原状膨胀土剪切力学特性的应变速率效应

为研究应变速率对原状膨胀土力学性状的影响,通过GDS三轴试验系统进行了不同速率和围压下的固结不排水三轴剪切试验,分析了应力−应变曲线、孔隙水压力、剪切强度以及破坏模式随应变速率的变化规律。结果表明：不同应变速率下,膨胀土应力−应变曲线均呈应变硬化型。随着应变速率的增加,不排水剪切强度单调递增,引入应变速率参数ρ_0.9后发现,不排水强度增长率为14.3%～23.2%,平均值为18.4%。低围压下,应变速率对孔隙水压力影响较小,随着围压的增大,孔隙水压力的发展趋势由软化型转变为硬化型,孔隙水压力峰值随应变速率的增大而减小。原状膨胀土应变速率效应与其多裂隙性密切相关,破坏形式表现为小应变速率下主剪切带与次剪切带共存,大应变速率下仅有主剪切带,裂隙或多剪切带的出现强化了膨胀土强度的应变速率效应。     

Quantification of microcrack anisotropy in quartzite — a comparison between experimentally undeformed and deformed samples

In this paper, microcrack patterns in a quartzite are quantified using fractal geometry based methods. Since the quartzite does not show a mesoscopic foliation, the fabric was recognized using anisotropy of magnetic susceptibility (AMS) analysis. Microcracks were investigated in thin sections prepared along the three principal planes of the AMS ellipsoid. Point load tests were performed on cores drilled parallel as well as perpendicular to the magnetic foliation. After experimental deformation, thin sections were prepared in two orientations — (a) parallel to the plane of failure (i.e., parallel to the direction of loading), (b) perpendicular to the plane of failure (i.e., perpendicular to the direction of loading), and microcrack patterns in these sections were investigated. The box-counting method of fractal analysis was first applied to microcracks traced from SEM images from each thin section of the experimentally undeformed as well as deformed samples to establish the fractal nature of the microcrack pattern. It was found that in thin sections perpendicular to the direction of loading, the box (fractal) dimension tends to marginally increase. This is inferred as a manifestation of the increase in complexity of the pattern. The software AMOCADO, which is based on the modified Cantor Dust method of fractal analysis, was applied to microcrack pattern from each thin section in order to quantify the pattern anisotropy. It is noted that the anisotropy significantly reduces in sections perpendicular to the loading direction. SEM data are presented to demonstrate that this reduction in anisotropy is on account of generation and/or growth of new cracks in random orientations. It is envisaged that the approach adopted in this investigation maybe useful in rock mechanics and mineral-resource applications in future.     

坡沟系统坡面径流流态及水力学参数特征研究

利用变坡度坡沟系统概化模型和人工模拟降雨试验,定量分析了在60、90和130mm/h降雨强度下坡沟系统坡面径流流态及水力学参数特征。结果表明,上方汇水和降雨强度的增大使坡沟系统水流雷诺数和弗劳德数呈明显增大,水流流态由缓流演变为急流,坡面水流阻力系数明显减小,从而使坡沟侵蚀产沙量显著增大。     

Grain-size spectra maps of beaches in W. Peloponnese, Greece

Grain-size spectra maps of sands from beaches of the western Peloponnese are related to statistical parameters and can be used to infer characteristics of the sedimentation process involved which were unresolved by previous statistical analysis. On the basis of similarities in spectral patterns, the studied beaches fall into four groups: A, B, C, and D. The periodicity observed on the sinuous pattern of the spectra map of groups A and B is interpreted as indicating edge-wave activity. Regarding group D, the gradual W—E increase of particle size along the coast suggests a W—E increase of wave energy, which is also reflected by the inclined trend of the spectra map. Lack of periodicity on the contour pattern of group C probably reflects intensive sample-to-sample sorting variation.     

干旱区绿洲灌溉条件下生态服务价值研究——以新疆轮台县为例

基于RS、GIS、景观生态学等方法,以新疆典型干旱区轮台县为研究区,利用1997年、2007年、2017年三期遥感影像解译结果,定量分析轮台县20年间土地利用景观格局变化特征,并运用生态系统服务价值（ESV）估算原理,定量分析轮台县生态服务功能ESV的年际变化,探讨ESV在景观格局演变下的损益和响应,来反映生态输水对塔河沿岸生态的影响。结果表明：轮台县以未利用地大幅度减少,林地与草地的大量增加为主,同时耕地、水域、建设用地以及冰川的面积也有不同程度的增加,但相对于整个县域面积依然相对较小;各斑块类型景观格局指数和整体景观格局指数以及空间格局都发生了不同程度的变化,未利用地对景观整体的控制性减弱,土地利用均匀性和多样性增加,最大斑块指数变化显著,散布并列指数先略有下降后明显增加;轮台县20年间各项生态系统服务功能的ESV均呈显著增加的趋势,ESV总量不断增大;轮台县ESV的增益集中在林地的增加上,占总增益的65.9%,轮台县ESV的损益集中在建设用地和未利用地的转入上,说明林地的增加和未利用地的减少是轮台县ESV增加的主要原因。该研究体现典型水源灌溉对轮台县生态的影响,为干旱区生态系统改善和土地利用规划提供依据。     

