Preliminary Study on Loess Slumping Hazard between Northern Shaanxi and Western Shanxi along the Line of West-East Gas Transportation Project

INTRODUCTIONTheloess,widelydistributedinthenorthwestplateauofChina ,hasatalltimesbeenanimportantresearchsubjectofthestudiesonengineeringgeology.Duetotheunfavorableengineeringpropertiesofloess,aswellasthespecialtopog raphyandclimate ,thenorthwestloessplateauisaregionwithfrequentgeologicalhazardsandcomplicatedgeologicalengineeringproblems.Inthepast,mostoftheresearchersconsideredthelandslideasthemainandseriousformoffail ureoftheloessslopes,soloesslandslidesweregivenmoreattention (DuanandLuo…     

从陕西旬邑上新生界剖面看黄土高原新近系/第四系界线

新近系 /第四系界线在黄土高原大都以磁性 M/ Ga界线为界进行划分 ,它与岩性分界往往并不一致 ,后者都低或高于前者一小段距离。根据旬邑剖面的岩性、孢粉、古动物、磁化率、粒度及地化资料 ,并参考了其他一些剖面的岩性 ,认为以二者之间的过渡层底为界进行划分比较合理     

四川九寨沟地区黄土的初步研究

九寨沟地区的黄土孤立产出于海拔2300～2800m的洼地中,其内含古风化界面.通过对黄土的物质成分、结构、扫描电镜形貌、孢粉、ESR测年等分析测试,确定其为冰缘黄土,划分了九寨沟地区更新世冰期.     

微型贯入仪在长春黄土状土地基勘察中的应用

本文简要介绍了贯入试验及利用贯入试验测求土的工程地质性质指标的基本原理;通过对长春市一般建筑物主要持力层的黄土状土的微型贯入仪试验与室内土工常规试验的对比分析,经数理统计,建立了贯入阻力与土的有关工程地质性质指标的相关方程。这些相关关系,可用来快速划分土的稠度状态、土的压缩性及确定地基的承载力,对在本地区推广和使用微型贯入仪试验具有一定促进作用。     

泥河湾盆地的水下黄土堆积及其古气候意义

本文论述了泥河湾盆地第四纪河湖相地层中水下黄土堆积的特征，认为水下黄土堆积是介于气下黄土堆积河湖相沉积之间的一种过渡类型，水下黄土和气下黄土都是干冷气候条件下的产物，而河湖相沉积则形成于相对温湿的气候环境。在沉积剖面中水下黄土和河湖相沉积交替出现，形成水下黄土－河湖相沉积系列，这个系列反映了气候的周期性变化，它可以与我国洛川剖面的黄土－古土壤系列及深海岩芯V28－239的氧同侠素气候期，很好地进行对比。这为我国华北第四纪古气候地层序列的建立，又提供了一个重要的途径。     

沁水盆地黄土塬区三维地震勘探激发层位试验研究

沁水盆地黄土塬区地表黄土覆盖厚度不均，地震波速度差异较大，对地震勘探的激发有较大的影响.针对区域地表地层特点，设计地震地质模型，分析不同激发层位地震正演记录.结合试验区现场试验，对比分析了正演模拟记录.结果表明，合理的激发层位能够有效压制干扰波，突出目的层位反射波，提高黄土塬区三维地震原始资料的品质.     

Temporal and spatial relationships between soil erosion and ecological restoration in semi-arid regions: a case study in northern Shaanxi,China

ABSTRACT

To assess the effects of the Grain for Green Program (GGP) on soil erosion is essential to support better land management policies in the Chinese Loess Plateau. Studies on the evaluation of the effects of the GGP on soil erosion have garnered heightened attention. However, few studies examined the efficiency of GGP on soil erosion control through spatial relationship analysis. Thus, this study focuses on analyzing the spatial variation relationship between soil erosion and GGP in northern Shaanxi, Chinese Loess Plateau, from 1988 to 2015. The Universal Soil Loss Equation was used to quantify changes in soil erosion at the regional and watershed scales, and the Geographically Weighted Regression model was used to analyze the spatial relationships between land use and land cover (LULC) and soil erosion. Our results indicated that the major characteristic of LULC change during the GGP was a rapid increase of vegetation area and a rapid decrease of cropland. Bare lands contributed to the most serious soil loss, followed by croplands and sparse grasslands. The GGP had a globally positive influence on the decrease in soil erosion over the study area, but the amount of soil erosion in western and northern regions maintained a severe level. Spatial heterogeneity in the nature of the relationships among different vegetation, croplands, and soil erosion was also observed. The change rate of wood and the change rate of soil erosion in northern sub-watershed represented a negative relationship, while the change rate of sparse grassland was negatively correlated to the change rate of soil erosion in 21 sub-watersheds, account for 72% of the study area. The GGP implemented in northern sub-watersheds were more effective for soil erosion control than southern sub-watersheds. We propose that current areas of vegetation can support soil erosion control in the whole northern Shaanxi, but local-scale ecological restoration can be considered in northern sub-watersheds.     

黄土丘陵区生态重建“赈济退耕”及地域分异特征

“赈济退耕”是目前国家关于黄土丘陵区生态重建的主体措施。本文在总结“赈济退耕”措施及其基本特点的基础上 ,根据土地利用、耕地坡度分级数据和“赈济退耕”现行标准分别计算了黄土丘陵区各县退耕 2 5°和 15°以上坡耕地的面积和政策性补贴资金需求额度。在构建并采用退耕指数和政策性补贴资金密度指数等指标对 5 5个县 (市、区 )进行类型划分的基础上 ,分析了黄土丘陵区生态重建“赈济退耕”规模及政策性补贴地域分异特征     

一种分离富集中国黄土中微米级磁性物质的方法

微米级磁性矿物在黄土—古土壤序列中含量不足1％，为了满足多种测试的需要，要尽可能地富集磁性矿物。介绍一种富集方法，即程序地采用浸泡—搅拌(转速为5900r／min)—湿法磁选(磁场梯度范围为0．8—2．5T)—重液分选(d≥2．5)—干法磁选(激磁电流在1—2A之间)的方法，从西峰和段家坡第五层古土壤(分别简称为XS和DS)的上浮物和沉砂中富集出6个不同磁性的矿物组分。经磁化率(MS—2)、磁滞回线(MICROMag2900)测定、高倍显微镜(MPV—3)及扫描电镜(S—3500N)观测，矿物的分散度与磁性分选良好，精选的强磁性组分(XS—4J和DS—4J)中磁性矿物含量约占该组分的30％，富集的磁性矿物种类多，包括含铁粘土、碎屑状磁性矿物和自生磁性矿物，磁选出的矿物代表性强并能满足多项分析测试的需要。湿法磁选(程序3)是流程中操作最复杂的一步，根据XS样的实测结果，这一步磁选的回收率为87．2％。