汶川地震庙子坪特大桥主桥箱梁开裂震害分析          下载免费PDF全文

童磊  王东升  王荣霞 《世界地震工程》2020,(3):161-171

2008年汶川地震中庙子坪特大桥主桥箱梁开裂严重,并在两个端部（过渡墩处）有较大的横向残余位移。为深入了解主梁开裂震害原因,选取桥址附近台站实测的八条强震动记录及常用El Centro等波作为输入,考虑箱梁施工过程及初始应力影响,通过时程分析进行数值模拟并与实际震害比较。结果表明:不同地震波输入下得到的箱梁高应力区与实际开裂区吻合较好,预示箱梁开裂震害不属于偶然现象。箱梁在主墩处、边跨和中跨合龙段区域处的顶板,边跨1/6~1/2及中跨1/4~3/4区域处的腹板,边跨和中跨合龙段及其相邻2~3个节段处的底板,在地震中易出现高拉或压应力区。地震过程中估计纵向预应力筋应力增加接近100MPa,横桥向挡块破坏降低了跨中箱梁的拉和压应力,对箱梁开裂震害有一定减轻作用。  相似文献   

矿山地质环境治理中坚硬岩石削坡方法比较和优化          下载免费PDF全文

高骏 《探矿工程》2020,47(12):79-85

对各种岩性的山体进行削坡减载是矿山地质环境治理项目中的重要工程。以江苏省某地矿山环境治理项目为例,对高边坡坚硬石体削坡的“露岩爆破法”、“膨胀剂破碎法”、“二氧化碳致裂法”、“机械破碎法”4种方法进行了比较和优化,在分析了该工程的施工重点、难点的基础上,选用“二氧化碳致裂法”施工,取得了良好的效果。详细介绍了工程的施工工艺、施工过程等,总结了相关经验,对用“二氧化碳致裂法”施工进行了进一步的思考。  相似文献   

A novel type of neural networks for feature engineering of geological data:Case studies of coal and gas hydrate-bearing sediments     

《地学前缘(英文版)》2020,11(5):1511-1531

The nature of the measured data varies among different disciplines of geosciences.In rock engineering,features of data play a leading role in determining the feasible methods of its proper manipulation.The present study focuses on resolving one of the major deficiencies of conventional neural networks(NNs) in dealing with rock engineering data.Herein,since the samples are obtained from hundreds of meters below the surface with the utmost difficulty,the number of samples is always limited.Meanwhile,the experimental analysis of these samples may result in many repetitive values and 0 s.However,conventional neural networks are incapable of making robust models in the presence of such data.On the other hand,these networks strongly depend on the initial weights and bias values for making reliable predictions.With this in mind,the current research introduces a novel kind of neural network processing framework for the geological that does not suffer from the limitations of the conventional NNs.The introduced single-data-based feature engineering network extracts all the information wrapped in every single data point without being affected by the other points.This method,being completely different from the conventional NNs,re-arranges all the basic elements of the neuron model into a new structure.Therefore,its mathematical calculations were performed from the very beginning.Moreover,the corresponding programming codes were developed in MATLAB and Python since they could not be found in any common programming software at the time being.This new kind of network was first evaluated through computer-based simulations of rock cracks in the 3 DEC environment.After the model's reliability was confirmed,it was adopted in two case studies for estimating respectively tensile strength and shear strength of real rock samples.These samples were coal core samples from the Southern Qinshui Basin of China,and gas hydrate-bearing sediment(GHBS) samples from the Nankai Trough of Japan.The coal samples used in the experiments underwent nuclear magnetic resonance(NMR) measurements,and Scanning Electron Microscopy(SEM) imaging to investigate their original micro and macro fractures.Once done with these experiments,measurement of the rock mechanical properties,including tensile strength,was performed using a rock mechanical test system.However,the shear strength of GHBS samples was acquired through triaxial and direct shear tests.According to the obtained result,the new network structure outperformed the conventional neural networks in both cases of simulation-based and case study estimations of the tensile and shear strength.Even though the proposed approach of the current study originally aimed at resolving the issue of having a limited dataset,its unique properties would also be applied to larger datasets from other subsurface measurements.  相似文献   

水下收缩裂隙天然实验研究中获得的新认识   总被引：4，自引：0，他引：4       下载免费PDF全文

赵振宇周瑶琪  马晓鸣郑平 冀国盛 《地质论评》2007,53(3):306-317,I0001

通过青岛市唐岛湾沿岸7个实验工区的考察测试、实验分析、数据处理等,对现代泥质沉积物水下收缩裂隙的整体形成过程、定量分级、各参数间拟合关系、开裂规律以及充填物沉积模式等进行了详细研究,并且建立了相应的地质演化模型。裂隙整体形成过程分4个阶段,依次为:泥水混合物初始混浊阶段;沉积物压实稳定阶段;裂隙形成阶段以及裂隙充填阶段。裂隙形态定量分级可分别用横缝长、纵缝长、裂隙面积和基块面积等参数表示,共分4级。其中裂隙各参数之间的拟合关系以及开裂规律地质建模分析等,对于定量描述裂隙形态、结构、变化规律,预测区域性裂隙规模、判别区域沉积环境等具有重要意义。沙泥质地层裂隙开裂过程中的异常高压作用(形成机理与大地构造中的异常高压相似)以及裂隙分叉角度的统计分析(最多为90°,其次为120°)均属首次提出。其中异常高压作用对于初始裂隙的形成、沉积物粒间水的有效排出以及主要渗流通道的发育起到了重要作用。单一泥质地层裂隙内充填物沉积模式与沙泥互层的多旋回地层略有差异,主要表现为沙层的润滑作用以及对早期裂隙内充填物类型的影响。裂隙纵剖面中生物发育层的出现,对于裂隙内充填物的物理、化学性质将产生重要影响。  相似文献   