艾比湖绿洲实际蒸散量变化特征及与景观格局的关系

基于Budyko曲线方程计算新疆艾比湖绿洲1960—2013年实际蒸散量的年际和季节变化特征,选取研究区四期遥感影像进行土地利用/覆被分类,使用Fragstas 4.2软件计算景观格局指数,并分析实际蒸散量与景观格局指数之间的关系。结果表明：艾比湖绿洲实际蒸散量多年平均值为162.97 mm,并呈上升趋势,变化速率为7.76 mm·（10a）^-1;夏季和秋季的实际蒸散量为上升趋势,春季则呈下降趋势;年实际蒸散量在1987年发生突变性增加,夏季和秋季实际蒸散量的突变年份分别为1992年和1975年,春季不存在突变点,这与降水量的突变状况一致,说明降水量的变化对实际蒸散量的变化有很大影响。四期土地利用/覆被图中荒漠占主导地位,耕地和城镇用地增长较为明显,分别增长了409.69%和704.56%。斑块类型级别上,不同地类的景观格局指数差异明显;景观级别上,各景观格局指数均为波动增加趋势。斑块类型级别上,仅有水域斑块数量NP和斑块密度PD与实际蒸散量呈显著负相关;景观级别上,实际蒸散量与最大斑块指数LPI、蔓延度指数CONTAG及景观连通性指数COHESION呈负相关,与斑块数量NP、斑块密度PD等指数呈正相关。实际蒸散量与聚集度指数AI的相关性最高,达到0.953（P<0.05）;与NP和PD的相关性最低,仅为0.148。因此,AI指数在艾比湖绿洲可以较好地表征实际蒸散量的变化。     

藻类生物化学成分差异对其热解生烃产率和特征的影响

藻类生物化学成分差异对其热解生烃产率和特征的影响吴庆余，章冰，盛国英，傅家谟（南京大学生物科学与技术系．南京２１００９３）（中国科学院广州地球化学研究所．广州５１０６４０）关键词藻类热模拟成烃，生物化学降解，有机地球化学浮游藻类生物的热降解模拟实验和...     

Element partitioning between olivine and silicate melt under high pressure

Element partitioning between olivine and silicate melt has been investigated at pressures 1–14 GPa, by using a 6–8 type multi-anvil high pressure apparatus. In order to observe systematics in the partitioning of trivalent ions, Li was added to the starting materials in order to increase the concentration of trivalent ions in olivine. With increasing pressure, it was found that partition coefficients of most of the elements gradually decreased. Trivalent ions generally showed parabolic pattern on partition coefficient — ionic radius diagram. When pyrolite-like material was used as the starting material, partition coefficient of Al, D_Al, gradually increased with increase in pressure while the partition coefficients of the other elements decreased, and the D_Al deviated from the parabolic pattern of other trivalent ions. The deviation of D_Al from the D pattern of the other trivalent ions was also found when olivine was employed as main component of the starting material. This result may be ascribed to the compositional change of coexisting silicate melt with increase in pressure.     

青藏高原木里矿区及其周边土地覆被变化及景观格局脆弱性响应

矿区开发会导致周边土地覆被及景观格局发生剧烈变化, 但目前对青藏高原典型矿区及其周边土地覆被长时间序列变化缺乏动态监测, 尤其缺乏对景观格局脆弱性响应特征的深入认识, 因此无法针对矿区合理开发和生态修复等提出有效的科学指导。通过遥感技术和土地变化科学研究手段, 以及景观格局脆弱性概念, 对青藏高原北部木里矿区及周边1975 - 2016年土地覆被时空变化和景观格局脆弱性进行分析和评估。结果表明： 木里矿区在2000年后剧烈扩张, 导致周边土地覆被面积缩减, 其中高寒草甸湿地面积损失最大, 其次为其他和高寒草甸。矿区开发对周边生态系统的间接影响效应在逐渐增大, 表现为水域面积减少, 高寒草甸湿地出现退化以及矿区发生少量逆转。受矿区扩张影响, 区域景观格局脆弱性不断增强, 可能对周边生态系统服务功能产生负面影响。因此, 未来矿区的生态修复和规划过程中, 应当优化景观格局, 降低景观格局脆弱性。研究成果可为青藏高原及其他生态脆弱地区的矿区合理开发规划及生态修复等工程提供一定参考。     

