regression neural network(GRNN)were used to find the relationship among rock cuttability,uniaxial confining stress applied to rock,uniaxial compressive strength(UCS)and tensile strength of rock material.It was found that the regression and SVM-based models can accurately reflect the variation law of rock cuttability,which presented decreases followed by increases with the increase in uniaxial confining stress and the negative correlation to UCS and tensile strength of rock material.Based on prediction models for revealing the optimal stress condition and determining the cutting parameters,the axial boom roadheader with many conical picks mounted was satisfactorily utilized to perform rock cutting in hard phosphate rock around pillar.

Application of discrete wavelet operations in the detection of acoustic emission of coal and rock rupture

Through the 5-channel SWAES digital full waveform AE detector, the paper dealt with the fracture process of coal and rock samples under uniaxial compression. Using wavelet operations of multi-scale discrete analysis the pulses of a particular time period （points） and the space domain signal by numerical method were gotten, and the paper concluded that the signal singularity in load rupture had closely relations with fracture and uniaxial compression. The detected position and the actual breaking point only differed at one sample point, the relative error was 6.82%, and there was no accumulative error. Thus it provided an effective method to solve the problem of instability analysis of the signal singularity detection and coal-rock compression failure in the whole process.

Frequency spectrum analysis on micro-seismic signal of rock bursts induced by dynamic disturbance

Blasting and breaking of hard roof are main inducing causes of rock bursts in coal mines with danger of rock burst,and it is important to find out the frequency spectrum distribution laws of these dynamic stress waves and rock burst waves for researching the mechanism of rock burst.In this paper,Fourier transform as a micro-seismic signal conversion method of amplitude-time character to amplitude-frequency character is used to analyze the frequency spectrum characters of micro-seismic signal of blasting,hard roof breaking and rock bursts induced by the dynamic disturbance in order to find out the difference and relativity of different signals.The results indicate that blasting and breaking of hard roof are high frequency signals,and the peak values of dominant frequency of the signals are single.However,the results indicate that the rock bursts induced by the dynamic disturbance are low frequency signals,and there are two obvious peak values in the amplitude-frequency curve witch shows that the signals of rock bursts are superposition of low frequency signals and high frequency signals.The research conclusions prove that dynamic disturbance is necessary condition for rock bursts,and the conclusions provide a new way to research the mechanism of rock bursts.

The research of mine rock burst hazard identification based on fault tree analysis

In order to identify the rock burst hazard in coalmine and thus to give a credible forecast, firstly, analyzed such effect factors as natural geological factors and mining technological conditions based on the investigation of more than one hundred mine rock burst cases. Secondly, adopted the fault tree analysis （FTA） technology to the mine rock burst hazard identification for the first time and confirmed twelve kinds of basic events, that is, the large mining depth, the burst-orientation coal seams, the solid strata of roof and bottom, near the faults with bigger fall, the folds, the change of seam thickness, other regional tectonics transformation or stress strip, the drilling, blasting and extracting operation, the unscientific extracting methods, the illogical extracting sequence, the residual pillars and the too close distance between the working face and the residual areas or the stopping extracting lines. Moreover, worked out the fault tree of mine rock burst. At last, it made qualitative analysis and quantitative analysis and forecasted the rock burst hazard according to the characteristic of geologic structure and exploitation technology conditions in certain mine of Shandong Province, China, the rock burst accidents happened in the following exploitation validated that it is of feasibility and veracity adopting FTA to identify the mine rock burst hazard.

Limit variation analysis of shallow rectangular tunnels collapsing with double-layer rock mass based on a three-dimensional failure mechanism

In the framework of upper bound theorem of limit analysis, the progressive collapse of shallow rectangular tunnels with double-layer rock mass has been theoretically analyzed based on the three-dimensional (3D) velocity discontinuity surfaces. According to the virtual work principle, the difference theorem and the variation method, the collapse surface of double-layer rock mass is determined based on the Hoek-Brown failure criterion. The formula can be degenerated to a single-layer rock collapsing problem when the rock mass is homogeneous. To estimate the validity of the result, the numerical simulation software PLAXIS 3D is used to simulate the collapse of shallow tunnels with double-layer rock mass, and the comparative analysis shows that numerical results are in good agreement with upper-bound solutions. According to the results of parametric analysis, the potential range of collapse of a double-layer rock mass above a shallow cavity decreases with a decrease in A1/A2,σci1/σci2 and σtm1/σtm2 and an increase in B1/B2,γ1/γ2. The range will decrease with a decrease in support pressure q and increase with a decrease in surface overload σs. Therefore, reinforced supporting is beneficial to improve the stability of the cavity during actual construction.

