Quantitative relationship between surface sedimentary diatoms and water depth in North-Central Bohai Bay,China

To study the quantitative relationship between surface sedimentary diatoms and water depth, 67 surface samples were collected for diatom analysis on eight profiles with water depth variation from the muddy intertidal zone to the shallow sea area in North-Central Bohai Bay, China. The results showed that the distribution of diatoms changed significantly in response to the change in water depth. Furthermore, the quantitative relationship between the distribution of dominant diatom species, their a...     

从浅表花岗岩体中地应力测试深度与应力值间关系分析剥蚀厚度

针对浅表高水平地应力和高侧压系数常出现在岩浆岩和变质岩中的现象,以广泛分布的形成于地下深处的花岗岩为例,指出构造隆升作用下,花岗岩从形成时位于深部到现在处于剥蚀卸荷过程中而常出露地表,无论是采用静水压力还是弹性体假设,都可得出其侧压系数明显变大的结论。对254组花岗岩地应力现场实测结果统计,得到了侧压系数拟合公式更符合花岗岩实测结果分布情况。由广义虎克定律出发,结合垂向卸荷后地下某处水平应变为0的假设,推导出花岗岩体剥蚀厚度计算公式,其结果接近目前为止认识到的剥蚀厚度的上限值。初步工程资料分析对比发现,大亚湾燕山期花岗岩地质分析剥蚀厚度为1 300 m,计算结果介于1 500～3 000 m之间;三峡工程船闸区花岗岩剥蚀厚度为1 700～3 200 m,与裂变径迹法测试结果比较吻合。结果说明,花岗岩体剥蚀厚度相对于现在一般工程埋深是比较大的     

煤炭地震激发介质与井深的关系

通过地震波在近地表附近双源传递机理的研究,论述了近地表介质与激发井深的关系,研究了利用地震波最大激发能量与地震波最大信噪比选择爆破源地震激发井深的方法。三维地震实例研究结果表明,地震波在近地表附近的双源传递与品质因数是选择地震波的激发井深的重要因素。从实例结果来看,该方法不仅取得了高质量的勘探成果,而且节约了采集费用。     

深埋砂层旁压特征参数的深度效应研究

深埋砂层作为一种散粒结构体系,其原状力学特性的准确测定是岩土工程中的难点问题,旁压试验是一种理想的深层原位测试方法,但在深度效应上缺乏定量评价标准。为解决旁压试验深度效应问题,采用自主研制的物理模型试验系统,模拟深埋砂层的受力状态,通过施加不同的上覆压力 模拟不同深度下的旁压试验,获得了旁压测试指标旁压模量EM、临塑压力Pf与上覆压力 之间的关系,提出了采用临塑压力Pf确定地基承载力特征值fak的修正方法。试验结果表明：旁压试验确实存在深度效应,随着试验深度的增大,上覆压力 相继增大,但旁压模量EM的变化并不明显,临塑压力Pf与上覆压力 呈线性相关关系。为深埋砂层物理力学性质的确定提供参考和依据。     

干旱、半干旱地区蒙古扁桃种子萌发对土壤水分和播种深度的响应特征

蒙古扁桃种子在4%~16%的各含水量条件下, 出苗率高达96%~98%且差异不显著(P>0.05), 在4%~13%的土壤含水量下, 发芽指数、活力指数、平均出苗日数极显著高于16%含水量下的值(P<0.01), 其种子萌发最适宜的土壤含水量为4%~13%. 随土壤含水量的升高, 苗高增加, 根冠比和壮苗指数降低, 根长、幼苗生长量、干物质积累量先升高后降低, 幼苗生长最适宜的土壤含水量为7%~16%; 较低的土壤水分下可以提高幼苗的抗旱性, 有利于培育壮苗. 随播种深度的增加, 出苗率下降, 平均出苗日数增加, 出苗速率放缓, 保证全苗的最适宜播深为0~1 cm, 保证壮苗的最适宜播深为1~3 cm. 种子萌发形成的幼苗为子叶留土型双子叶植物幼苗.     

