Investigation on strength and stability of jointed rock mass using three‐dimensional numerical manifold method

This paper proposes a numerical model for jointed rock masses within the 3‐D numerical manifold method (NMM) framework equipped with a customized contact algorithm. The strength of rock sample containing a few sets of discontinuities is first investigated. The results of models with simple geometries are compared with the available analytical solutions to verify the developed computer code, whereas models with complex geometries are simulated to better understand the fundamental behavior and failure mechanism of jointed rock mass. Furthermore, the stability of jointed rock mass in an underground excavation is studied, where rock failure process is determined by the 3‐D NMM simulation. The simulation results provide valuable guidance on excavation process design and stabilization design in rock engineering practice. Copyright © 2012 John Wiley & Sons, Ltd.     

北秦岭火山岩岩石化学特征和成因

北秦岭存在A、B、C三类火山岩系列,对应着幔源型、壳幔混染型和壳幔混合型成因类型。火山岩系列和成因类型的系统变化,反映了多旋回壳幔物质迁移特证。     

胶东牟平—乳山地区花岗岩副矿物特征及其成因

本文论述了牟平—乳山地区花岗岩的岩石学特征,副矿物组合特征,尤其是锆石特征,副矿物的化学成分与微量元素及稀土元素组合特征,并在此基础上探讨了花岗岩的成因。本区花岗岩的成因是复杂的,既有花岗岩化作用(交代作用)和深熔作用形成的花岗岩,又有岩浆分异结晶作用的产物。     

Paleomagnetic Excursions Recorded in the Yanchi Playa in Middle Hexi Corridor, NW China Since the Last Interglacial

Paleomagnetic determinations on lithologieal profiles of two paralleled long drillin gcores covering the past 130 kyr B.P., GT40 and GT60,from the Yanchi Playa in the arid Northwestern China indicate that a series of pronounced paleomagnetic excursions have been documented. By correlating our results with published regional and worldwide reports 4 excursion events out of 10 apparent reversal signals (labeled from GT-1 to GT-10) were identified as excursion events coeval with the Mono Lake Event (28.4 kyr-25.8 kyr), Laschamp Event (43.3 kyr-40.5kyr), Gaotai Event (82.8 kyr-72.4 kyr) and the Blake Event (127.4 kyr-113.3 kyr), respectively. GT-9 correlates with the above-mentioned Gaotai Event,GT-7 and GT-6 correspond to two stages of the Laschamp Event and GT-5 to the Mono Lake Event. It is noteworthy that the so-called Gaotai Event has not been reported as a pronounced paleomagnetic excursion in the Northwestern China. Every magnetic excursion event corresponds to paleointensity minima, anteceding those established abrupt paleoclimatic change events, such as the Younger Drays and the Heinrich Events (H1-H6). Here, we tentatively propose that these geomagnetic excursions/reversals can be viewed as precursors to climate abruptness. During the transitional stages when the earth‘s magnetic field shifted between a temporal normal and a negative period, the earth‘s magnetic paleointensity fell correspondingly to a pair of minima. Although more precise chronology and more convincing rock magnetic parameter determinations are essentially required for further interpretation of their intricate coupling mechanism, these results may have revealed, to some extent, that the earth‘s incessantly changing magnetic field exerts an strong influence on the onset of saw-tooth shaped abrupt climate oscillations through certain feedback chains in arid Central Asia or even North Hemispheric high latitude regions.     

论辽南上前寒武系的划分与对比

辽南上元古界的区域对比的关键是如何与蓟县层型、峡东层型的衔接或对比。作者认为辽南群是介于北方的青白口群与南方的震旦系之间的层位，仅金县群才相当于震旦系，震旦系与寒武系的界线则应置于兴民村组与葛屯组之间。     

CR21气象仪的CS-1型串行接口转换器

CR 21气象仪的SC 1串行接口与标准的RS 232接口并不兼容,难以并入滑坡遥测系统。对此特研制CS-1型串行接口转换器。它能使SC 1串行接口电平与标准的RS 232接口电平彼此转换。由此在微型计算机专用软件支持下,CR 21气象仪便能自动而又准确地向滑坡遥测系统传输数据。     

