单位圆外域到任意开挖断面隧洞外域共形映射的计算方法

将复杂开挖断面为边界的力学问题转化成单位圆为边界的力学问题,是利用复变函数理论开展地下隧洞围岩力学分析的前提。从黎曼存在定理出发,建立了以洛朗级数有限项表示的单位圆外域到任意开挖断面隧洞外域的共形映射函数。根据边界对应原理,将域到域的共形映射问题转化成单位圆周线到任意开挖断面隧洞边界线的共形映射问题。从三角插值理论出发,采用奇偶插值点反复相互迭代对映射函数的求解开展了研究。为快速地进行迭代计算,采用法线逼近法进行计算点（映射点）调整。提出了以映射边界线与实际开挖洞形边界线之间的绝对误差作为迭代计算的收敛条件,保证了共形映射精度。给出了3个开挖断面隧洞映射函数的求解算例,并将研究结果与文献中的方法进行了比较。结果表明,提出的单位圆外域到任意开挖断面隧洞外域共形映射的计算方法具有操作简单、精度高和收敛快等特点。     

大直径变径桩竖向承载特性模型试验研究(I)

变径桩在桥梁桩基和软土地基处理得到了一定程度的应用,对其承载特性和工作机制的研究十分必要。通过室内大型模型试验,对大直径变截面单桩的荷载与沉降关系、桩侧摩阻力分布形式、桩身内力和桩端、变截面处的破坏模式等问题进行了探讨,试验结果表明,在桩顶截面相同的情况下,变截面桩竖向承载特性受变截面比影响显著,变截面比越小,竖向极限承载力越小。模型试验P-S曲线不存在最优变截面比,变截面比设计受桩横向受力特性的控制。变截面处土体挤土效应的发挥是以牺牲桩顶位移为代价,在只有到达一定桩身位移时,才体现明显的挤土效应,使承载力提高。     

湘鄂西—川东中生代陆内递进扩展变形: 来自裂变径迹和平衡剖面的证据

从湘鄂西到川东近400 km宽阔的中上扬子陆内中古生界变形是江南—雪峰陆内造山作用向西北方向递进扩展变形的结果.利用磷灰石裂变径迹年龄测定和埋藏热历史模拟以及雪峰山—华蓥山构造剖面的平衡演变分析方法, 揭示出自湘鄂西向川东华蓥山构造变形发展的时代从165 Ma到95 Ma, 具有递进变新的趋势.湘鄂西断褶带厚皮构造变形缩短率小于川东断褶带薄皮构造的变形缩短率, 但侏罗纪时期湘鄂西断褶带的缩短速率却明显大于早白垩世早中时期川东断褶带东南段的缩短速率, 而早白垩世早中时期川东断褶带东南段的缩短速率又大于早白垩世晚期川东断褶带北西段的缩短速率, 反映基底卷入程度和推挤力源的强度大小是控制缩短率和缩短速率的主要原因.这些结果表明湘鄂西—川东中生代陆内变形具有大跨度穿时递进扩展的特征和方式, 并且由于基底的差异和卷入程度的不同以及滑脱层参与深度和程度的不同, 不同构造带缩短率和缩短速率的变化反映出明显的陆内变形及其动力学的差异.研究推测, 如果江南—雪峰隆起是原地或准原地体, 则湘鄂西—川东陆内构造递进扩展变形的"发动机"在桃源—怀化一线, 该线亦是江南—雪峰中生代陆内造山作用开始发轫并向南北两侧呈花状扩展的位置.      

