A Feasibility Study on Controlling Ground Vibrations Caused by Blasts in Malmberget Underground Mine

In order to control or reduce the ground vibrations caused by underground blasts in Malmberget mine, a number of blast tests were carried out during production blasts and a series of single shot waveforms were obtained. Then the single shot waveforms from the same ring or different rings were analysed and compared with each other. The results showed that the single shots are reproducible, meaning that the ground vibrations caused by underground blasts can be controlled by means of the interference of the vibration waveforms measured. Finally, a formal test using electronic detonators and employing an optimum delay time of 8 ms was done in production. The test for an 11-borehole ring shows that the maximum vertical ground vibrations are reduced to the maximum vertical vibrations of a single shot. Particularly, the total vibration history for the 11-borehole-ring blast is shortened to about 200 ms over a velocity of 2 mm/s. However, the total vibration history of a normal production blast of 11-borehole ring is always 1400 ms over a velocity of 2 mm/s, namely the total vibration time of a production blast can be reduced to one seventh of that of the common production blasts by using the vibration control method. This indicates that the vibration control method introduced in the paper is feasible for underground mining blasts.     

Analysis of Ground Vibrations Caused by Open Pit Production Blasts - A Case Study

In order to study the characteristics of ground vibrations caused by production blasts in an open pit gold mine and to evaluate the impact of the vibrations to buildings, a seismic survey was conducted at an open pit mine. Two monitoring lines with multiple seismic stations were surveyed. The first line had a length of 4,492 m and the second line runs approximately perpendicular to the first line with a length of 823 m. The seismographs recorded the particle acceleration, velocity, and displacement in longitudinal, transverse and vertical directions. The magnitudes of peak particle motions were calculated and compared with several established damage criteria used in mining and geotechnical/structure engineering. Empirical equations were established based on the field measurements. Analyses were also performed to exam the effects of geological structures on the attenuation of individual vibration components as well as the peak vector sum of the particle velocity.     

Dynamic Modelling of Fault Slip Induced by Stress Waves due to Stope Production Blasts

Seismic events can take place due to the interaction of stress waves induced by stope production blasts with faults located in close proximity to stopes. The occurrence of such seismic events needs to be controlled to ensure the safety of the mine operators and the underground mine workings. This paper presents the results of a dynamic numerical modelling study of fault slip induced by stress waves resulting from stope production blasts. First, the calibration of a numerical model having a single blast hole is performed using a charge weight scaling law to determine blast pressure and damping coefficient of the rockmass. Subsequently, a numerical model of a typical Canadian metal mine encompassing a fault parallel to a tabular ore deposit is constructed, and the simulation of stope extraction sequence is carried out with static analyses until the fault exhibits slip burst conditions. At that point, the dynamic analysis begins by applying the calibrated blast pressure to the stope wall in the form of velocities generated by the blast holes. It is shown from the results obtained from the dynamic analysis that the stress waves reflected on the fault create a drop of normal stresses acting on the fault, which produces a reduction in shear stresses while resulting in fault slip. The influence of blast sequences on the behaviour of the fault is also examined assuming several types of blast sequences. Comparison of the blast sequence simulation results indicates that performing simultaneous blasts symmetrically induces the same level of seismic events as separate blasts, although seismic energy is more rapidly released when blasts are performed symmetrically. On the other hand when nine blast holes are blasted simultaneously, a large seismic event is induced, compared to the other two blasts. It is concluded that the separate blasts might be employed under the adopted geological conditions. The developed methodology and procedure to arrive at an ideal blast sequence can be applied to other mines where faults are found in the vicinity of stopes.     

Ground Vibration due to Blasting in Limestone Quarries

A database of ground vibration due to blasting at 27 limestone quarries, located in various parts of India, has been created. The database contains peak particle velocity (PPV), frequency, other vibration related and blast design parameters. Regression analysis of the data is carried out to derive site constants of the USBM predictor equation for individual quarries. It is found that these site constants are correlated with each other. By combining all the data, a generalised predictor equation is developed to assess and control ground vibration. In addition, mean zone of attenuation has been delineated using the predictor equations of the individual quarries. The dominant frequency of ground vibration with respect to distance and the possibility of modifying it by changing delay intervals in production blasts are also examined.     

