A numerical study on 2-D compressive wave propagation in rock masses with a set of joints along the radial direction normal to the joints

An explosion in a borehole or an accidental explosion in a tunnel will generate a two-dimensional (2-D) compressive wave that travels through the surrounding rock mass. For the problem of 2-D compressive wave propagation in a rock mass with parallel joints in the radial direction normal to the joints, parametric studies on the transmission ratio and the maximum rebound ratio are performed in universal distinct element code. The variation of the transmission ratio with the ratio of joint spacing to wavelength is generalized into a characteristic curve, which can be used as a prediction model for estimating the transmission ratio. The relationship between the maximum rebound ratio and the influence factors is obtained in charts. The charts can be used as a prediction model for estimating the maximum rebound ratio. The proposed prediction models for estimating the transmission ratio and the maximum rebound ratio are applied to a field explosion test, Mandai test in Singapore. The minimum possible values of peak particle velocity (PPV) at the monitoring points are estimated by using the proposed prediction model for estimating the transmission ratio along the radial direction normal to the joints. On the other hand, the maximum possible values of PPV are estimated by using the proposed prediction model for estimating the maximum rebound ratio along the same radial direction. The comparison shows a good agreement between the field-recorded PPVs and the estimated range of PPVs given by the minimum possible PPVs and the maximum possible PPVs at the monitoring points in Mandai test. The good agreement between the estimated and field-recorded values validates the proposed prediction models for estimating peak particle velocity in a rock mass with a set of joints due to application of a compressive wave at the boundary of a tunnel or a borehole.     

Analysis of rock drainage and cooling experiments for underground cryogenic LNG storage

Hydrogeological monitoring was conducted around a pilot cavern for underground cryogenic LNG (Liquefied Natural Gas) storage. The monitoring was mainly focused on the operation of a drainage and recharge system. After the operation of the drainage system commenced, the drainage rate decreased rapidly in the initial stages and then decreased gradually. Hydrogeological monitoring revealed that the rock drainage system operated effectively. During drainage, the water table was maintained below the cavern roof. The recharge for ice-ring formation was performed in two phases. The first phase involved the cessation of pumping in downward-drainage holes and the second involved the closure of upward boreholes. Since the water table was maintained below the cavern roof, artificial recharge was planned at first. However, it was not implemented due to heavy rainfall in the recharge stage. On the basis of hydrogeological monitoring and hydraulic tests, it was found that the fractures above the roof and on the right wall of the pilot cavern mainly affected seepage into the cavern and thermal variation due to the storage of liquid nitrogen. Thermal variation was examined by the thermometers installed around the pilot cavern. The cooling and thawing processes reveal the characteristics of thermal distribution in the rock and the 0 °C isotherm. The cooling phase lasted for six months, and the 0 °C isotherm progressed in time after the injection of liquid nitrogen into the cavern. The isotherm propagated up to about 4 m from the floor and the sidewall of the cavern and about 3 m from the cavern roof. The cooling rate of the rock mass above the cavern roof was lower than that of the other cavern sides due to the gaseous space in the upper part of the containment. The fractures were analyzed and considered for thermal modeling. A two-dimensional finite element analysis was performed to compare the field monitoring at the pilot cavern. The numerical modeling shows the distance between the ice ring and heat transfer pattern of the fractures around the pilot cavern. The propagation of the measured and calculated 0 °C isotherm reveals that the water-conveying joint on the right wall might affect thermal propagation through a thermal pipe.     

甘肃礼县盐关井水位短临异常与滇北强震的关系

在分析了甘肃礼县盐关井水位20多年来的异常变化与邻近地区发生中强地震的对应关系基础上,着重就18年来井水位出现两次较大幅度的负异常与相距1000 km多的云南禄劝1985年6.1级地震和云南大姚2003年6.2级地震的对应关系进行了探讨,认为该井很可能是滇北两个震区强震的“穴位”和灵敏点。     

提高地磁绝对观测数据精度的有效途径

经过长期观察发现用CZM-2型核旋仪(及其同类仪器)进行定点观测读数时,运用分量仪线圈“单向”旋转的方法进行分量观测,再加上做好一些其它辅助措施,能够充分消除人为因素和仪器本身误差所带来的影响,明显提高仪器的观测精度,达到使观测资料更加准确的目的。     

