常规土类动剪切模量比和阻尼比试验研究

采用共振柱自振试验方法给出国内常规土类动剪切模量比G／Gmax和阻尼比λ变化的平均曲线,推荐值和包线,使用的共振仪是由工种力学研究所原有共振柱改装而成,并经试验验证了改装后仪器的精度可靠性,试验土类包括粘土,粉质土,粉土,砂土,淤泥和淤泥质土,土样来自国内十余个不同地区,采用折线双曲线拟合G／Gmax,λ随γ衰减关系,其中参数a和b由最小二乘法对每次试验结果回归分析得到,对同类土,将所有的a,b 值平均,用均值a和b给出动剪切模量比和阻尼比与剪应变关系,从而得到了此类土G/Gmax,λ随γ变化曲线及推荐值,试验是在两种固结压力下进行,因而得到的结构分别适用于土体埋深小于10m和埋深10m-20m之间的两种情况。     

A gravel lobe deposit in the prodelta of the Doumsan fan delta (Miocene), SE Korea

The Doumsan fan-delta system in the Pohang Basin (Miocene), SE Korea comprises tripartite components of Gilbert-type topset, foreset, and bottomset environments with an extended prodelta in the deeper part (a few hundred metres deep). The present study documents sedimentologic features and origin of a gravel body (here interpreted as a gravel lobe) formed in the prodelta region of the Doumsan fan delta. The gravel lobe lies on sandy mud deposits and is capped by a thick massive sand bed. It extends for more than 1.5 km with a height of up to 30 m and shows a narrow tongue-like geometry. Eight sedimentary facies have been distinguished to describe characteristic features of the gravel lobe and the associated deposits. Of these, three types of gravelly sedimentary facies are important with regard to volumetric contribution and depositional processes: (1) crudely stratified pebble-grade conglomerate; (2) disorganized, clast-rich pebble(-to-cobble)-grade conglomerate; and (3) matrix-rich, bimodal cobble-grade conglomerate. The former two types dominate the central part of the lobe where they are not accompanied by sand beds, whereas the latter, as subordinate units, is prevalent in the fringe which otherwise is dominated by thick sandy mud deposits. The stacked successions of crudely stratified pebble-grade conglomerate are representative of the active aggradational phases of the gravel lobe, whereas the occurrence of channels within the lobe reflects that the gravel lobe prograded under the influence of subaqueous channel systems. The gravel lobe resulted from catastrophic disturbance (slumping) on the foreset region that further caused the development of channel systems, promoting efficient transport of gravelly sediments. This type of deposit may represent an important additional category of low-efficiency subaqueous fans.     

Gravelly spit deposits in a transgressive systems tract: the Pleistocene Higashikanbe Gravel, central Japan

The Pleistocene Higashikanbe Gravel, which crops out along the Pacific coast of the Atsumi Peninsula, central Japan, consists of well‐sorted, pebble‐ to cobble‐size gravel beds with minor sand beds. The gravel includes large‐scale foreset beds (5–10 m high) and overlying subhorizontal beds (0·5–3 m thick), showing foreset and topset structure, from which the gravel has previously been interpreted as deposits of a Gilbert‐type delta. However, (1) the gravel beds lack evidence of fluvial activity, such as channels in the subhorizontal beds; (2) the foresets incline palaeolandwards; (3) the gravels fill a fluvially incised valley; and (4) the gravels overlie low‐energy deposits of a restricted environment, such as a bay or an estuary. The foresets generally dip towards the inferred palaeoshoreline, indicating landward accretion of gravel. Reconstruction of the palaeogeography of the peninsula indicates that the Higashikanbe Gravel was deposited as a spit similar to that developed at the western tip of the present Atsumi Peninsula, rather than as a delta. According to the new interpretation, the large‐scale foreset beds are deposits on the slopes of spit platforms and accreted in part to the sides of small islets that are fragments of the submerging spit during relative sea‐level rise. The subhorizontal beds include nearshore deposits on the spit platform topsets and deposits of gravel shoals or bars, which are reworked sediments of the spit beach gravels during a transgression. The lack of spit beach facies in the subhorizontal beds results from truncation by shoreface erosion. Dome structure, which is a cross‐sectional profile of a recurved gravel spit at its extreme point, and sandy tidal channel deposits deposited between the small islets were also identified in the Higashikanbe Gravel. The Higashikanbe Gravel fills a fluvially incised valley and occupies a significant part of a transgressive systems tract, suggesting that gravelly spits are likely to be well developed during transgressions. The large‐scale foreset beds and subhorizontal beds of gravelly spits in transgressive systems tracts contrast with the foreset and topset beds of deltas, characteristic of highstand, lowstand and shelf‐margin systems tracts.     

