A finite element approach for predicting the full resistance profile of a spudcan deeply penetrating in dense sand overlying clay     

《Applied Ocean Research》2019

This paper presents a finite element approach to calculate the full resistance profile of a spudcan deeply penetrating in dense sand overlying clay, in which a potential for an installing spudcan to experience a sudden uncontrolled punch-through failure exists. A modified Mohr-Coulomb model characterized by incorporating a four-phase variation of the mobilized strength and dilation parameters with an equivalent accumulated plastic strain is developed and tested for the overlying dense silica sand. An extended Tresca model is used for the strain softening of the underlying clay. A series of large deformation finite-element (LDFE) analyses are carried out, varying the strength and dilation parameters as well as the spudcan geometries. A fairly good performance of the present approach is verified by validating against groups of centrifuge tests data, allowing the numerical study to be extended parametrically. The four-phase variation of the mobilized strength and dilation parameters involved in the progressive failure of the upper dense sand is parametrically studied and extended to cover the range of sand relative densities that are of practical interest. Additionally, comparisons with the typical existing LDFE analyses using both simple and sophisticated constitutive models are carried out. It shows that the present approach performs fairly well to calculate the full resistance profile of a spudcan deeply penetration in both thin and thick dense sand overlying clay, especially the peak and post-peak resistance, within around 5% of the corresponding centrifuge tests results.  相似文献   

黑龙江黑宝山-罕达气盆地早白垩世九峰山组年代地层划分     

杨雅军  江斌  王筱筝  庞雪娇  石国明 《地质与资源》2020,29(5):403-410

为了确定黑龙江黑宝山-罕达气盆地九峰山组形成的气候环境及时代，对九峰山组生物地层特征进行了系统的总结与对比.植物及其孢粉化石反映了典型的亚热带潮湿气候环境，时代为早白垩世.对九峰山组下部所夹流纹质凝灰岩进行了LA-ICP-MS锆石U-Pb同位素测年，获得了119±0.89 Ma成岩年龄.综合古生物和同位素年龄确定九峰山组形成于早白垩世阿普特阶中晚期，这一研究成果可为东北地区晚中生代区域性地层、成煤时代、含煤盆地对比提供精确的年代依据.  相似文献   

新疆奇台县黄羊山石墨矿床特征、物质来源及成因     

孙新浩  任云生  孙珍军  李作武  王承洋 《岩石学报》2021,37(6):1867-1882

黄羊山石墨矿床位于新疆东准噶尔造山带南部的卡拉麦里地区东南段,是近年来新发现的国内外首个产于花岗岩体中的超大型石墨矿床。成矿地质条件、矿床地质特征研究表明,该矿床与黄羊山碱性花岗岩体具有密切的时空及成因联系,矿石具独特的球状构造,球体中石墨与长英质矿物及磁黄铁矿、黄铜矿等金属硫化物密切共生。为确定黄羊山石墨矿床的成因和成矿物质来源,本文开展了球状矿石中的石墨拉曼光谱分析和C同位素测试,对与石墨密切共生的金属硫化物开展S-Pb同位素分析。结果表明,黄羊山矿床球状矿石不同部位石墨的拉曼谱峰相似,显示具有很高的结晶程度,估算结晶温度为750～800℃;7件石墨样品的δ~(13)C值在-19.27‰～-19.90‰,分布非常集中,介于岩浆碳值和有机碳值之间,表明具有两者的混合来源。4件磁黄铁矿样品的δ~(34)S值集中在-2.3‰～-2.9‰之间,接近原始地幔值;在Pb同位素构造环境判别图解上,Pb同位素比值(~(206)Pb/~(204) Pb=18.114～19.040,~(207)Pb/~(204) Pb=15.448 ～ 15.543,~(208) Pb/~(204)Pb=38.253～38.915)显示较好的线性关系,延伸方向与地幔演化曲线的延伸方向基本一致;S-Pb同位素测试结果表明,与石墨共生金属硫化物具有幔源特征。综合黄羊山矿床成矿地质条件、成矿特征、石墨及共生硫化物的物质来源等研究结果,本文初步认为,黄羊山石墨矿床形成于碱性花岗岩的岩浆作用阶段,矿石中的金属硫化物来自岩浆混合作用中的幔源基性端元,碳质由于岩浆同化混染作用达到饱和,在硫化物的催化下沉积形成石墨。  相似文献   

Rb–Sr dating of sulfides and S–Pb isotopic study of the Bayanbaolege Ag polymetallic deposit,Inner Mongolia,NE China     