X射线荧光光谱法分析不同类型岩石中10种主量元素的测试能力验证

以28个不同类型岩石标样作外标,用玻璃熔片法制样,采用经验系数法进行基体校正,建立了X射线荧光光谱法(XRF)测定不同类型岩石中硅铝钙镁等10种主量元素的分析方法。该方法被用于参与GeoPT分析测试能力验证,15年来分析了23个不同类型的岩石验证样品。经验证该方法对SiO_2、Al_2O_3、K_2O和CaO具有非常好的分析效果(所有测定结果的|Z|2);对于MgO、MnO、TiO_2和Na_2O四个元素,尽管各有一个样品的分析结果的|Z|2,这主要是样品与标样的基体差异较大造成了低含量样品测定结果超差,但依然可获得好的分析效果;当TFe_2O_31.0%,P_2O_5含量在0.08%~0.80%区间时,分析结果的|Z|2,满足分析期望。总体上所建立的XRF分析方法稳定,可满足应用地球化学实验室测试不同类型岩石中10种主量元素的分析期望。     

高原冻土区不同下垫面的附面层研究

下垫面附面层中的热量交换和水分交换是大气与地面间的热质交换现象的集中反映。笔者导出一个气温与下垫面附面层底面温度直接相关的方程,从而可较为方便地确定热量的上边界条件。还从理论上导出适用于不同基本参数的近似解并揭示了长期观测资料的物理意义。     

Ground motion amplification due to shallow cavities in nonlinear soils

Subsurface cavities or stiff inclusions represent mechanical discontinuities for seismic waves propagating in soils. They modify the propagation pattern of seismic waves and alter soil response in correspondence to the ground level or building foundations. In the literature, different analytical and numerical solutions have been proposed to account for the effect of underground cavities or inclusions on the motion generated by P, S or R waves. In these former studies, the subsoil was assimilated to a homogeneous, isotropic and linear elastic halfspace containing one or more cavities. In the present study, the effect of subsurface cavities on ground motion amplification has been analysed accounting for soil stiffness degradation and associated damping increase with increasing levels of shear strains, a fundamental aspect of soil behaviour under earthquakes. The analysed model was inspired to a real case represented by the village of Castelnuovo (Italy), which during the 2009 Abruzzo earthquake suffered huge damage. The main shock (6 April 2009) caused the collapse of 50 % of the whole built environment. The historical centre of Castelnuovo rises on a hill. In its subsoil, there are many cavities with roofs 2–3 m below the ground level. The longitudinal NW–SE section of the hill has been investigated by 2D nonlinear site response analyses. A preliminary site response analysis was performed without modelling cavities, to identify ground motion amplification due to mere stratigraphic and topographic factors. The numerical model was later refined inserting: (1) a single cavity below the hilltop, (2) multiple cavities placed below the ground surface of the hill and (3) multiple cavities filled with concrete (inclusions). The performed study highlights the important role exerted by underground cavities on the ground motion computed at the hill surface. This effect should be properly considered for both microzonation studies and the correct determination of the seismic actions on specific buildings.     

Dissimilarity of Continental and Oceanic Rock Types

Recent papers, cite the similarity of rocks, particularly andesites,in continental and oceanic regions, but the similarity is primarilyone of name. The oceanic ‘andesites’ belong to thealkaline suite, whereas the typical continental andesitesarecalc alkaline and hypersthene-or hornblende-bearing. To avoidfurther confusion it is suggested that the name ‘andesite’for the oceanic rocks be replaced by the names hawaiite andmugearite. Whatever name is used, it is essential to emphasizethe difference between the oceanic ‘andesites’ andthe andesites of continental orogenic regions. All members of the oceanic suite are present also in continentalregions, but the calc alkaline rocks characteristic of orogenicregions on the continents are absent within the true ocean basins,except in island arcs near the continets that were formerlyregarded as the continental border.     

A Study on Crack Damage Stress Thresholds of Different Rock Types Based on Uniaxial Compression Tests

When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress σ _cc, crack initiation stress σ _ci, crack damage stress σ _cd, and uniaxial compressive strength σ _ucs; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress σ _cd, its threshold, and a possible relationship between σ _cd and the uniaxial compressive strength. The σ _cd of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in σ _cd /σ _ucs between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average σ _cd /σ _ucs resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on σ _cd /σ _ucs. The ratio σ _cd/σ _ucs could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.     

