Hydraulic conductivity of shallow sandy aquifers: Effects of sedimentologic and diagenetic differences

The relationship between values of hydraulic conductivity determined from grain-size methods,K _gr, and those from pumping-test methods,K _pt, have been evaluated statistically using data from recent and older sandy materials. It is shown that both methods generally give the same values only in recent sediments that have not been subjected to significant diagenetic alteration and give variable results in older and diagenetically altered sediments. The ratioK _pt/K_gr appears to vary, probably in response to the degree of diagenetic alteration. It is further found that methods incorporating the effects of grain size (d1O or d50) and sorting could give betterK values than those incorporating the effect of grain-size only and, thus, suggest the joint inclusion of both parameters in the grain-size determination of permeability.     

南宁、百色盆地红土风化壳的地球化学特征及其环境意义

本文以广西南宁盆地那桐风化壳，及百色盆地江泽风地壳的大量土体化学分析数据为依据，进行了第四纪红土的确认、形成、分布和土壤肥力状况．以及通过地球化学强度、硅铁系数、硅铝系数等指标进行了两风化壳的对比研究。同时，还探讨了风化壳的发育过程及其与环境的关系。     

试论我国历史文化名城的类型及其特征

本文论述了历史文化名城的涵义,指出我国历史文化名城的空间分布特征,阐述划分名城类型的方法。运用比值法,将我国99座历史文化名城分成六大类型,分析每一类型的主要特征,对城市建设和旅游业的发展提出建议。     

A stochastic distributed model of soil erosion by overland flow

A model has been built to simulate runoff and erosion on slopes of varying form with soil of varying hydraulic conductivity, porosity, storage capacity, and particle size distribution. The model is based on known physical laws and takes into account spatially dependent random variation in the initial conditions of the soil. The rainfall is similarly both random and autocorrelated in space. Detailed results show how runoff is generated as a result of slow conductivity and high water table, how this leads to erosion, the degradation of the land surface, the capture of flow lines, and the development of networks of rills. The last accords well with results from laboratory experiments. Changing the initial conditions produces results that accord with intuition and reality.     

An appraisal of the velocity-reversal hypothesis for stable pool-riffle sequences in the river severn,England

The ‘velocity-reversal hypothesis’ is the linchpin for a number of recent conceptual models pertaining to sediment sorting and the maintenance of pool-riffle sequences in gravel-bedded streams. The literature in support of the hypothesis together with published adverse criticism is reviewed. It is concluded that convincing evidence for the ubiquitous occurrence of such a reversal in a range of channel geometries is currently unavailable. Continuity considerations indicate that riffles need to be considerably wider than pools for a reversal in the mean velocity to occur under conditions of subcritical flow, high stage, and stable morphology. These observations are substantiated by a detailed study of the hydraulic geometry of stable pool-riffle sequences in the River Severn, England. Neither the sectionally-averaged velocity nor the near-bed shear velocity is sensibly greater in the pools than over the riffles during bankfull or near bankfull flow. Instead a tendency towards equalization of the values of average hydraulic variables is noted as discharge increases. A detailed investigation of the three-dimensional character of the flow is required to demonstrate whether the entrainment forces within pools can locally exceed those over neighbouring riffles. Unusual behaviour of the energy gradient over riffles during moderate discharges is related to backwater effects as mediated by the spacing of the riffles. The hydraulic data are used to comment on the stability of the test reaches in the context of the development of the River Severn in the vicinity of Shrewsbury.     

围压条件下岩石的抗拉强度

用水压致裂法对7种岩石的厚壁圆筒试件进行不同围压下的抗拉强度实验,并从试件致裂瞬间的内壁环向应力σt,环向应变εt等五种参数随围压变化的角度,对围压条件下岩石的抗拉强度进行研究。结果表明,若用σt表示岩石的应力抗拉强度,则σt随围压的增加而减少,并由低围压时的拉应力逐渐过渡为高围压时的压应力。高围压时,虽然试件已处于三向受压状态,但其破裂仍表现为典型的张性破裂。从另一意义上讲,处于高围压环境中的岩石,其内部不可能存在拉应力,拉应力只在低围压状态中存在。若岩石的应变抗拉强度由εt表示,即使岩石三向受压,张性破裂的εt始终是拉应变,岩石的抗拉强度由应变来表征似乎更合理。εt先随围压的增大而增大,当围压超过某一特征值后,εt反随围压的增大而有所减少。 将上述结果应用于岩体(或地震)破裂,可以证明,当岩体内存在σ_3<μ(σ_1+σ_2)的应力状态时,即使三向受压,岩体照样会出现张性破裂。由此认为,地震的震源也存在着张性破裂的可能。     

2020年1月19日伽师6.4级地震强震动记录特征分析

以新疆强震动台网获取的伽师6.4级地震的42组126条原始加速度记录为依据,对强震动记录时程、幅值、频谱三方面进行分析。结果表明,此次地震获取的最大加速度峰值为633.3cm/s²,仪器地震烈度为Ⅸ度;在震中距200km以内两水平向与垂直向加速度峰值比在1~3之间,速度峰值比在0~4之间。分析此次地震三分向加速度峰值衰减关系,0~50km范围内地震峰值加速度观测值在分区地震动衰减关系(Yu13)长轴预测值误差范围之内,高于南天山西段土层衰减关系(Zhang)预测值;水平向加速度反应谱卓越周期主要集中在0~0.5s,垂直向集中在0~0.2s。65XKR台水平向反应谱高于Ⅷ度罕遇地震设计反应谱,峰值卓越周期为0.48s;垂直向反应谱高于Ⅷ度罕遇地震设计反应谱,峰值位于高频段。     

人工触发闪电通道的发光特征

利用成像率为１０００幅／秒的高速数字化摄像系统在３８０ｍ的极近距离对人工触发闪电通道的发光特征进行了观测的研究。人工引发闪电除了采用的火箭地带接地导线的触发方式外还发展导线下端不接地的空中触发闪电的新技术。结果表明,闪电通道的发光截面基本上呈对称型。     

Effect of Pumice and Sand on the Sustainability of Granular Iron Beds for the Aqueous Removal of CuII,NiII, and ZnII

Current knowledge of the basic principles underlying the design of Fe⁰ beds is weak. The volumetric expansive nature of iron corrosion was identified as the major factor determining the sustainability of Fe⁰ beds. This work attempts to systematically verify developed concepts. Pumice and sand were admixed to 200 g of Fe⁰ in column studies (50:50 volumetric proportion). Reference systems containing 100% of each material have been also investigated. The mean grain size of the used materials (in mm) were 0.28 (sand), 0.30 (pumice), and 0.50 (Fe⁰). The five studied systems were characterized (i) by the time dependent evolution of their hydraulic conductivity (permeability) and (ii) for their efficiency for aqueous removal of Cu^II, Ni^II, and Zn^II (about 0.3 mM of each). Results showed unequivocally that (i) quantitative contaminant removal was coupled to the presence of Fe⁰, (ii) additive admixture lengthened the service life of Fe⁰ beds, and (iii) pumice was the best admixing agent for sustaining permeability while the Fe⁰/sand column was the most efficient for contaminant removal. The evolution of the permeability was well‐fitted by the approach that the inflowing solution contained dissolved O₂. The achieved results are regarded as starting point for a systematic research to optimize/support Fe⁰ filter design.     

Tectonic Characteristics and Evolution of Bohai Bay Basin, China

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