《Chemie der Erde / Geochemistry》2021,81(1):125724

The large-scale Bayanbaolege Ag polymetallic deposit is situated in the Tuquan–Linxi Fe-Sn-Cu-Pb-Zn-Ag metallogenic sub-belt in eastern slopes of the southern Great Xing’an Range, NE China. The sulfide-quartz vein-type orebodies in the deposit are hosted primarily in the Early Cretaceous granodiorite porphyry and Late Permian strata. Three primary paragenetic stages of veining have been identified: (I) arsenopyrite- pyrite-quartz stage, (II) pyrite-sphalerite-quartz stage, and (III) galena-silver minerals (pyrargyrite, argentite, and pearceite)-calcite stage. The Rb–Sr dating of sulfides yielded an isochron age of 129.9 ± 2.9 Ma (MSWD = 2.1) for the sphalerite, which constrains the mineralization age to the Early Cretaceous. Rb and Sr concentrations in the sulfides ranged from 0.0940 to 1.0294 ppm and 0.0950–3.3818 ppm, respectively. The initial ⁸⁷Sr/⁸⁶Sr value of the sphalerite was 0.70852 ± 0.00018, indicating that the mineralized materials were derived from the mixed crust-mantle source area. S isotope analysis showed that the δ³⁴S values of the sulfide samples varied in a narrow range, from −1.5‰ to +1.3‰ (mean −0.65‰), indicating a magmatic S source. Pb isotopic ratios of the sulfides (²⁰⁶Pb/²⁰⁴Pb = 18.306–18.416, ²⁰⁷Pb/²⁰⁴Pb = 15.524–15.605, ²⁰⁸Pb/²⁰⁴Pb = 38.095–38.479) and the granodiorite porphyry (²⁰⁶Pb/²⁰⁴Pb = 18.341–18.933, ²⁰⁷Pb/²⁰⁴Pb = 15.539–15.600, ²⁰⁸Pb/²⁰⁴Pb = 38.134–38.944) reflect that the ore-forming materials originated from contemporaneous magma with Early Cretaceous granodiorite porphyry. This study of the Bayanbaolege deposit and other hydrothermal deposits in the area provides compelling evidence that the widespread Mesozoic magmatism and mineralization in the southern Great Xing’an Range occurred in an intracontinental extensional tectonic setting, which was associated with the westward subduction of the paleo-Pacific plate.  相似文献   

Geochronology and geochemical properties of the large-scale graphite mineralization associated with the Huangyangshan alkaline pluton,Eastern Junggar,Xinjiang, NW China     

《Chemie der Erde / Geochemistry》2021,81(4):125820

The Huangyangshan alkaline pluton is located within the southern part of the Eastern Junggar orogenic belt in Xinjiang Province, and forms part of the Kalamaili alkaline granite belt. The pluton hosts the Huangyangshan super-large graphite deposit, which develops unique spherical structure and coexists with metal sulfides. This study examines the genetic relationship between the alkaline magmatism that formed the pluton and the graphite mineralization using zircon LA–ICP–MS U–Pb dating, geochemical analysis for representative rock types in the Huangyangshan pluton, and new Re–Os isotope dating for the graphite in the Huangyangshan graphite deposit. Zircons from medium-grained arfvedsonite granite, medium–fine-grained amphibole granite, medium-grained biotite granite, and fine-grained biotite granite phases of the Huangyangshan pluton yield weighted mean U–Pb ages of 322.7 ± 4.5, 318.3 ± 4.0, 303.9 ± 2.1, and 301.1 ± 3.6 Ma, respectively, indicating that all of the granite phases were emplaced during the Late Carboniferous over a period of around 20 Myr. Six graphite samples from the deposit yield a Re–Os isochron age of 332 ± 53 Ma. Combining these ages with the genetic relationship between the graphite mineralization and magmatism in the study area and the relatively large uncertainty on the Re–Os isochron age for the graphite suggests that the mineralization formed at ca. 320 Ma. The graphite samples yield an initial ¹⁸⁷Os/¹⁸⁸Os value of 0.38 ± 0.2, indicative of carbon derived from a mixture of organic and mantle-derived sources. The different granite phases in the Huangyangshan pluton are geochemically similar with relatively high SiO₂ (75.6–78.2 wt%) and Na₂O + K₂O (8.01–9.04 wt%) and relatively low CaO (0.18–0.7 wt%), MgO (0.06%–0.13 wt%) and Fe₂O₃ (T_Fe2O3 = 1.08–2.06 wt%) contents. The granites are enriched in light rare earth elements (LREE), large-ion lithophile elements (LILEs) (e.g. Rb, Th, and K), and high field strength elements (HFSEs) (e.g. Zr and Hf), depleted in heavy rare earth elements (HREEs), and have negative Ba, Sr, P, Ti, and Eu anomalies. These geochemical characteristics are indicative of derivation from juvenile basaltic oceanic crustal materials in the lower crust. This suggests that the Huangyangshan pluton formed from magmas generated by partial melting caused by mantle-derived magma underplating, with the magmas then undergoing mixing, separation, and significant fractional crystallization. Diorite enclaves within the granites have weaker trace element anomalies that are indicative of magma mixing. In addition, the mantle-derived intermediate–basic end-member involved in the magma mixing is likely one of the important carriers of carbon and metal. In summary, the Late Carboniferous Huangyangshan pluton and its associated graphite mineralization formed in a post-collision extensional tectonic setting in the Kalamaili area.  相似文献   

