高压喷射注浆用于护坡防渗工程     

魏文晶 《地质与勘探》1998,34(2):58-60

叙述了高压喷射注浆技术应用于护坡防渗工程的条件,要求和与钻孔灌注桩的结构方式,以及施工中注意的问题,并对此提出了一些新的认识。  相似文献   

软土深基坑中的角落效应   总被引：1，自引：0，他引：1  

吕锋  吴浩 《水文地质工程地质》1998,(2)

在对软土深基坑档墙与土体的变形、破坏等基坑支护失事原因分析的基础上,提出基坑角落效应的概念,指出角落效应为当前软土深基坑工程设计与施工所忽视,分析了角落效应的形成机理及其综合特性,讨论了角落效应对基坑稳定性的影响及其治理建议。  相似文献   

重庆市浅埋地下洞室安全顶板厚度研究   总被引：17，自引：0，他引：17  

黄润秋  陈尚桥  黄家渝  何平 《工程地质学报》1998,(2)

本文在参考已有资料的基础上,分析了重庆市浅埋地下洞室安全顶板厚度的影响因素。采用有限单元数值模拟法研究了地基与洞室相互作用下的破坏机制,以及各影响因素对浅埋地下洞室安全顶板厚度的影响及相关变化规律,并用逐步线性回归的方法得出了一个能综合考虑各影响因素的安全顶板厚度的预测模型。本文最后还分析了顶拱裂隙对安全顶板厚度的影响。  相似文献   

RBF神经网络在深基坑监测预测中的运用     

曾洪飞  周健  贾斌 《上海国土资源》2004,(2):44-47

该文简要介绍了：RBF神经网络相对于BP神经网络的优点，分析了RBF神经网络的模型和结构。在此基础上通过Matlab编程语言建立了一预测深基坑工程监测项目的重要内容——墙体位移的RBF神经网络模型，经过工程实例验证了该模型的正确性，说明RBF神经网络在对深基坑工程监测项目的预测是可行和有效的。  相似文献   

Probabilistic Horizontal Stress Ratios in Rock   总被引：1，自引：0，他引：1  

Zekai en  Bahaaeldin H. Sadagah 《Mathematical Geology》2002,34(7):845-855

Prior to excavation, any point in a rock mass is subjected to stress, which has to be considered in the overall stress distribution after the excavation work is completed. Over the past three decades, empirical, analytical, and field studies have shown that the ratio of average horizontal stress to vertical stress plays a dominant role in engineering structure design. Notationally, this ratio is referred to as the coefficient of lateral stress K, which is a dimensionless positive quantity. The intent of this paper was to bring out the intrinsic characteristic of K with the use of probabilistic and statistical techniques, which have not been considered extensively in any previous context.  相似文献   

Hydrothermal Alteration and Cu-Au Mineralization at Nena High Sulfidation-type Deposit, Frieda River, Papua New Guinea     

Joseph Onglo Espi    Yoshimichi Kajiwara    Mike A. Hawkins  Tony Bainbridge 《Resource Geology》2002,52(4):301-313

Abstract. The Nena Cu‐Au deposit, located in the Frieda River mineral district of northwestern mainland Papua New Guinea, is a composite structurally‐lithologically controlled high sulfidation (HS) system. Its hydrothermal alteration and Cu‐Au mineralization are presented in this paper. Initially propylitized andesitic volcanics veined by epithermal quartz were pervasively superimposed by zoned HS alteration. The zonation grades from vuggy silica core to sulfur‐rich, pyritic silica‐alunite halo followed by pyrophyllite‐dickite‐kaolinite interval and finally to thin illite‐smectite margin, suggesting progressive decrease in temperature and increase in pH. This zonation is enveloped by chlorite‐epidote‐calcite‐gypsum alteration. The acid altered rocks were then invaded by multiple phases of pyrite, subsequently crosscut by quartz, vein alunite and barite. Then sequential deposition of bladed covellite, enargite, luzonite and stibioluzonite occurred from the NW to the SE portions of the deposit, forming a zonation suggestive of progressive decrease in temperature, sulfur fugacity and sulfidation stage. Most ore mineralization occurs in the vuggy silica core. Gold mineralization commenced from the transition of enargite to luzonite and continued throughout the stibioluzonite stage. Associated with gold deposition are Au‐rich pyrite, tennantite‐tetrahedrite, chalcopyrite‐bornite, native tellurium, electrum, calaverite, bismuthinite and galena. Native sulfur occupied the remaining cavities and represents the waning stage of the hydrothermal system. Fluid inclusions studies distinguished magmatic (>300–350d?C, 9–15 wt% NaCl equiv.) and meteoric (<150–200d?C, 1–2 wt% NaCl equiv.) fluids (Holzberger et al., 1996). Temperatures and salinities of fluid inclusions from barite associated with Cu sulfides show a general decrease from NW (330d?C, 9–15 wt% NaCl equiv.) to SE (172d?C, 10 wt% NaCl equiv.) parts of the deposit, indicating gradual entrainment of ground water (Hitchman and Espi, 1997). Interaction of magmatic fluids with meteoric water accompanied by changes in temperature, salinity, acidity and oxidation state of the resultant fluids is interpreted to have been the main cause of metal precipitation. Finally, supergene processes generated Au zone with an underlying chalcocite‐covellite‐digenite blanket over the primary sulfides at depth. Gold occurs as lattice constituent in scorodite, limonite‐goethite and jarosite. Chalcocite is more abundant and widespread than other Cu sulfides. Acidic fluids deposited powdery alunite and kaolinite, vein alunite and amorphous silica. Weakly secondary biotite‐quartz altered porphyry located below the known HS Cu‐Au deposit contains chalcopyrite‐bornite and is overprinted by quartz‐alunite‐pyro‐phyllite‐pyrite assemblage. This feature indicates close temporal, spatial and genetic relation between the two deposit types.  相似文献   