Satellite-Derived Regional Apparent Thermal Inertia and Gravity for Mapping Different Rock Types in Parts of Banswara,Rajasthan

The present study deals with the delineation of lineaments over Sir Creek offshore and its surroundings from EGM2008 gravity data using various derivative techniques owing to their costeffectiveness in prospective hydrocarbon exploration. Initially, 2-D and 3-D synthetic models have been generated with vertical prismatic objects at different depths. The effectiveness of total horizontal derivative (THD) technique has been established by comparing with E-W and N-S Horizontal derivatives and First Vertical derivative techniques. The residuals of Bouguer gravity data have been estimated with different cut-off wavelengths. Further, the residual anomaly map has been enhanced by the derivative techniques for the delineation of the structural features. Possible depths of the delineated lineaments have been estimated using Euler deconvolution of the Bouguer gravity data, which indicates maximum clustering over the delineated lineaments. It is observed that most of the lineaments are in the depth range of 1.0 km to 5.5km, which correlate well with the previous seismic studies. The present study reveals that the major lineament trends in the N-S, E-W and NNW-SSE directions followed by NE-SW, NW-SE and ENE-WSW directions. These major lineament trends are due to the tectonic activities occurred during Precambrian and Cretaceous period. Different small circular features, rectangular features and shorter wavelength features have also been identified, which could be the key parameter for mapping potential location for hydrocarbon exploration.     

The Shear Behavior of Bedding Planes of Weakness Between Two Different Rock Types with High Strength Difference

In this article, the shear behavior of discontinuities caused by bedding planes of weakness between two different rock types with high strength difference is investigated. The effect of roughness and compressive strength of joint wall in such discontinuities are studied. The designed profiles consist of two regular and three irregular artificial joints molded by three types of plaster mortars with different uniaxial compressive strengths. Firstly, it is demonstrated that the shear behavior of discontinuities with different joint wall compressive strengths (JCS) is different from rock joints with identical wall compressive strengths by showing that Barton’s empirical criterion is not appropriate for the former discontinuities. After that, some correlation equations are proposed between the joint roughness coefficient (JRC) parameter and some surface statistical/fractal parameters, and the normal stress range of Barton’s strength criterion is also modified to be used for such discontinuities. Then, a new empirical criterion is proposed for these discontinuities in such a way that a rational function is used instead of JRC log₁₀(JCS/σ _n) as i ₀(σ _c/σ _n)^a/[b + (σ _c/σ _n) ^a ] by satisfying the peak dilation angle boundary conditions under zero and very high normal stress (physical infinite normal stress causing zero peak dilation angle). The proposed criterion has three surface parameters: i ₀, a, and b. The reason for separation of i ₀ from JRC is indicated and the method of its calculation is mentioned based on the literature. The two remaining coefficients (a and b) are discussed in detail and it is shown that a shows a power-law relationship with b, introducing the coefficient c through b = c ^a . Then, it is expressed that a is directly related to discontinuity surface topography. Finally, it is shown that the coefficient c has higher values in irregular profiles in comparison with regular profiles and is dominated by intensity of peak dilation angle reduction (majorly related to the surface irregularity and minorly related to roughness). The coefficient c is to be determined by performing regression analysis on experimental data.     

Response of Concrete and Masonry Dams to Ground Vibration due to Blasting

The safety and stability of concrete and masonry dams is a great concern when blasting has to be conducted close to these dams in order to construct small hydro-electric projects. There is a danger of ground vibration amplification to those residential-type buildings that are built close to these dams.

Responses of three concrete and masonry dams were measured directly by conducting a number of blasts and by monitoring vibration in the ground as well as on the dams. The amplitudes and frequencies of the motions were analysed and vibration attenuation relations were derived. These relations were used to compare the vibration levels on the dams with those in the ground.

Because of close-in construction blasts that produced high frequency ground vibrations, there was no amplification of the ground vibrations by these dams. The measured amplitudes of ground vibration were comparable to those of the dams.     

Dissimilarity of Continental and Oceanic Rock Types1

Recent papers cite the similarity of rocks, particularly andesites,in continental and oceanic regions, but the similarity is primarilyone of name. The oceanic ‘andesites’ belong to thealkaline suite, whereas the typical continental andesites arecalc alkaline and hyperstheneor hornblende-bearing. To avoidfurther confusion it is suggested that the name ‘andesite’for the oceanic rocks be replaced by the names hawaiite andmugearite. Whatever name is used, it is essential to emphasizethe difference between the oceanic ‘andesites’ andthe andesites of continental orogenic regions. All members of the oceanic suite are present also in continentalregions, but the calc alkaline rocks characteristic of orogenicregions on the continents are absent within the true ocean basins,except in island arcs near the continents that were formerlyregarded as the continental border.     