辽宁本溪贾家堡子地区BIF铁矿床地球化学特征     

韩仁萍  寇林林  王筱筝 《地质与资源》2021,30(1):21

利用主量元素和稀土元素相结合的地球化学方法,对本溪贾家堡子铁矿成矿物质来源和矿床成因进行了研究.结果表明：贾家堡子地区条带状铁矿（BIF）的化学成分主要为TFe₂O₃和SiO₂,并且Al₂O₃和TiO₂含量较低,这一特征与鞍本地区及山西五台山和冀东迁安地区条带状铁矿基本一致,指示该条带状铁矿是由极少碎屑物质加入的化学沉积岩.稀土元素呈现弱轻稀土亏损、重稀土富集的特征,具有明显的Eu正异常特征,表明该BIF的稀土元素来源于火山热液和海水的混合液.贾家堡子地区条带状铁矿床成因类型为Algoma型铁矿.  相似文献   

海原-六盘山断裂带现今地震危险性的数值模拟分析     

蒋锋云  季灵运  赵强 《地质力学学报》2021,27(2):230-240

基于正交各向异性理论表征断层的变形行为,将平行断层面的剪切模量和周围介质剪切模量的比值作为反演参数,以海原-六盘山断裂附近现今GPS观测地壳水平运动速度场作为约束,通过构建三维有限元模型,采用遗传算法,反演了海原-六盘山断裂平行断层面的剪切模量分布。结果显示:六盘山断裂中南段平行断层面剪切模量与周围介质接近,且沿断层面地震动活动较为稀疏,反映六盘山断裂两侧近场差异变形较小,和汶川地震前龙门山断裂的情况类似,可能断裂带处于强闭锁状态。整个狭义的海原断裂带平行断层面剪切模量比周围介质要小的多,在0.4以下,且0~5 km要比深部大,可能反映了1920年海原8.5级地震之后,该断裂仍然处于震后调整状态。西段金强河断裂、毛毛山断裂、老虎山断裂浅部0~5 km剪切模量较小,而在5~20 km剪切模量相对较高,结合沿断层面地震活动分布特征,认为金强河、毛毛山断裂浅部可能存在蠕滑,而深部5~20 km存在应变能积累特征,具有强震发生的背景,而老虎山断裂由地表至深部地震活动较为密集,可能存在贯通性蠕滑,强震发生的可能性较小。   相似文献   

电感耦合等离子体发射光谱法和火焰原子吸收光谱法连续测定化探样品中12个元素   总被引：3，自引：3，他引：0  

于阗  张连起  陈小迪 《岩矿测试》2011,30(1):71-74

建立了地质化探样品中不同含量和检出限要求的12个元素的连续测定方法。样品经一次取样,用盐酸-氢氟酸-硝酸-高氯酸溶样,电感耦合等离子体发射光谱法测定铜、铅、锌、钴、镍、镉、锶、钡、钒、锰后,加碘化钾-甲基异丁基甲酮萃取分离,火焰原子吸收光谱法测定银、镉。银、镉的相对标准偏差(RSD,n=12)分别为6.5%、4.7%。与现行分析方法相比,建立的方法灵敏度和精密度高、准确度好,降低了生产成本,缩短了检测时间,尤其适合大量化探样品的测定。  相似文献   

深孔绳索取心安全打捞器的研制与应用          下载免费PDF全文

侯林  刘建福  王建兴  杜绪  饶剑辉 《探矿工程》2011,38(8):41-44

设计了一种可适用于深孔和干孔的绳索打捞、投放内管总成工具。介绍了深孔绳索取心安全打捞器的工作原理及结构组成;对工具内部的机械控制和井下脱卡控制原理进行了研究;介绍了打捞器井下脱卡的具体方法;最后通过野外试验证实了该打捞器可以减少处理事故的时间,性能稳定,拆装、维护方便。  相似文献   

基于等效单自由度体系的结构地震输入能量的研究     

杜敏  林玮  郭晓云 《地震工程与工程振动》2011,31(3):77-82

通过对多自由度体系结构在地震作用下的能量分析,考虑地震动因素和结构自身特性,提出一种框架结构地震总输入能量的简化求解方法.实例计算结果表明:基于等效单自由度体系来估计多自由度体系的地震总输入能,是一种计算简便且较为准确的方法.  相似文献