断裂带土壤气测量方法在断层活动性研究中的应用——以嘉峪关断层为例

为了判断甘肃省嘉峪关断层监测点气氡浓度2015年6月以来的高值异常变化是否反映了嘉峪关断层活动的增强,本文基于土壤气跨断层分布规律,应用跨断层测量方法,通过多组分相关性分析及理论建模,综合分析了嘉峪关断层监测点气氡浓度高值异常变化与断层活动的关系。结果显示：监测点断层气中氡浓度快速增加期间,CO₂、CH₄和H₂的浓度没有增加,气氡与CO₂、CH₄浓度的变化不具正相关关系,表明监测点增加的氡气来源深部较浅,不代表断层活动的增强。监测点两侧跨断层测量结果表明,地表环境未改变一侧的氡气浓度符合断层气分布规律,地表环境发生改变一侧的氡气浓度不符合断层气分布规律,并且地表环境的改变时间与监测点气氡浓度异常变化时间同步。因此监测点气氡浓度的高值异常是由地表环境的改变引起的,嘉峪关断层的活动并没有增强。该方法为用断裂带土壤气体测量方法研究断层活动性的可靠性提供了思路。     

Late-Pleistocene and Holocene remains of Hysterocarpus traski (Tule Perch) from Clear Lake,California, and inferred Holocene temperature fluctuations

The remains of scales of Hysterocarpus traski Gibbons (Tule perch) were found throughout a 27.44-m core from Clear Lake. Most scales occurred between the mud surface and deposits approximately 11,000 years old. Changes in growth rates of the animals were examined by measuring scale annuli and applying an empirically established regression of fish length on scale radius. The data indicate a pattern of accelerating growth rates, reaching a peak between ?4000 and 2800 BP. After ?2800 BP, growth rates decline markedly. Because the growth rates of these animals are essentially dependent on temperature, the changes observed in the patterns of growth probably reflect changes in climate in the northern Coast Range. The general pattern of inferred temperature increase during the early and middle Holocene, ending between ?4000 and 2800 BP, is consistent with evidence from tree-line studies and palynology indicating higher temperatures in parts of the western United States during this period.     

甘肃省定西市水源地地下水资源分析评价

在分析定西市城区主要供水水源地内官-香泉盆地水文地质条件的基础上,对盆地地下水位历年变化规律进行了分析。分析表明：地下水位历年呈持续下降趋势,汛期7～9月降水补给地下水资源量增加,地下水位持续回升;5月、6月农业灌溉用水量加大,地下水位下降速率加大。通过地下水资源均衡计算,盆地地下水处于负均衡状态。并对引洮供水工程引水灌溉后的地下水动态作了趋势预测。     

黄土高原中部7～2Ma期间古植被变化的分子化石证据——以赵家川剖面为例

植物叶蜡正构烷烃组分能够在地质体中长久保存,并记录历史时期植被变化的信息。本研究通过对黄土高原中部董志塬西峰地区赵家川剖面古土壤中正构烷烃组分的分析,讨论7～2Ma期间黄土高原植被变化的植物叶蜡组分变化特征及其对气候变化的响应。结果表明:从7.0Ma至3.4Ma,正构烷烃C31/C27和C31/C29比值处于相对低值的波动范围,范围分别为0.5～1.9和0.6～1.3,表明该时期以木本植物占优势的生态格局;在3.4Ma前后,古土壤中保存的古植被叶蜡正构烷烃组分的C31/C27和C31/C29比值有一个明显的增加,分别从0.8变化到2.9,从0.7变化至1.6,即古生态系统中草本植物的相对比例突然增加;从3.4Ma至2.0Ma,正构烷烃C31/C27和C31/C29比值处于相对高值的波动范围,范围分别为1.7～3.3和1.1～1.6,指示该时期木本植物减少,草本植物增加的生态格局。我们推测这个生态系统的变化可能响应晚新生代3.5Ma左右的中国内陆干旱化,并形成了自此以后黄土高原塬面以草原或森林草原为主的自然生态格局。     

土地利用变化对海河流域典型区域的径流影响

为研究海河流域径流对土地利用变化的响应,以阜平流域、匡门口流域和界河铺流域为研究区,利用1970—2011年的水文气象资料,分析了不同土地利用的时空转移特征,然后结合SWAT(Soil and Water Assessment Tool)模型,设置4种土地利用情景,评价了土地利用变化对径流的影响。结果表明:模型能够较好地模拟全年及汛期月流量过程;多年径流量呈下降趋势,20世纪80年代到90年代中期呈波动性变化;不同的土地利用类型在时空上的转化呈现可逆性,主要是林地增加,草地减少,耕地略有增加;林地的增加和草地的减少会降低汛期径流量以及最大月径流量;汛期径流系数随着林地面积的增加而减小。合理地规划土地利用格局,对控制流域水文事件具有重要意义。     

