Kepingophyllidae壁部微细构造及其演化          下载免费PDF全文

张雄华 《地球科学》1995,20(1):43-46,T001

笔者用高倍光学显微镜和扫描电子显微镜，对Ｋｅｐｉｎｇｏｐｈｙｌｌｉｄａｅ壁部构造进行了详细的研究，从成因上将其划分为两类：泡沫板集聚型和隔壁始端集聚型，并对壁构造化进行了讨论。  相似文献   

填充墙与钢框架协同工作性能非线性分析   总被引：5，自引：2，他引：5  

戴绍斌  余欢  黄俊 《地震工程与工程振动》2005,25(3):24-28

在试验研究的基础上，运用ANSYS有限元中的接触单元建模，对加气混凝土填充墙钢框架的结构性能进行了研究，同时与纯钢框架结构在强度、刚度、以及延性等方面进行了对比分析，结果表明：填充墙与钢框架协同工作能够改善钢框架结构的受力性能和抗震能力，这为钢结构及其围护体系的研究与推广应用提供了一定的理论依据。  相似文献   

不同型式暗支撑短肢剪力墙抗震性能试验研究   总被引：6，自引：0，他引：6  

黄选明  曹万林  吕西林 《地震工程与工程振动》2005,25(3):60-66

本文选取短肢剪力墙结构体系中较为薄弱的抗震构件“一”形短肢剪力墙，采用不同的暗支撑型式进行了两个1／2缩尺的带暗支撑短肢剪力墙构件的低周反复荷载试验，比较分析了它们的承载力、刚度、延性、滞回特性、耗能能力及破坏机制，建立了其承载力计算模型与方法。计算结果与实测值符合较好。  相似文献   

半刚性连接钢管混凝土框架剪力墙结构的动力特性分析   总被引：1，自引：1，他引：1  

孙修礼  梁书亭  王群依  蒋永生  李玉莹 《地震工程与工程振动》2005,25(3):93-97

将钢管混凝土框架剪力墙结构作为连续弹性无限自由度结构，建立自由振动方程，分析了半刚性连接对结构自振周期和频率的影响，推导出半刚性连接框剪结构自振周期系数的计算公式。使用通用有限元程序ANSYS进行结构的模态分析，有限元分析结果和公式计算结果吻合良好。结果表明，半刚性连接使得结构自振周期增大，半刚性连接对高阶振型自振周期的影响很小。提出了地震区钢管混凝土框剪结构体系的设计建议，可供工程设计人员参考使用。  相似文献   

复合土钉支护结构中土钉设置的合理型式     

韩爱民  肖军华  梅国雄  戴加东 《水文地质工程地质》2005,32(4):97-99

采用非线性有限元方法,并借助正交试验原理,以支护最大水平位移为衡量目标,对复合土钉墙设计中的关键技术———土钉设置型式,包括倾角、间距、长度分布规律进行了合理性方面的研究。研究表明:将最长的土钉放于基坑中下部、保持较小的土钉间距和增大基坑中下部土钉倾角是复合土钉支护中土钉设置的最佳型式;在影响基坑变形敏感性程度上,土钉长度分布规律、间距、倾角依次降低。  相似文献   

Installation of a vertical slurry wall around an Italian quarry lake: complications arising and simulation of the effects on groundwater flow   总被引：1，自引：0，他引：1  