玉溪市萝卜子地水源地地下水允许开采量评价

萝卜子地供水水源地,水文地质条件较复杂。利用多年地下水动态及抽水试验资料上,进行基岩富水地段地下水的补给量计算,以补给量作为该水源地的允许开采量合理。     

曲线拟合在核探测器信号幅度提取中的应用

研究数字化核探测器输出脉冲信号的幅度提取问题。根据闪烁探测器的电路特性，推导了其脉冲信号理想曲线方程。综合利用三和值法、最小二乘法、试探法等方法，设计了该理想曲线拟合算法。由脉冲信号采样点数据，通过曲线拟合，计算出曲线的极大值，该值即为闪烁探测器输出脉冲信号的幅度。正反演数据结果对比表明，采用曲线拟合算法提取闪烁探测器输出脉冲信号幅度，其方案可行，计算结果更准确。相较于数字滤波和数字脉冲成形方法提取核探测器输出脉冲幅度，该算法更简单，对仪器的硬件处理速度要求更低。该方法开辟了核探测器脉冲幅度提取的新途径。     

Double detonations at the core–envelope boundary in Type Ia supernovae

An off-centre detonation propagating near the interface between a C–O core and a He envelope in a Type Ia supernova explosion is modelled as a steady two-dimensional similarity solution at a plane interface. We assume that in both regions the energy release occurs in an infinitely thin detonation, which produces material in nuclear statistical equilibrium (NSE) in He and in nuclear statistical quasi-equilibrium in C–O. An α-network is then used to determine the effect of the associated rarefaction wave in the C–O on the final abundance of intermediate elements. We find that, although there is a significant effect, the rarefaction is not strong enough to quench the reactions and prevent the C–O from burning to NSE.     

矿井导线网空间关系和操作的半序集模型

本文用单纯复形的半序关系和格的数学理论,对矿井导线网的空间关系和操作给予了形式的描述。导线网的细部用半序关系来表示,一般能回答导线网的包含、相邻、相接等空间关系问题,用格的理论能方便地实现导线网的交、并和查询等空间操作。对于非格的半序关系,通过增加新的元素构成格,用序的理论对导线网的结构进行形式描述,为导线网数据和拓扑结构的计算机存储和操作提供理论基础。     

Discrimination of small earthquakes and artificial explosions in the Korean Peninsula using Pg/Lg ratios

The purpose of this study is to develop a technique to discriminate artificial explosions from local small earthquakes ( M ≤ 4.0) in the time–frequency domain. In order to obtain spectral features of artificial explosions and earthquakes, 3-D spectrograms (frequency, time and amplitude) have been used. They represent a useful tool for studying the frequency content of entire seismic waveforms observed at local and regional distances (Kim, Simpson & Richards 1994). P and S(L g ) waves from quarry blasts show that the frequency content associated with the dominant amplitude appears above 10  Hz and Rg phases are observed at close distances. P and S(L g ) waves from the Tongosan earthquake have strong amplitudes below 10  Hz. For the Munkyong earthquake, however, a broader frequency content up to 20  Hz is found.
  For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10  Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20  sps, we cannot avoid analysing below 10  Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10  Hz. The best separation between explosions and earthquakes is observed from 6 to 8  Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH.     

Heavy-element abundances in seven SC stars and several related stars

We employ spectra of resolution 20–35000 of seven SC stars, four S stars, two Ba stars and two K–M stars to derive abundances of a variety of elements from Sr to Eu relative to iron. Special attention is paid to Rb and Tc, and to the ratio of the heavy s-process species to the light s-process elements. Abundances are derived in LTE, both by using model atmospheres in which the carbon and oxygen abundances are nearly equal and by using curves of growth. Spectrum synthesis is used for critical lines such as the 5924-Å line of Tc and the 7800-Å line of Rb. For most of the heavy-element stars the enhancement of the s-process elements is about a factor of 10. The ratio of the heavy to light s-process species is not far from solar, except for RR Her for which the same ratio is +0.45 dex. For Tc the blending by other lines is severe. While we have probably detected the 5924-Å line, we can only present abundances in the less-than-or-equal-to category. For Rb, whose abundance is sensitive to the ⁸⁵Rb/⁸⁷Rb ratio and hence to the neutron density during s-process production, we find a considerable range of abundances, indicating a neutron density from 10⁶ to ≳10⁸ cm⁻³ for the SC stars. For the four S stars the range is from 10⁷ to ≳10⁸ cm⁻³. Recent calculations by Gallino et al. show that neutron densities near 10⁷ cm⁻³ favour the ¹³C source for neutrons, while densities greater than 10⁸ cm⁻³ may be associated with neutrons from the ²²Ne source.