Seismic Behaviour of Slightly Reinforced Concrete Walls: Experiments and Theoretical Conclusions     

Philippe Bisch  André Coin 《Bulletin of Earthquake Engineering》2007,5(1):45-65

In order to develop new standards related to structures in seismic regions, a series of research programmes has been conducted on slightly reinforced structural walls commonly used in France. Based on these researches, a method of design of such walls submitted to a seismic action has been set up. This method used in the PS92 code differs from that used for ductile walls, where a plastic hinge can develop at the base of the wall. The analysis is similar to the push over analysis presently given in Eurocode 8. These various researches have confirmed the validity of the design concept developed for the PS92 code, on one hand, and highlighted a number of phenomena linked to the non linear behaviour of reinforced concrete walls, on the other hand. The present article aims at presenting a synthesis of the results obtained during these research programmes.  相似文献   

Development of micro-scale joints in volcanic rocks under thermal stress     

Susanta Kumar Samanta 《Journal of Earth System Science》2001,110(3):191-203

Petrographic studies of samples of the Rajmahal basalt reveal a variety of microscopic joints within phenocrysts, which seem to have developed under the influence of thermal stresses during cooling. The theoretical analysis shows that:

–	•thermal stresses develop in a system only under unsteady state of cooling,
–	•the stresses responsible for the development of joints are tensile in nature, and
–	•the magnitude of stresses increases with increasing rates of cooling.

In order to understand the effects of cooling rate on the mode of jointing, analogue model experiments were performed by quenching melt films of organic, crystalline materials under varying cooling conditions. In experiments, non-branching linear joints developed at relatively lower rates of cooling by a process of sub-critical crack propagation. On the other hand, at higher rates of cooling the mechanism of crack propagation was essentially supercritical leading to the development of branching joints.  相似文献   

塔里木盆地塔中地区奥陶系构造－沉积模式与碳酸盐岩裂缝储层预测   总被引：5，自引：1，他引：4  

魏国齐  贾承造  宋惠珍  施央申  卢华复  李亚红 《沉积学报》2000,18(3)

奥陶系碳酸盐岩是塔中地区油气勘探的重要目的层。本文在讨论塔中地区奥陶纪区域构造背景和奥陶系岩性段划分的基础上,建立了塔中地区奥陶系构造－沉积模式,并用三维有限元数值模拟方法对塔中地区有利碳酸盐岩裂缝储层发育区进行了预测,以期指导塔中地区碳酸盐岩的油气勘探。  相似文献   

随机固-热耦合模型与岩石热破裂数值试验研究   总被引：4，自引：2，他引：2  

康健  赵明鹏  梁冰 《岩土力学》2005,26(1):135-139

1. 大连轻工业学院 信息科学与工程学院,大连 116034;2. 辽宁工程技术大学 力学与工程科学系,辽宁 阜新 123000  相似文献   

Geochemistry and origin of deep-seated cracked gas on the northern slope of the Dongying Sag, Shandong Province     

Xiangchun Chang  Zuozhen Han  Youde Xu  Xiaofei Shang  Chengpeng Yan 《中国地球化学学报》2011,30(3):353-358

Deep-seated cracked gas exploration was achieved great breakthrough in Es4L of the Minfeng area on the northern slope of the Dongying Sag. Carbon isotopic and molecular compositions studies revealed the characteristics of wet gas and a normal trend of carbon isotopic composition. Empirical cutoff points of δ13C2 and δ13C3 and light hydrocarbon compositions distinguished the cracking gas as sapropelic gas. Variations in i/nC5, i/nC4 and δ13C2 fur-ther confirmed that the gas was cracked from residual kerogen. Source characteristics indicated that the gas was de-rived from mature-highly mature source rocks of Es4 with kerogen type II being dominant mixed with some oil-cracking gas. Burial history modeling indicated that there were two hydrocarbon charging periods in Es4L reser-voirs. The first period refers to the Guantao-Minghuazhen stage dominated by oil charging, while the second period refers to the Minghuazhen stage and has been dominated by cracked gas charging till now.  相似文献   

Probabilistic lifetime assessment of marine reinforced concrete with steel corrosion and cover cracking     

陆春华  金伟良  刘荣桂 《中国海洋工程》2011,25(2):305-318

In order to study the durability behavior of marine reinforced concrete structure suffering from chloride attack,the structural service life is assumed to be divided into three critical stages,which can be characterized by steel corrosion and cover cracking.For each stage,a calculated model used to predict the lifetime is developed.Based on the definition of durability limit state,a probabilistic lifetime model and its time-dependent reliability analytical method are proposed considering the random natures of influencing factors.Then,the probabilistic lifetime prediction models are applied to a bridge pier located in the Hangzhou Bay with Monte Carlo simulation.It is found that the time to corrosion initiation t0 follows a lognormal distribution,while that the time from corrosion initiation to cover cracking t1 and the time for crack to develop from hairline crack to a limit crack width t2 can be described by Weibull distributions.With the permitted failure probability of 5.0%,it is also observed that the structural durability lifetime mainly depends on the durability life t0 and that the percentage of participation of the life t0 to the total service life grows from 61.5% to 83.6% when the cover thickness increases from 40 mm to 80 mm.Therefore,for any part of the marine RC bridge,the lifetime predictions and maintenance efforts should also be directed toward controlling the stage of corrosion initiation induced by chloride ion.  相似文献