库车前陆冲断带盐构造区平衡剖面研究

通过计算库车前陆冲断带古近系库姆格列木组含盐层系初始沉积厚度,并以此作为地质约束条件,采用分层复原法对该区地质剖面进行平衡复原。复原结果表明,库车前陆冲断带南北向总缩短量为18~31km,缩短率为16%~34%。其中新生代变形强度最大,缩短率接近15%。新生代最强烈的构造变形又是发生在库车组开始沉积后的喜马拉雅运动晚期,该时期缩短量已超过新生代缩短量的80%,缩短速率达到2.43mm/a。     

大跨度钢桁架模板在地下硐室中的研究与应用

以江苏省某人防坑道工程为背景,通过实际工程应用,结合安全性、经济性和可操作性综合比较,研究融合了钢模台车、承重脚手架、钢桁架和定型钢模等施工方法,形成硐室大跨度钢桁架模板施工技术。对该系统在地下硐室中的施工做了技术研究和应用探讨,重点介绍了工艺原理、模架设计及受力分析、工程应用等。该施工方法能够提高工效,节省成本,提高施工质量。     

变截面桩的力学性能及工程意义

通过对变截面桩的荷载传递性质及变形特性详细分析,指出其具有受力合理,沉降小等优点,并通过工程实例进行了验证。     

Late Mesozoic rift evolution and crustal extension in the central Songliao Basin,northeastern China: constraints from cross-section restoration and implications for lithospheric thinning

The Songliao Basin, the largest oil-producing basin in China, was the centre of late Mesozoic rifting and lithospheric thinning in northeastern China. However, the rifts are still poorly revealed due to a thick cover of subsidence successions. By structural interpretation and sequential restoration of cross-sections based on new 2D seismic data and well data, this study presents the structural style, basin evolution, and horizontal crustal extension of the central Songliao Basin. We have developed a novel method to retrieve the regional extension principal strains. The results enable an assignment of rifting into two episodes. The earlier episode (ca. 157–130 Ma) was dominated by distributed faulting of numerous planar normal faults trending NNE–SSW, NNW–SSE, or near NS, probably reflecting pre-existing basement fabrics; in contrast, the later episode (ca. 130–102 Ma) was controlled by localized extension along several major listric faults. Horizontal crustal extension during rifting is estimated to have been 11–28 km (10.6%–25.5%), with the long-term average rate varying from 0.20 to 0.51 mm yr^–1. Regional horizontal strains show a gradual evolution from biaxial extension at the beginning of rifting to WNW–ESE uniaxial stretching during the later rifting episode. Brittle crustal extension is interpreted to have been associated with vertical strain due to tectonic stretching, which is estimated to have contributed more in thinning the lower crust than the mantle lithosphere. Accordingly, a two-episode dynamic model is proposed to explain rifting in the Songliao Basin. We suggest that the earlier event was dominated by delamination of the thickened continental lithosphere, whereas the later event was probably controlled by regional crustal detachment due to slab subduction and stagnancy of the Izanagi lithospheric plate.     

Estimation of peak streamflows through channel geometry / Estimation de pics de débit fluviatiles à l'aide de la géométrie des cours d'eau

Abstract

Knowledge of peak discharge is essential for safe and economical planning and design of hydraulic structures. In India, as in most developing countries, the majority of river basins are either sparsely gauged or not gauged at all. The gauged records are also of short length (generally 15–30 years), therefore development of robust models is necessary for estimation of streamflows. Various studies reveal that flood estimation through channel geometry is an alternative method for ungauged catchments. It is appropriate for use where flow characteristics are poorly related to catchment area and other catchment characteristics. In the present study, stream geometry parameters for 42 river sites in central-south India were used; calibration equations were developed with data for 35 stations and tested on data for the remaining seven stations. The relationships developed between mean discharge and channel geometry parameters provide an alternative technique for estimation of mean annual channel discharge.     

长型大截面地下结构的横向自由振动方程

文中综合考虑了内阻尼、外阻尼、剪切变形、横截面转动惯性、轴力和地基模型参数的影响,推得了弹性地基梁的一般自由振动方程。由这一方程可以得到一系列特殊情况下地下结构的自由振动方程。这一方程不仅能从理论上扩展了Timoshenko粱理论,而且在后续的研究中,为研究上述因素对于地下结构的自由振动和强迫振动的影响奠定了理论基础。