高度城镇化背景下珠三角地区极端降雨时空演变特征

为分析城镇化发展程度与极端降雨变化之间的关系,选取珠江三角洲地区22个雨量站1973—2012年的小时降雨资料,利用空间分析、线性回归、滑动平均和Mann-Kendall趋势检验等方法,分析高度城镇化背景下珠三角地区极端降雨时空分布规律和变化特性,并解析暴雨雨型变化特征。结果表明:①珠江三角洲高度城镇化地区极端降雨量上升了44.3 mm/（10 a）,呈显著增加趋势,相邻其他地区则无明显变化,高度城镇化地区的前汛期极端降雨量显著增多是造成其年极端降雨量增加的主要原因。②珠三角地区暴雨雨型以单峰型为主,其中以雨峰在前的Ⅰ型暴雨占比最高,约为33.7%,高度城镇化地区Ⅰ型暴雨发生频率明显增加,易导致暴雨内涝事件增加,需加强高度城镇化地区防洪排涝工作。     

Discrete Element Modeling of a Subduction Zone with a Seafloor Irregularity and its Impact on the Seismic Cycle

Seafloor irregularities influence rupture behavior along the subducting slab and in the overriding plate, thus affecting earthquake cycles. Whether seafloor irregularities increase the likelihood of large earthquakes in a subduction zone remains contested, partially due to focus put either on fault development or on rupture pattern. Here, we simulate a subducting slab with a seafloor irregularity and the resulting deformation pattern of the overriding plate using the discrete element method. Our simulations illustrate the rupture along three major fault systems: megathrust, splay and backthrust faults. Our results show different rupture dimensions of earthquake events varying from tens to ca. 140 km. Our results suggest that the recurrence interval of megathrust events with rupture length of ca. 100 km is ca. 140 years, which is overall comparable to the paleoseismic records at the Mentawai area of the Sumatran zone. We further propose the coseismic slip amounts decrease and interseismic slip amounts increase from the surface downwards gradually.     

近15a乌鲁木齐市城市用地扩展动态及其空间特征研究

以乌鲁木齐市为例,在遥感和GIS技术的支持下,对干旱区城市土地利用结构、空间格局动态变化与城市扩展的空间特征进行定量分析.采用1987年、2002年两期陆地卫星影像为基础数据源,提取了研究时段内乌鲁木齐城市土地利用变化信息;结合景观生态学原理和方法,对研究区城市景观的动态变化进行定量分析.并引入建成区空间密度作为定量指标,分析总结了乌鲁木齐市扩展变化的空间特征.结果表明,1987-2002年间乌鲁木齐城市土地利用状况发生了较大的变化:城市建成区和绿地面积增长,水体面积减少;景观斑块分离度增强,边界构成曲折化,整体格局趋于复杂;在空间上,城市扩展主要沿西、西北及东北3个主要方向进行,并形成了建成区密度由内而外递减的空间分异特征.     

Analyzing the effects of historical and recent floods on channel pattern and the environment in the Lower Omo basin of Ethiopia using satellite images and GIS

Previous accounts and recent observations indicate that the pattern and geometry of the Omo River meanders in the Lower Omo basin of Ethiopia had already been established in earlier times by large floods that took place after extended periods of drought. The cross-sectional changes resulted from floods in the nineteenth and twentieth centuries, were then simply limited to small degree channel widening and entrenchment, and floodplain erosion and deposition. The effects of the August 2006 flood, although widespread and destructive for the environment, were also modest as far as adjusting the channel pattern is concerned. Changes in channel profiles at short-term scales usually come in the form of aggradation and degradation. Interpretations of satellite images taken before and after the flood showed the accumulation of coarse sediments in the channel. There are also some sporadic indications for an increase in channel width. Widening in response to high amount of discharges can generally be expected during floods. Besides, signs of channel shortening were observed in some places. Apart from these minor changes, the dimension of meandering segments or the outline of the entire meander belt, and the basic morphology of the channel remained unaffected.     

Latitude matters: an examination of behavioural plasticity in dietary traits amongst extant and Pleistocene Rangifer tarandus

The geographical distribution of species affects their dietary traits relative to resources available in different latitudes. Dietary traits of Rangifer tarandus, a species with a wide geographical distribution, were investigated using tooth mesowear and microwear methods in eight extant populations from Canada. The data show a latitudinal shift corresponding to a vegetational gradient from the taiga to the tundra, i.e. an increase of lichen consumption from the low to the high latitudes. This pattern is also evidenced in the Pleistocene fossil record of Europe where R. tarandus populations from low latitude localities show a lower consumption of lichen than at higher latitudes.