抗液化排水井(桩)间距确定方法的研究

运用土力学、土动力学以及地下水向集水建筑物运移的非稳定流理论等的有关原理,提出了一种确定防止饱和砂土液化排水井（桩）间距的计算方法,并通过试验对这一方法进行了验证。     

Gravel Image Segmentation in Noisy Background Based on Partial Entropy Method

INTRODUCTIONImage thresholding has been widely used in many areas,and there are many methods for thresholding. But it is verydifficult to segmentgravel objects,because of wide variation ingray levels and particle dimensions and the presence of manysmall objects in the background corrupting the image bystationary or white noise. Shannon’s entropy is a concept ininformation theory,which means the more information,theless the entropy value. By m eans of entropy concept,researchers have prop…     

呼伦贝尔沙质草原风蚀坑研究（Ⅱ）:发育过程

沙质草原风蚀坑的发育过程主要有以下几个阶段:风蚀裸地→土层破口→活跃发展风蚀坑→固定风蚀坑→消亡风蚀坑。固定或消亡的风蚀坑可能活化,并重新进入活跃发展阶段。地貌发育则相应地经历典型草原景观→沙漠-草原景观→沙地-草原景观的总体演变过程。风蚀坑的发展有极限控制。但是各类沙丘的固定非常困难,有向大规模典型沙漠景观发展的高度危险。风蚀坑的形成发展和植被的演替将平坦单调缺水的典型草原改造成地形起伏多变,并有星散分布的风蚀坑湿地点缀其间、植被类型丰富多样的乔、灌、草相结合的沙地疏林草原。因地制宜地保护和利用沙质草原,可以保持其生态系统不致恶化并促进其不断优化。     

抽真空引起周围土体竖向变形的有限元分析

真空预压法加固深厚超软土地基时,一方面使地基土体产生侧向收缩变形,有利于地基的稳定;但另一方面向真空预压区的侧向变形对周围房屋、地下管线、道路等建筑物也产生不利影响,甚至会出现管道断裂、围墙倒塌、路堤被毁等严重工程事故。结合真空预压加固软基工程中出现的对周围环境影响的问题,进行了考虑土体拉裂影响的有限元分析,研究抽真空过程及加固区外不同距离、不同土体深度沉降的变化规律。研究结果表明,采用Biot固结理论、考虑土体拉裂的有限元计算结果与现场加固区外土体沉降及影响区范围的实测结果基本一致。     

新亚欧大陆桥新疆段环境灾害分布规律

根据实地调查和收集到近四十年资料、分析新亚欧大陆桥新疆段环境灾害成因、类型及成灾方式,阐明了陆桥新疆段以洪水、风沙灾害为主要类型的灾害特点,通过对不同灾害类型的时空强分布的统计分析,揭示了灾害过程春季３～４月以盐碱土不良路基、风沙灾害为主,夏季６～７月份以洪水为主的灾害时空活动特点和区域分异规律。     

内蒙古奈曼旗中部沙地土壤剖面特征

通过对奈曼旗中部不同沙地土壤剖面特征和有机质含量分布的分析认为:灌溉农田土壤具有8层结构,沙层与粘土层交错叠置。旱作农田土壤虽然也具有8层结构,但是只有一层粘土,撂荒地土壤只有3层,而且完全是沙层,保水保肥性能最差。此外,灌溉农田土壤0~30 cm土层的有机质的含量约0.712 g·cm^-3,旱作农田和撂荒地相应土壤层的有机质含量分别只有0.403g·cm^-3和0.420 g·cm^-3。同一土壤剖面的有机质含量随着深度的增加而减少。     

豫北沙地油桃设施促早栽培技术研究

油桃设施促早栽培是国内近年来兴起的一项高新农业技术,为了促进油桃设施栽培在豫北沙地的稳步发展,使之成为沙地高效开发的果产业之一,本文根据果树设施栽培环境因子的变化规律,借鉴国内油桃设施栽培的成功经验,结合豫北沙地自然、社会经济的状况,建立沙地油桃高效设施栽培模式,提出适宜的设施类型、结构,适栽品种,配置模式,栽植密度及配套栽培管理技术。