中国磷矿资源需求预测

世界上约66%的磷矿石用于生产磷肥,磷矿的合理开采和利用直接关系国家粮食安全以及人类的生存发展,磷矿工业的可持续发展对化肥工业和农业生产均具有重要意义。本文通过对典型工业化国家人均磷肥消费与人均GDP倒"U"形规律的分析,结合我国历史磷肥消费状况、氮磷钾科学施肥比例以及未来经济发展趋势,分三种经济增长情景(即高增长、参考和低增长)对我国未来的磷肥需求进行预测,并根据磷矿消费结构,进一步估算了磷矿资源的需求。根据本研究的预测结果,中国磷肥需求峰值预计可能在2020—2025年到来,届时磷肥需求可能达到1700~1800万吨(折P2O5100%),磷矿石需求总量可能达到2000~2100万吨(折P2O5100%)。这一预测结果将会对指导磷肥的合理施用,以及磷矿的可持续开发利用起到积极作用。     

滕沛煤田地下水的类型及其特征

据已有资料,对鲁西南、苏北煤炭开发区的矿床水文地质条件作了大最分析、研究,指出了与煤矿开采有关的水文地质问题.     

Prediction of sub-surface subsidence movements due to underground coal mining

Summary The theoretical model of the relationship between sub-surface and surface subsidence movements proposed earlier by the authors of this paper is briefly described and further tested against another case history example. Using this model, the magnitudes of the maximum subsidence, tilt and horizontal strain at sub-surface horizons between the ground surface and seam level are predicted in terms of the magnitudes of the corresponding components at the surface due to the extraction of subcritical panels with a wide range of width-depth ratios and the results presented in the form of nomographs and tables. These graphs and tables could be used to estimate the maximum subsidence, tilt and horizontal strain at any chosen sub-surface horizon associated with the extraction of a subcritical panel from the known corresponding maximum values at the surface.The proposed theoretical model can also be used to predict sub-surface subsidence components at any point within the zone influenced by the extraction of a panel from the corresponding surface subsidence components which may be obtained from field measurements or pre-calculated using any existing method of surface subsidence prediction. As an example, the profiles of surface and sub-surface subsidence at various horizons between the ground surface and the seam level resulting from the extraction of an assumed sub-critical longwall panel are predicted using the theoretical model together with the empirical method of surface subsidence prediction. The pattern of sub-surface subsidence movements in the strata overlying the panel is examined.     

Prediction of tidal excursion length in estuaries due to the environmental changes

Tidal excursion is an important parameter that indicates hydraulic and mixing characteristics of estuarine environments. Prediction of the tidal excursion length provides a proper tool for environmental management of estuaries. In this study, the governing equations of the salinity transport were scaled first to recognize the effective dimensionless parameters of tidal excursion length. Then, a laterally averaged two-dimensional numerical model called CE-QUAL-W2 was used as a virtual laboratory to simulate the salinity intrusion length. Existing field data of Limpopo estuary, as a case study, was used for calibration and verification of the model and reasonable agreement was observed between the model results and the field data. Finally, the verified model was used to assess the influences of the governing parameters. The results showed that simple power functions can be used to describe the effects of dimensionless parameters obtained by scaling of the governing equations. As a result, a new formula in form of a power function was derived to predict the tidal excursion length based on the geometric and hydrodynamic characteristics of alluvial estuaries. Comparison of the computed tidal excursion lengths using the derived formula with the observed measurements in several estuaries showed the robustness of the developed formula.     

江汉平原主要河流沉积物磁学特征及其与物源区表壳岩性的响应

为了建立江汉平原沉积物示踪的磁学模型,对汇入江汉平原的主要河流现代沉积物磁学特征进行了研究,结果表明:(1)在江汉平原范围内,无论长江、汉江,还是周边的漳河、沮水、玛瑙河和清江,它们的现代沉积物的磁学参数特征均显示出明显的差异,而且和源区表壳岩性也显示出极好的相关性;(2)长江和汉江现代沉积物中铁磁性矿物均以亚铁磁性矿物为主,它们主导了样品的磁性特征,但长江沉积物比汉江沉积物亚铁磁性矿物含量高;(3)长江和汉江沉积物的亚铁磁性矿物晶粒都以假单畴-多畴为主,并且长江沉积物磁性颗粒总体上要比汉江的粗;(4)在汇入江汉平原的主要支流中,汉江的亚铁磁性矿物含量远远高于其他支流,且磁性矿物的晶粒也比其他支流的粗;(5)除汉江以外的支流中,玛瑙河沉积物中磁性矿物的晶粒比较细且不完全反铁磁性矿物含量较高,漳河中的超顺磁物质含量较高,而清江中不完全反铁磁性矿物含量较高且磁性矿物的晶粒相对较粗.上述结果表明,在江汉平原利用沉积物的磁学特征可达到沉积物物源示踪的目的.