地铁隧道保护区水平位移监测方法的研究

介绍一种在狭长的地铁隧道环境下基于边角后方交会的自由设站测量方法,阐述方法的原理,推导计算公式,结合在南京地铁隧道保护区监测水平位移测量的具体应用实例,分析方法的测量精度,证明方法在此类狭长条件下进行测量的可行性和可靠性。     

框架剪力墙结构模态静力非线性抗震分析方法研究

本文在模态pushover分析方法基础上推导建立了模态静力非线性分析方法,对一栋10层框架剪力墙结构进行了静力非线性分析,提出了目标位移求解的等效单自由度体系弹塑性时程分析迭代法,计算结果与相应时程分析结果进行了比较,表明两者吻合较好,验证了本文计算方法的有效性。另外,对同一结构,计算分析了在不同水平荷载模式下的静力非线性分析结果,比较不同荷载模式对计算结果的影响,为静力非线性分析方法的推广使用提供参考。     

Fishermen responses on marine protected areas in the Baltic cod fishery

Much of the research that concerns the impacts of management measures in the eastern Baltic cod fishery has focused on fish stock rather than understanding fishermen's attitudes towards regulations. Hence, there is little information available on fishermen's responses although they are the ones whom the regulations affect most profoundly. This study analyses the views of fishermen towards management measures with an emphasis on fishing closures (marine protected areas, MPAs). Swedish log-book data from 1996 to 2005 were used to describe MPA induced fishing effort displacements. Fishermen argued that MPAs have been inefficient in conservation of cod stock. The enlargement of Bornholm MPA in 2005 caused substantial effort displacement towards areas dominated by smaller sized fish. This contributed to the increased discarding of juvenile cod. Enlarged MPAs also intensified competition between different fleet segments and reallocated fishing areas. To reduce fishing mortality, fishermen suggested days-at-sea (effort) regulation and an effective landings control system for all fleets that exploit cod stocks in the Baltic Sea Main Basin. These measures would better motivate fishermen for mutual rule compliance, which is a prerequisite for a sustainable cod fishery.     

Theoretical aspects of cap-rock and fault seals for single- and two-phase hydrocarbon columns

Cap-rock seals can be divided genetically into those that fail by capillary leakage (membrane seals) and those whose capillary entry pressures are so high that seal failure preferentially occurs by fracturing and/or wedging open of faults (hydraulic seals). A given membrane seal can trap a larger oil column than gas column at shallow depths, but below a critical depth (interval), gas is more easily sealed than oil. This critical depth increases with lower API gravity, lower oil GOR and overpressured conditions (for the gas phase). These observations arise from a series of modelling studies of membrane sealing and can be conveniently represented using pressure/ depth (P/D) profiles through sealed hydrocarbon columns. P/D diagrams have been applied to the more complex situation of the membrane sealing of a gas cap underlain by an oil rim; at seal capacity, such a two-phase column will be always greater than if only oil or gas occurs below the seal.These conclusions contrast with those for hydraulic seals where the seal capacity to oil always exceeds that for gas. Moreover, a trapped two-phase column, at hydraulic seal capacity will be less than the maximum-allowed oil-only column, but more than the maximum gas-only column. Unlike membrane seals, hydraulic seal capacity should be directly related to cap-rock thickness, in addition to the magnitude of the minimum effective stress in the sealing layer and the degree of overpressure development in the sequence as a whole.Fault-related seals are effectively analogous to membrane cap-rocks which have been tilted to the angle of the fault plane. Consequently, all of the above conclusions derived for membrane cap-rocks apply to both sealing faults sensu stricto (fault plane itself seals) and juxtaposition faults (hydrocarbon trapped laterally against a juxtaposed sealing unit). The maximum-allowed two-phase column trapped by a sealing fault is greater than for equivalent oil-only and gas-only columns, but less than that predicted for a horizontal membrane cap-rock under similar conditions. Where a two-phase column is present on both sides of a sealing fault (which is at two-phase seal capacity), a deeper oil/water contact (OWC) in one fault block is associated with a deeper gas/oil contact (GOC) compared with the adjacent fault block. If the fault seal is discontinuous in the gas leg, however, the deeper OWC is accompanied by a shallower GOC, whereas a break in the fault seal in the oil leg results in a common OWC in both fault blocks, even though separate GOC's exist. Schematic P/D profiles are provided for each of the above situations from which a series of fundamental equations governing single- and two-phase cap-rock and fault seal capacities can be derived. These relationships may have significant implications for exploration prospect appraisal exercises where more meaningful estimates of differential seal capacities can be made.The membrane sealing theory developed herein assumes that all reservoirs and seals are water-wet and no hydrodynamic flow exists. The conclusions on membrane seal capacity place constraints on the migration efficiency of gas along low-permeabiligy paths at depth where fracturing, wedging open of faults and/or diffusion process may be more important. Contrary to previous assertions, it is speculated that leakage of hydrocarbons through membrane seals occurs in distinct pulses such that the seal is at or near the theoretically calculated seal capacity, once this has been initially attained.Finally, the developed seal theory and P/D profile concepts are applied to a series of development geological problems including the effects of differential depletion, and degree of aquifer support, on sealing fault leakage, and the evaluation of barriers to vertical cross-flow using RFT profiles through depleted reservoirs. It is shown that imbibition processes and dynamic effects related to active cross-flow across such barriers often preclude quantitative analysis and solution of these problems for which simulation studies are usually required.     