Soil parameter identification using a genetic algorithm   总被引：1，自引：0，他引：1  

S. Levasseur  Y. Malécot  M. Boulon  E. Flavigny 《国际地质力学数值与分析法杂志》2008,32(2):189-213

This paper is dedicated to the identification of constitutive parameters of the Mohr–Coulomb constitutive model from in situ geotechnical measurements. A pressuremeter curve and the horizontal displacements of a sheet pile wall retaining an excavation are successively used as measurements. Two kinds of optimization algorithms are used to minimize the error function, the first one based on a gradient method and the second one based on a genetic algorithm. The efficiency of each algorithm related to the error function topology is discussed. Finally, it is shown that the use of a genetic algorithm to identify the soil parameters seems particularly suitable when the topology of the error function is complex. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

BP神经网络融合预报在深基坑监测中的应用     

ZHANG Guan-yu  DENG Yong  YANG Zhen  YU Chun-ping 《测绘学院学报》2008,(4)

针对多传感器采集的多种变形信息,提出了利用BP人工神经网络的方法进行数据融合处理,以达到对变形体变形状况更加准确预报的目的。通过BP神经网络训练精确得到各种观测值权重,避免了人为主观因素的影响。利用该方法对多传感器数据进行横向预报可以实现对暂时损坏的传感器数据准确预测,保证数据的连续性。也可以采用该方法进行多传感器数据纵向融合预报。在广州某小区基坑综合监测项目中,预报结果与实际变形情况相吻合,取得了良好的效果。  相似文献   

中国重要生态空间生态用地变化与保护成效评估   总被引：1，自引：1，他引：0  

高吉喜  刘晓曼  王超  王勇  付卓  侯鹏  吕娜 《地理学报》2021,76(7):1708-1721

定量分析重要生态空间建立前后的生态保护成效,对于保障国家生态安全具有重要意义。本文以生态用地为切入点,从时间和空间双重角度,评估了中国重要生态空间构建的生态保护效果,以期能为国土空间分类分区管控提供科学依据。结果表明：① 2018年重要生态空间以生态用地为主导,具有良好的生态本底,体现了重要生态空间的发展定位和重要地位; ② 1980—2018年,重要生态空间内生态用地呈收缩趋势,但面积减少率低于全国平均水平,定量反映了重要生态空间的构建对生态的积极保护成效,总体来说生态用地变化基本处于稳定状态,扩大区域主要分布在退耕还林还草生态保护工程实施区,缩小区域集中在东北平原的粮食主产区和新疆绿洲农业地区,今后要重点加强管控;③ 3类重要生态空间内部生态保护成效有差异,国家级自然保护区生态用地面积比例最高,生态用地面积减少率最小、减少趋势最不明显、变化最为稳定,生态保护效果最好;④ 重要生态空间内生态用地面积比例高于周边外部区域,面积减少率低于外部区域,内、外保护成效具有明显梯度差异,说明重要生态空间的构建对生态保护的意义重大。  相似文献   

新建工程基坑开挖及结构施工对既建下卧隧道的影响研究   总被引：2，自引：0，他引：2  

徐长节  王伊丽  徐芫蕾  王金昌 《岩土力学》2015,36(11):3201-3209

随着城市建设的发展,地面工程和地下工程交叉建设的情况越来越多,新建工程对既有建筑产生影响的情况不可避免。因此,在保证既有工程结构安全的前提下建设新的工程已成为众多学者关注的重要问题之一。针对某已建隧道上方工程建设,分别采用Abaqus有限元数值模拟分析法和简化的规范角点法进行对比分析,评价隧道上方工程的基坑开挖及后续的结构施工对既建下卧公路隧道的影响。实施过程中的现场监测数据表明数值分析法和传统的土力学理论法在此类施工边界清晰、荷载施加明确的工程中的有效性并保障了工程的安全。研究还表明,二维分析模型不仅分析计算工作量相对较小,相较于考虑三维的实际工程安全性更有保障。本工程的成功经验可为类似工程的设计和施工提供有益的工程参考和借鉴。  相似文献