台湾海峡西岸第四纪沉积层中的老红砂

本文对采自福建沿海的老红砂作了粒度分析、矿物鉴定和石英电镜扫描。结果表明,组成老红砂的成分主要为中细砂,砂含量大于70%,粘土和粉砂含量较少。概率累积曲线多为跳跃、悬浮两段式,其次为滚动、跳跃、悬浮三段式。轻矿物以石英为主,长石含量居次。含量较高的重矿物有磁铁矿、钛铁矿、白钛石,其次有锆石、赤铁矿、褐铁矿、电气石、绿帘石等。文章对老红砂的成因提出一些粗浅的看法。     

EXPERIMENTAL AND FIELD STUDY ON MINING-PIT MIGRATION

1 INTRODUCTION Because of the large quantity of sand and gravel in their beds, rivers have always been considered as a major source of sand and gravel for civil works. Acceptable quality, ease of extraction and economy are some of the reasons could be mentioned. Unfortunately, specific laws and regulations regarding the safe in-stream mining have not been provided for users and officials. What should be taken into account are the effects of over-mining of sand and gravel, which can cause …     

Dynamic processes of a simple linear dune—a study in the Taklimakan Sand Sea, China

Samples of dune sands, surveys of the morphology and field measurements of wind velocity and direction of a simple linear dune in Taklimakan Sand Sea show that the airflow and sand flux vary with the change of wind direction on the dune surface. Decrease of the airflow stress on the lee flank does not result in much decrease of the sand flux because of the low threshold shear velocities and the airflow conditions. There are no significant relations between the sand flux on the lee flank and the angle of incidence of the airflow. The low threshold shear velocities and the maintenance of the sand flux at the lee flank are the main mechanisms keeping the linear shape of the dunes. Measurements of the sand flux shows that it reaches a maximum on the crest of the dune. The grain size of the transported sands has some differences compared to that of the dune surface. The sands transported are finer than that on the dune surface, but better sorted under the influence of the medium to low wind activity. The field experiment results exhibit that it is possible for the dunes to be shaped as linear dunes during the processes of accumulation and elongation.     

沈阳地区沙尘天气分析

本文总结了沈阳地区沙尘天气的时空分布特点，从天气条件、地表自然条件(沙源)两方面分析了沈阳地区沙尘天气的成因，总结了沈阳地区预报沙尘天气时应参考的5个因素。     

塔河油田卡拉沙依组砂组沉积相与储层研究

卡拉沙依组砂岩是塔河油田石炭系重要储层，从上到下分为4个砂组，即Ⅰ砂组、Ⅱ砂组、Ⅲ砂组及Ⅳ砂组，根据岩石组合特征、岩石粒度、分选性、以及沉积构造等特征，可得出Ⅰ砂组为较典型的扇三角洲沉积环境；Ⅱ-Ⅳ砂组为潮坪环境，其中Ⅲ砂组沉积时的古环境水动力相对最强，以潮间带下部为主，储层砂体最发育，单个砂体的厚度也最大，为纵向上最好储层段。     

风沙流中沙粒浓度分布的实验研究

利用粒子图像测速技术（PIV）,在风洞内对与天然沙接近的石英沙风沙流沙颗粒浓度沿高度分布进行了研究。对 3种不同轴线风速研究结果表明,风沙流中沙粒浓度沿水平方向基本不变,而随高度呈指数衰减,而且其衰减速率与风速密切相关。风速越大,衰减速率越慢;风速越小,衰减速率越快。风沙运动一旦发生时,靠近沙床表面的沙粒浓度随风速变化很小,可以认为趋于稳定,达到最大值。     

黄土沉积物原生组分磁化率与风力的物质分选

本研究选取我国西北地区典型荒漠表土和黄土-古土壤序列样品为研究对象,探讨黄土沉积物及其潜在物源区表土的原生磁性矿物浓度在不同粒级间的变化规律、黄土剖面中粒度与磁化率的关系,以验证中国黄土沉积物中磁性组分在搬运过程中是否存在分选作用及其变化规律。来自西北地区表土的地质证据表明,磁性组分主要集中于>63 μm和31~63 μm粒径组分,并以后者的含量最高;与之相对应,黄土沉积中原生磁性组分主要集中于31~63 μm粒径组分,但>63 μm粒径组分不再是主要载磁组分,其磁性显著低于31~63 μm粒径组分。同时,多个剖面的证据表明黄土沉积的原生磁化率与31~63 μm粒径组分的含量是同相位变化的,进一步支持沉积物中原生组分的磁化率受到风动力的分选作用影响。需要强调的是,沉积物原生磁化率的主要载磁粒径组分为31~63 μm的颗粒物,而并非最粗粒组分。本研究结果暗示,相较于沉积物的全样粒度,干旱半干旱地区风成沉积的磁化率在指示古风场强度方面具有潜力。

     

Prediction method of sand-movement direction in water by geochemical elements

The analysis of sand samples by x-ray fluorescent spectroscopy (XRF) gives the ratio of the geochemical elements to construct the sand samples. The x-ray analysis therefore shows the geochemical characteristics of sand in the sampled area. In this study, sand is sampled on coasts and rivers of the Noto Peninsula to determine the geochemical elements and to show the geological characteristics that occur, especially iron and calcium. The experiments show the effect of rivers and Kotogahama beach on iron and calcium, respectively. Applying the method of ratio matching to the measured data of the geochemical elements, the direction of movement of sand on the coast is determined by considering the correlation matrix and the ratio of geochemical elements between sand samples at two locations. The predominant longshore direction movement of sand offshore in the study area is from south to north. Sand in rivers is not directly transported to adjacent beaches; however, offshore sand is transported to beaches. The estimated direction of movement of sand longshore near coastal structures agrees with observations. The proposed method to predict the direction of movement of sand gives the correct one in comparison with the observed data in rivers.     

A laboratory study of the self sealing behaviour of a compacted sand–bentonite mixture

Bricks made of compacted sand–bentonite mixture are considered as a possible engineered barrier to isolate high-level radioactive waste at great depth. This work is aimed at investigating some specific effects related to the presence of discontinuities at the contact between the bricks and the excavation wall. In order to do this, an experimental device was developed in the laboratory. The model is made up of a specially designed infiltration cylinder which allows the precise definition of a planar discontinuity between the compacted specimen (a sand–bentonite mixture made up of sand and Kunigel clay from Japan) and a metal wall. During hydration and subsequent specimen swelling, the planar wall is filled, resulting in a healing process. Three total pressure gauges placed along the wall allow a detailed observation of the increase in total stress against the wall. After different periods of swelling, the maximum resistance of the specimen–wall interface to pressure was tested by imposing a pressure increase through a porous stone placed at one end of the cylinder. It was found that the maximum pressure supported by the interface is a function of the initial thickness of the discontinuity and the initial density of the specimen. It was also found that the maximum sustainable pressure depends linearly on the elapsed time. These results are of interest for optimizing water infiltration procedures in either mock-up tests or real disposal systems. If the maximum sustainable pressure at the interface is known, it is possible either to ensure homogeneous hydration of a mass of bricks by respecting the maximum injection pressure limit or to accelerate hydration by forcing water paths along the discontinuities.