自由测站边角交会网在工程中的应用

鉴于自由测站边角交会网具有网形规则、可靠性高、多余观测数多和观测时无需对中等优点,提出将自由测站边角交会网应用于长大隧道洞内平面控制、基坑水平位移监测和有砟轨道CPⅢ平面网建网中。研究结果表明,将自由测站边角交会网应用于上述工程中都能在一定程度上克服传统方法的不足,提高测量效率和精度,值得推广使用。     

长江口沙波统计特征及输移规律

利用多波束测深系统对长江口南港、北槽、横沙通道和北港水下地貌进行测量,对沙波波高、波长、迎流倾角、背流倾角、水深和沉积物特征进行统计,并根据流速、沉积物粒径及水深估算其潮周期内净位移。结果表明:长江口沙波基本都为大型沙波,且沙波大小与其所在区域沉积物粒径呈正比关系;长江口各个区域沙波的对称性不同,涨、落潮优势流越明显,则沙波对称性越差,净位移越大;沙波对称性能反映此区域水动力强弱及潮周期内沙波净位移大小。     

双向八车道连拱隧道围岩力学参数反演分析

在采用双侧壁导坑法施工的双向八车道特大断面连拱隧道中,施工步繁多,临时支护设置的时间长,隧道全断面的变形量测只能在临时支护拆除后进行。由于全断面变形数据获取得较晚,故较难将其用于围岩力学参数的反演。将有限元计算和BP神经网络技术相结合,并在有限元计算过程中考虑实际的施工步,建立起所有临时支护拆除之前这一施工状态下导坑的变形量与围岩力学参数之间的非线性映射关系,并通过对应状态下实测的导坑变形值反演了围岩的力学参数。将反演的结果用于正分析验算,验证了该方法是可行的。     

A note on the useable dynamic range of accelerographs recording translation

Since the late 1970s, the dynamic range and resolution of strong motion digital recorders have leaped from 65 to 135 dB, opening new possibilities for advanced data processing and interpretation. One of these new possibilities is the calculation of permanent displacement of the ground or of structures, associated with faulting or with non-linear response. Proposals on how permanent displacements could be recovered from recorded strong motion have been published since 1976. The analysis in this paper concludes that permanent displacements of the ground and of structures in the near-field can be calculated provided all six components of strong motion (three translations and three rotations) have been recorded, and the records are corrected for transducer rotation, misalignment and cross-axis sensitivity.     

大山片麻岩地质特征及侵位机制研究

大山片麻岩的原财为奥长化岗石,呈不规则状侵入柳树河子片麻岩中,年龄２７亿年左右,太古代阜平运动晚期侵位的。侵位与当时区域上大规模的韧性剪切作用密切相关。由于剪切带各相关位置的位移量的差异,形成空间,给岩浆被动就位了有利场所,形成大山片麻岩古深成岩体。     

既有基坑延深开挖稳定性评价与支护方案确定

以北京市某特殊基坑工程为背景,采用FLAC3D软件,选用Mohr-Coulomb准则,对基坑在现有支护方案条件下进行延深开挖,计算分析桩锚支护体系的变形、受力情况。结果表明,基坑在现有支护方案条件下进行延深开挖将导致护坡桩抗弯性能不足、支护结构水平位移过大、锚固体系失效等问题,要保证基坑延深开挖后的安全稳定,必须对护坡桩增设支点,增加支护力。根据设计变更要求及施工现场实际条件,对多种加固支护方案进行比选,最终选用对护坡桩增设锚索的方案进行延深基坑的预加固。采用数值方法模拟分析上述加固方案后的基坑延深开挖力学行为,预测基坑及支护结构的变形情况,并与现场监测数据进行对比分析。结果表明,基坑延深开挖预加固支护方案合理有效,表明该方法对于类似工程的设计优化及现场施工具有重要的参考意义。