Breakability analysis of the elastic rock beam based on the winkler model

Based on the Winkler model, a mechanic model was established with formulas derived concerned with the deformations before and after a roof breakage at places in front of and at the back of the working face. In accordance with the theory for rock beam breakage, the beam breaking position in front of the working face is specified. In addition, the formulas were developed for the velocity of the subsidence at observatory point A in front of the working face when the coal wall serves as the coordinate center and the advance distance at time t as the dynamic coordinate. In the application of the above-mentioned achievements to the practice of Xieqiao Mine and the mines of the Eastern Panji Company of Huainan Mining（Group） Co. Ltd., the results concerned with the velocity with which the roof stratum tends to subside before and after breakage as derived from the mechanic model are well compatible to the results based on in-situ observations and measurements.

Swelling and breaking characteristics of limestone under high temperatures

The elemental composition,heat expansibility and breaking characteristics of limestone have been investigated with the use of an energy spectrum analyzer,a SEM,an optical microscope and an experimental heat swelling power system.The results show that 1) the heat expansibility of limestone has anisotropic properties,and 2) the heat expansion rate in the direction perpendicular to stratification is eight times greater than the rate parallel to stratification.The changes in heat expansibility as a function of heating temperature is essentially coincident with that of swelling and breaking of mineral particles and the appearance of cracks,indicating that the reason for causing the heat expansion of rock are the structural changes of limestone caused by thermal stress,crystal transformation and mineral decomposition.The apparent destruction of limestone under high temperatures is largely characterized by rock stratification breaks.When the limestone is heated beyond a certain limit,the rock destroys into crazed cracks.

Nonlinear creep damage model for soft rock under uniaxial compression

A nonlinear creep-damage model for soft rock under uniaxial compression waspresented,which takes into account both nonlinear creep and damage growth with time.The model is based on the hardening theory,The model is validated through comparisonwith experimental results.

Finite element analysis for blasting law of jointed rock mass

On the basis of Mises strength theory,rock models are built including vertical,horizontal and diagonal joints to simulate jointed rock mass under blasting load by using FEM. The dynamic procedures of jointed rock mass under blasting are quantified and the effective stress-time curves of typical elements are compared to analyze the barrier of joints to the stress wave. The blasting law was studied according to the process of computer simulation and the effect of blasting,and some suggestions were given for solving the problems of overbreak and underbreak.

Discontinuous deformation and displacement analysis: From continuous to discontinuous

A discontinuous deformation and displacement(DDD) analysis method is proposed for modelling the rock failure process. This method combines the rock failure process analysis(RFPA) method(based on finite element method) and discontinuous deformation analysis(DDA) method. RFPA is used to simulate crack initiation, propagation and coalescence processes of rock during the small deformation state. The DDA method is used to simulate the movement of blocks created by the multiple cracks modelled by the RFPA. The newly developed DDD method is particularly suitable for modelling both crack propagation and block movement during the rock failure process because of the natural and convenient coupling of continuous and discontinuous deformation analyses. The proposed method has been used to simulate crack initiation, propagation and coalescence within a slope as well as the block movement during the landslide process. Numerical modelling results indicate that the proposed DDD method can automatically simulate crack propagation and block movement during the rock failure process without degrading accuracy.

A new method of block shape classification

The shapes of block within the rock mass have an important effect on the rock properties, so it＇s very important to evaluate the shapes of rock fragmentation and to determine the geometric characteristics distribution of the block. The previous methods to classify rock block shape are based on the assumption that a block shape is approximately orthogonal, which is acceptable in only a few rock masses. This paper proposes a new method for block shape classification using triangular diagram together with parameters of co-linearity e and volume coefficient K, which combines the shape categorization with block volume for statistical analysis. Rock block equivalent size calculation methods based on block shape is proposed and the block cumulative percentage of total volume statistical analysis is given. In order to verify this block shape classification method, three ideal rock masses with approximately orthogonal joint sets have been generated and simulated.