D. A. De Luca  M. Lasagna  A. Morelli di Popolo e Ticineto 《Environmental Geology》2007,53(1):177-189

Slurry walls are non-structural barriers that are constructed underground to impede groundwater flow or manage groundwater control problems. The study area is in the Piemonte plain (Italy), close to the River Po. Quarrying works carried out below the piezometric surface created two big quarry lakes. The local groundwater system is characterized by a lower semi-confined aquifer, which is overlain by a semi-permeable bed of clayey peat (aquitard) and an upper unconfined aquifer. Locally, the peat fades away and the granulometry of this horizon becomes silty sandy. A planned enlargement of the quarry will increase the size and depth of the quarry lakes. So the aquitard bed between the two aquifers will be damaged, creating a mixing rate of groundwater. Such a procedure would not be compatible with the presence of two municipal wells upstream from the quarries. Consequently, the installation of a vertical diaphragm (slurry wall) is recommended to separate the aquifers and to act as a filter for the groundwater flowing from the unconfined to the semi-confined aquifer. To predict the consequences caused by the installation of the vertical diaphragm separating the unconfined aquifer and the semi-confined one, a specifically adjusted finite-difference model was used. The model showed a maximum rising of the water table equal to 12 cm, just upstream of the diaphragm and for a distance of about 100 m, and a maximum lowering of 2 cm just downstream of the diaphragm. However, the slurry wall would not cause any change in the piezometric head in the area where there are municipal wells and, hence, will not have any negative effect on the functionality of the municipal wells. Moreover, the migration of water from the unconfined aquifer through the vertical diaphragm will stimulate a series of attenuation and auto-depuration processes of eventual contaminants. These processes are due to the higher crossing time that the groundwater flow takes to go through the vertical barrier (t _a = 96.5 days, whereas for the horizontal semi-permeable layer t _a = 9.6 days). So, the vertical diaphragm can be a resolutive element, representing a mediation and separation factor between the unconfined and the semi-confined aquifers along the border of the quarrying areas, and a protective barrier for the water quality of the quarry lake and the semi-confined aquifer.  相似文献   

Seismic Passive Earth Pressure Behind Non-vertical Retaining Wall Using Pseudo-dynamic Analysis   总被引：3，自引：0，他引：3  

Priyanka Ghosh 《Geotechnical and Geological Engineering》2007,25(6):693-703

This paper shows a detailed study on the seismic passive earth pressure behind a non-vertical cantilever retaining wall using pseudo-dynamic analysis. A planar failure surface has been considered behind the retaining wall. The effects of soil friction angle, wall inclination, wall friction angle, horizontal and vertical earthquake acceleration on the passive earth pressure have been explored. Unlike the Mononobe–Okabe method, which incorporates pseudo-static analysis, the present analysis predicts a nonlinear variation of passive earth pressure along the wall. The results have been thoroughly compared with the existing values in the literature.  相似文献   

Seismic rotational displacement of gravity walls by pseudo-dynamic method: Passive case   总被引：8，自引：0，他引：8  

Deepankar Choudhury  Sanjay Nimbalkar 《Soil Dynamics and Earthquake Engineering》2007,27(3):242-249

Prediction of the seismic rotational displacements of retaining wall under passive condition is an important aspect of design in earthquake prone region. In this paper, the pseudo-dynamic method is used to compute the rotational displacements of rigid retaining wall supporting cohesionless backfill under seismic loading for the passive earth pressure condition. The proposed method considers time, phase difference and effect of amplification in shear and primary waves propagating through both the backfill and the retaining wall. The influence of ground motion characteristics on rotational displacement of the wall is evaluated. Also the effects of variation of parameters like wall friction angle, soil friction angle, amplification factor, shear wave velocity, primary wave velocity, period of lateral shaking, horizontal and vertical seismic accelerations on the rotational displacements are studied. The rotational displacement of the wall increases substantially with increase in amplification of both shear and primary waves, time of input motion, period of lateral shaking and decreases with increase in soil friction angle, wall friction angle. The rotational displacements of the wall also increase when the effect of wall inertia is taken into account. Results are provided in graphical form.  相似文献   

隧道开挖过程中的渗透变形问题分析——结合南京地区工程实例   总被引：1，自引：0，他引：1  

许宝田  阎长虹  李小昭 《水文地质工程地质》2002,29(2):45-48

本文从水文地质条件、土体结构和力学性质等方面分析了南京地区土层中隧道开挖所引起的渗透变形问题。经研究认为可通过控制所构筑地下防渗墙深度、厚度及质量来防止渗透变形。实践证明该方法是有效的。  相似文献   

供水管井允许出水量的合理确定     

华解明  赵志忠 《中国煤田地质》2002,14(2):34-36

每一眼管井在井结构确定的条件下,有一个最大允许出水量,而盲目追求增大出水量,势必造成管井涌砂,过滤管腐蚀和堵塞的加剧。松散含水层供水管井允许出水量既要满足地下水允许开采量“宏观”定义要求,从供水管井使用寿命考虑又要满足管井两个流速参数:井壁允许进水流速和滤管允许进水流速。本文给出了管井允许出水量确定方法和计算框图,并以实例说明之,在具体应用时某些细节也予以了说明。  相似文献