Prograde pressure–temperature paths in the pelitic schists of the Sambagawa metamorphic belt, SW Japan

Prograde P–T paths recorded by the chemistry of minerals of subduction‐related metamorphic rocks allow inference of tectonic processes at convergent margins. This paper elucidates the changing P–T conditions during garnet growth in pelitic schists of the Sambagawa metamorphic belt, which is a subduction related metamorphic belt in the south‐western part of Japan. Three types of chemical zoning patterns were observed in garnet: Ca‐rich normal zoning, Ca‐poor normal zoning and intrasectoral zoning. Petrological studies indicate that normally‐zoned garnet grains grew keeping surface chemical equilibrium with the matrix, in the stable mineral assemblage of garnet + muscovite + chlorite + plagioclase + paragonite + epidote + quartz ± biotite. Pressure and temperature histories were inversely calculated from the normally‐zoned garnet in this assemblage, applying the differential thermodynamic method (Gibbs' method) with the latest available thermodynamic data set for minerals. The deduced P–T paths indicate slight increase of temperature with increasing pressure throughout garnet growth, having an average dP/dT of 0.4–0.5 GPa/100 °C. Garnet started growing at around 470 °C and 0.6 GPa to achieve the thermal and baric peak condition near the rim (520 °C, 0.9 GPa). The high‐temperature condition at relatively low pressure (for subduction related metamorphism) suggests that heating occurred before or simultaneously with subduction.     

1979-2014年东北地区雪深时空变化与大气环流的关系

基于被动微波遥感反演的雪深数据集（1979-2014年）,利用Mann-Kendall检验、R/S分析、相关分析和小波分析等方法研究了东北地区雪深时空变化特征及其与大气环流的关系。结果表明：1979-2014年,东北地区年均雪深总体呈减小趋势,减小速率为-0.084 cm·（10a）^-1。其中,春季雪深减小速率最大,为-0.19 cm·（10a）^-1（P<0.05）,其次是冬季[-0.17 cm·（10a）^-1],而秋季雪深减小速率最小,仅为-0.05 cm·（10a）^-1。空间上,平原区（东北平原和三江平原）与少部分高原区（呼伦贝尔高原西南部）年均雪深呈增大趋势,山地（大、小兴安岭和长白山）与高原大部（内蒙古高原）雪深呈减小趋势,而且雪深增大区域的面积和变化速率均小于雪深减小的地区。东北地区年均雪深变化的Hurst指数为0.85,表明雪深未来减小的持续性很强;同时雪深变化具有22 a的主周期。春秋季雪深变化与东亚槽强度及北半球极涡面积呈显著负相关性,而冬季雪深与北半球副高强度关系密切。     

湿陷性黄土场地湿陷下限深度与桩基中性点位置关系研究

湿陷性黄土场地的湿陷下限深度与桩基中性点位置密切相关,为了解决桩基设计方案不当问题,如何准确判定湿陷下限深度显得十分重要。在系统分析并总结宁夏固原桩基系列浸水试验、兰州和平镇黄土浸水试验及其他地区桩基浸水试验研究成果的基础上,揭示了黄土湿陷下限深度与桩基中性点位置确定的相互关系,得出了以下研究成果：（1）指出了均质黄土现场浸水试验水的竖向渗透深度是有限的（一般为20～25 m）,现场黄土湿陷发生的下限深度也是有限的,不宜按室内试验的湿陷系数确定的下限深度来直接评判;（2）给出了室内湿陷性评价试验中湿陷系数 或自重湿陷系数 随地区和深度变化的取值建议,同时,建议在湿陷量计算时引入深度修正系数和地基土浸水机率系数,初步给出大厚度湿陷性黄土场地不同地区湿陷下限深度评价系数 ,可以有效减小湿陷性评价的室内外差异;（3）由室内试验计算确定的湿陷下限深度偏于保守,导致桩基设计过分夸大了负摩阻力的不利作用,造成桩基设计承载力偏低;（4）大厚度湿陷性黄土场地桩的中性点最深位置不宜大于20～25 m,湿陷性评价下限深度小于20 m的场地,宜按评价深度确定中性点位置;给出了桩侧负摩阻力估算方法,并建议桩基负摩阻力平均值取20～35 kPa为宜。     

Early Tertiary fluid flow and pressure–temperature conditions in the Shimanto accretionary complex of south-west Japan: constraints from fluid inclusions

The pressure and temperature history of the Tertiary Shimanto belt of south-west Japan has been elucidated by analysing fluids trapped in quartz crystals which grew syn-kinematically along late-stage brittle faults. The samples come from three areas that span the Paleogene exposures on the Muroto Peninsula of Shikoku Island. Applying microthermometric and laser Raman microsampling techniques to coeval water-rich and carbonic fluid inclusions, we have constrained the pressure and temperature conditions that accompanied a widespread and kinematically distinct phase of deformation. The results suggest elevated geothermal gradients during late-stage deformation, conditions that are in disaccord with previous plate reconstructions that have depicted old, thermally mature Pacific crust subducting beneath Eurasia during the early to middle Tertiary. These conditions can most easily be accounted for by including an additional plate boundary in the western Pacific during Paleogene time. Plate reconstructions that include the Kula plate in this region are therefore consistent with our findings. In addition, our results provide clues to the conditions that likely accompany seismogenic deformation at active convergent plate boundaries.     