A grid-based tropospheric product for China using a GNSS network

Tropospheric delay accounts for one source of error in global navigation satellite systems (GNSS). To better characterize the tropospheric delays in the temporal and spatial domain and facilitate the safety-critical use of GNSS across China, a method is proposed to generate a grid-based tropospheric product (GTP) using the GNSS network with an empirical tropospheric model, known as IGGtrop. The prototype system generates the GTPs in post-processing and real-time modes and is based on the undifferenced and uncombined precise point positioning (UU-PPP) technique. GTPs are constructed for a grid form (\(2.0{^{\circ }}\times 2.5{^{\circ }}\) latitude–longitude) over China with a time resolution of 5 min. The real-time GTP messages are encoded in a self-defined RTCM3 format and broadcast to users using NTRIP (networked transport of RTCM via internet protocol), which enables efficient and safe transmission to real-time users. Our approach for GTP generation consists of three sequential steps. In the first step, GNSS-derived zenith tropospheric delays (ZTDs) for a network of GNSS stations are estimated using UU-PPP. In the second step, vertical adjustments for the GNSS-derived ZTDs are applied to address the height differences between the GNSS stations and grid points. The ZTD height corrections are provided by the IGGtrop model. Finally, an inverse distance weighting method is used to interpolate the GNSS-derived ZTDs from the surrounding GNSS stations to the location of the grid point. A total of 210 global positioning system (GPS) stations from the crustal movement observation network of China are used to generate the GTPs in both post-processing and real-time modes. The accuracies of the GTPs are assessed against with ERA-Interim-derived ZTDs and the GPS-derived ZTDs at 12 test GPS stations, respectively. The results show that the post-processing and real-time GTPs can provide the ZTDs with accuracies of 1.4 and 1.8 cm, respectively. We also apply the GTPs in real-time kinematic GPS PPP, and the results show that the convergence time of the PPP solutions is shortened. These results confirm that the GTPs can act as an efficient information source to augment GNSS positioning over China.     

粤东莲花山地区锡矿矿产类型

锡矿是粤东优势矿种之一。在收集分析粤东莲花山地区61个锡矿床（点）成矿特征的基础上,对该地区锡矿床（点）矿产类型进行划分归类,建立了粤东莲花山地区锡矿工业类型,主要有为锡石-硫化物型、锡石-硅酸盐型、锡石-石英脉型、斑岩型4类;对4种不同类型锡矿床所具有的矿物组合进行归纳,并开展各类型代表性矿床综合研究,初步构建了4个类型代表性矿区的成矿模式图,为粤东地区锡矿研究提供了基础资料。     

Rapid report of the 8 January 2022 ​MS 6.9 Menyuan earthquake,Qinghai, China

The M_S 6.9 Menyuan earthquake in Qinghai Province, west China is the largest earthquake by far in 2022. The earthquake occurs in a tectonically active region, with a background b-value of 0.87 within 100 ?km of the epicenter that we derived from the unified catalog produced by China Earthquake Networks Center since late 2008. Field surveys have revealed surface ruptures extending 22 ?km along strike, with a maximum ground displacement of 2.1 ?m. We construct a finite fault model with constraints from InSAR observations, which showed multiple fault segments during the Menyuan earthquake. The major slip asperity is confined within 10 ?km at depth, with the maximum slip of 3.5 ?m. Near real-time back-projection results of coseismic radiation indicate a northwest propagating rupture that lasted for ～10 ?s. Intensity estimates from the back-projection results show up to a Mercalli scale of IX near the ruptured area, consistent with instrumental measurements and the observations from the field surveys. Aftershock locations (up to January 21, 2022) exhibit two segments, extending to ～20 ?km in depth. The largest one reaches M_S 5.3, locating near the eastern end of the aftershock zone. Although the location and the approximate magnitude of the mainshock had been indicated by previous studies based on paleoearthquake records and seismic gap, as well as estimated stressing rate on faults, significant surface-breaching rupture leads to severe damage of the high-speed railway system, which poses a challenge in accurately assessing earthquake hazards and risks, and thus demands further investigations of the rupture behaviors for crustal earthquakes.