青藏高原多年冻土区地温年变化深度的变化规律及影响因素

地温年变化深度的准确判断对于多年冻土发育特征评估、寒区冻土模式下边界深度的确定具有重要意义.通过对青藏高原地区典型钻孔地温数据进行分析,初步揭示了多年冻土地温年变化深度的变化规律及其影响因素,并提出一种简化了地表和活动层状态影响的地温年变化深度估算方法.结果表明：研究区低温冻土的地温年变化深度平均值比高温冻土大4.6 m,随着冻土温度升高,地温年变化深度基本上呈减小趋势,部分低温冻土钻孔由于土层含水率过高导致地温年变化深度相对较小;由于活动层水热动态和冻融过程的影响,地温年变化深度与浅层（0.5 m）温度年较差相关性不显著,而与多年冻土上限附近温度年较差的大小呈显著正相关关系;地层介质的热扩散率差异是导致地温年变化深度区域差异和变化的主要原因,土层含水率、温度、质地以及水的相态是影响地层热物理性质重要因素.     

西北太平洋热带气旋风压关系的变异分析

利用1949 ～2008年共60年的热带气旋(TC)历史资料,分析TC中心最低气压和平均最大风速的相互关系,发现存在阶段性特征变异,继而对其进行了定量分析,得出过去60年中国整编的历史热带气旋资料中,风压关系序列前后明显不一致,存在变异现象,其变异点有两个,即1971/1972年、1974/1975年,其中以前者最为明...     

基于埋深变化的川南龙马溪组页岩孔隙特征及控制因素分析

[研究目的]中国浅层-中深层页岩气勘探开发技术已经趋于成熟,深层页岩成为下一步勘探开发的重点,探明不同埋深条件下页岩的孔隙特征及其控制因素利于推动深层页岩的评优选区工作.[研究方法]本文基于核磁共振、场发射扫描电镜和X-射线衍射等实验分析手段,对比性评价了川南地区不同深度的龙马溪组页岩孔隙度、孔隙结构参数特征并进行影响...     

Dating of raised marine and lacustrine deposits in east Greenland using beryllium‐10 depth profiles and implications for estimates of subglacial erosion

Here we combine ¹⁰Be depth profile techniques applied to late glacial ice‐contact marine and lacustrine deltas, as well as boulder exposure dating of associated features in the Scoresby Sound region, east Greenland, to determine both the surface age and the magnitude of cosmogenic nuclide inheritance. Boulder ages from an ice‐contact delta in northern Scoresby Sund show scatter typical of polar regions and yield an average age of 12.8 ± 0.5 ka – about 2 ka older than both our average profile surface age of 10.9 ± 0.7 ka from three depth profiles and a radiocarbon‐based estimate. On the other hand, boulder exposure ages from a set of moraines in southern Scoresby Sund show excellent internal consistency for polar regions and yield an average age of 11.6 ± 0.2 ka. The profile surface age from a corresponding ice‐contact delta is 8.1 ± 0.9 ka, while a second delta yields an age of 10.0 ± 0.4 ka. Measured ¹⁰Be inheritance concentrations from all depth profiles are internally consistent and are between 10% and 20% of the surface concentrations, suggesting a regional cosmogenic inheritance signal for the Scoresby Sound landscape. Based on the profile inheritance concentrations, we explore the first‐order catchment‐averaged bedrock erosion under the Greenland ice sheet, yielding estimates of total erosion during the last glacial cycle of the order of 2–30 m. Copyright © 2010 John Wiley & Sons, Ltd.     

Responses of phreatophyte transpiration to falling water table in hyper-arid and arid regions,Northwest China

Quantitative assessment of the impact of groundwater depletion on phreatophytes in (hyper-) arid regions is key to sustainable groundwater management. However, a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking. A variable saturated flow model, HYDRUS-1D, was used to numerically assess the influences of depth to the water table (DWT) and mean annual precipitation (MAP) on transpiration of groundwater-dependent vegetation in (hyper-) arid regions of northwest China. An exponential relationship is found for the normalized transpiration (a ratio of transpiration at a certain DWT to transpiration at 1 m depth, T_a*) with increasing DWT, while a positive linear relationship is identified between T_a* and annual precipitation. Sensitivity analysis shows that the model is insensitive to parameters, such as saturated soil hydraulic conductivity and water stress parameters, indicated by an insignificant variation (less than 20% in most cases) under ± 50% changes of these parameters. Based on these two relationships, a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for (hyper-) arid regions using MAP only. The estimated T_a* from the model is reasonable by comparing with published measured values.© 2021 China Geology Editorial Office.     

水压致裂煤层裂缝发育特点的研究

本文对煤岩基本力学性质、煤层水压致裂缝形成条件、裂缝形态以及裂缝开裂角方位等基本理论进行了研究与探讨，通过大量煤岩力学性质测试，证实了试验区目的层煤岩弹性模量低，泊松比较高，脆性大，易破碎，易压缩。文章还得出了目的层煤岩Ｍｏｈｒ断裂准则二次抛物线型包络线，煤层水压致裂裂缝形式判断，裂缝开裂角方位的计算公式以及有关结论。     

Application of K-feldspar–jadeite–quartz barometry to eclogite facies metagranites and metapelites in the Sesia Lanzo Zone (Western Alps, Italy)*

The eclogite facies assemblage K-feldspar–jadeite–quartz in metagranites and metapelites from the Sesia-Lanzo Zone (Western Alps, Italy) records the equilibration pressure by dilution of the reaction jadeite+quartz=albite. The metapelites show partial transformation from a pre-Alpine assemblage of garnet (Alm₆₃Prp₂₆Grs₁₀)–K-feldspar–plagioclase–biotite±sillimanite to the Eo-Alpine high-pressure assemblage garnet (Alm₅₀Prp₁₄Grs₃₅)–jadeite (Jd_80–97Di_0–4Hd_0–8Acm_0–7)–zoisite–phengite. Plagioclase is replaced by jadeite–zoisite–kyanite–K-feldspar–quartz, and biotite is replaced by garnet–phengite or omphacite–kyanite–phengite. Equilibrium was attained only in local domains in the metapelites and therefore the K-feldspar–jadeite–quartz (KJQ) barometer was applied only to the plagioclase pseudomorphs and K-feldspar domains. The albite content of K-feldspar ranges from 4 to 11 mol% in less equilibrated assemblages from Val Savenca and from 4 to 7 mol% in the partially equilibrated samples from Monte Mucrone and the equilibrated samples from Montestrutto and Tavagnasco. Thermodynamic calculations on the stability of the assemblage K-feldspar–jadeite–quartz using available mixing data for K-feldspar and pyroxene indicate pressures of 15–21 kbar (±1.6–1.9 kbar) at 550±50 °C. This barometer yields direct pressure estimates in high-pressure rocks where pressures are seldom otherwise fixed, although it is sensitive to analytical precision and the choice of thermodynamic mixing model for K-feldspar. Moreover, the KJQ barometer is independent of the ratio PH2O/P_T. The inferred limiting a(H₂O) for the assemblage jadeite–kyanite in the metapelites from Val Savenca is low and varies from 0.2 to 0.6.     

气象要素影响下雪冰离子淋溶过程研究——以乌鲁木齐河源1号冰川为例

为了更好地理解化学离子在雪坑中的迁移和保存,进一步解释冰芯记录,基于乌鲁木齐河源1号冰川海拔4130 m处的雪冰化学资料,研究了气温和降水与离子淋溶过程的关系.结果表明：气温与离子浓度呈负相关关系,夏季的雪坑离子浓度波动剧烈,冬季的雪坑离子浓度相对稳定.离子浓度随正积温的升高呈指数衰减趋势,当正积温至0℃以上时,离子浓度急剧降低;当正积温升至60℃左右时,离子浓度呈缓慢降低.不同离子的淋溶过程对正积温的响应有所不同,随着正积温的增加,SO₄^2-,NO₃^-,Na⁺,Cl^-,NH₄⁺和Ca²⁺的衰减趋势非常显著,而Mg²⁺和K⁺则呈现无规律性的变化.淋溶因子指出,融水渗浸作用导致雪坑中大部分离子被淋溶;不同离子的淋溶因子也有明显差异,Mg²⁺淋溶因子最小（0.43）,SO₄^2-淋溶因子最大（0.84）,说明Mg²⁺最为稳定,而SO₄^2-最易淋溶.降水对雪坑离子浓度的影响较为微弱,主要通过增加表层雪离子浓度而提升整个雪坑的离子浓度.     

沿海下卧软弱夹层碎石回填地基15000kN·m高能级强夯试验

针对某沿海下卧软弱夹层的碎石回填土地基,在国内首次开展了15000kN·m高能级强夯的现场试验。通过单点夯试验各夯点与夯坑周围地面沉降观测及强夯前后地基动力触探测试结果的对比分析,揭示了下卧软弱夹层的碎石回填地基上15000kN·m高能级强夯的作用机制,得出该条件下强夯的有效加固深度为11.5m,主夯点间距宜为12.5m,夯击数宜为18～22击的有关结论。其结果可为类似工程参考。