基坑防渗体局部失效渗流场变化特征     

李守德  于达 《探矿工程》2005,32(10):2-5

采用三维有限元方法分析了基坑开挖工程在防渗体出现局部失效情况下，引起渗流在失效部位的集中及渗流场空间状况。提出了以一维通道嵌入三维块体的方法模拟管涌发展过程及渗流场变化特征。讨论了管涌通道渗透性对基坑管涌发展规律的影响。  相似文献   

Analysis of soil nail walls performance - Case study     

Emad Zolqadr  Seyed Shahaboddin Yasrobi  Mohammad Norouz Olyaei 《Geomechanics and Geoengineering》2016,11(1):1-12

This study surveys the performance of temporary soil nail walls with a maximum height of 29.3 m in the Yas project, located in Tehran. Some numerical models, with various modelling approaches, were developed using finite element software and the proper modelling approaches were specified and verified.The modelling results were analysed and compared with the in situ monitored data. The results demonstrate the model’s horizontal deformations are generally greater than the in situ monitored values. To decrease the differences between models and monitored results, the effect of variations of the soil parameters had been surveyed and the limits of needed variations were specified.  相似文献   

Effect of Groundwater Fluctuations on Pore Pressures and Earth Pressures on Coastal Excavation Retaining Walls     

Lisha Zhang  Kanghe Xie  Dazhong Huang 《Marine Georesources & Geotechnology》2016,34(8):770-781

Pore water and earth pressures acting on retaining structures are investigated using an efficient coastal double-layered excavation model to determine offshore excavation responses to groundwater fluctuations outside foundation pits. Total pore water pressure includes excess pore water pressure (due to groundwater fluctuations) and steady pore water pressure (due to steady seepage) determined using one-dimensional consolidation theory of double-layered soil and one-dimensional steady-state flow theory, respectively. Rankine's active and passive earth pressures are obtained from pore water pressure. This method is applicable to arbitrary groundwater fluctuation conditions. How physical parameters affect pore water pressure is numerically investigated using examples, demonstrating the method's practicality for calculating pore water and earth pressures.  相似文献   

Helical probe tests in residual soils of the Appalachian Piedmont     

Shehab S. Agaiby  Zhongkun Ouyang  Paul W. Mayne 《Geomechanics and Geoengineering》2018,13(3):217-225

Helical probe tests (HPT) are a quick and economical means for manual field testing of soils to depths of 1.5 m with readings taken at 0.15-m intervals in only 10 min. The equipment is lightweight (only 2 kg) and thus amenable to deploy on initial site reconnaissance explorations, shallow pavement projects, earth retention walls, and/or compaction of fills. Although suitable for use in a variety of geomaterials: sands, silts, clays, and mixed soils, the specific application to residual fine sandy silts and silty fine sands of the Appalachian Piedmont and Blue Ridge geologic provinces is shown here. Existing relationships for converting the measured HPT torque reading to equivalent cone penetration testing (CPT) tip resistances are reviewed, as well as other trends.  相似文献   

长江漫滩区深大异形基坑施工对紧邻特大型桥梁影响及变形控制研究     

史建升  徐源  李慧  阎长虹  侯珏  俞良晨  赵华新  崔王洪  徐成华  刘刚 《地质论评》2024,70(1):2024010005-2024010005

随着地下空间资源的开发利用,越来越多深基坑呈现出开挖深、规模大、形状不规则等特点,其支护结构设计复杂,施工难度大,具有明显的空间效应。本文以南京地铁某基坑工程为例,分析基坑施工对邻近桥梁的影响。其场区位于长江下游漫滩相二元结构地层分布地段,上部软土层厚度大,下部承压含水层地下水位高、水量丰富,地质条件复杂,该基坑为典型的深大异形基坑,距离某大桥的双曲拱引桥仅为7. 2 m,由于之前桥梁已遭受其他地下工程施工产生的较大变形,所以后续工程对其影响变形控制要求极高。为此,该车站基坑支护结构设计基于地下空间实际功能采用设置分隔墙分区开挖及MJS超深工法墙综合变形控制方案。本文通过有限元数值模拟计算,开展复杂环境下基坑开挖引起的围护结构及桥梁桩基的变形预测分析,计算结果显示,该深大狭长异形基坑开挖对邻近桥梁沉降变形影响显著,通过设置分隔墙分区开挖及MJS工法墙进行变形控制,能够较好地控制基坑的空间效应,减少“长边效应”、“异形效应”等对桥梁沉降变形的影响。通过现场基坑开挖过程实际监测结果,验证这一综合变形控制方案的可行性。该研究成果对于类似复杂地质条件下深大狭长异形基坑的支护及施工设计具有很好的借鉴意义。  相似文献   

Discontinuous behaviour near excavations in a bedded salt formation     

J. C. Stormont 《Geotechnical and Geological Engineering》1990,8(1):35-56

Summary Discontinuous behaviour is being observed and measured in the vicinity of excavations constructed in a bedded salt formation 650 m below ground surface for the Waste Isolation Pilot Plant (WIPP) Facility. The 2 m thick salt layer in the immediate roof acts as a beam, shearing along a thin overlying anhydrite/clay seam. Vertical separations between the immediate roof layer and the overlying strata are often observed at the anhydrite/clay seam above the centre of excavations of larger span (11 m). The floor of the excavations is comprised of a 1 m thick salt layer underlain by a 1 m thick predominately anhydrite layer (referred to as MB139). Fractures in MB139 develop beneath most excavations, with increased fracture frequency with drift span and age. In the excavations of larger span (11 m), MB139 eventually debonds along the underlying clay layer. The salt layer overlying MB139 develops both shear and tension failure. In a few locations below excavations of large span, continuous fracture systems are developing from rib to rib through MB139 and the overlying salt. In the ribs, there is limited fracturing within the first metre of most larger excavations. Vertical fractures develop in pillars at most intersections. The discontinuous behaviour is qualitatively consistent with analyses of the formation behaving as a layered medium (elastic beam analysis) and limited tensile and compressive failure of the rock salt. The significance of the discontinuous behaviour is that it can dominate the effective fluid transport properties of the formation near the excavation, and therefore requires consideration in the design of repository seals. Discontinuous behaviour must be monitored and is an important factor in the maintenance programme designed to assure a safe underground environment.  相似文献   

黄河上游某坝址平硐开挖后岩体变异时间效应规律分析     

丁梧秀 《地质灾害与环境保护》1995,6(2):37-41,53

工程岩体开挖后改变了原来的赋存条件与环境，沿硐壁岩体表面卸荷由于应力的重新调整，表现在波速上升的下降，即岩体性状发生变异。随着时间的增加，变异程度加大，而变异的速率却逐年下降，文章根据黄河上游某水电工程坝址平硐壁不同时间（几个同点位）弹性波速测量结果，拟合了波速年下降率Ｄ（％）与开挖一测定时间间隔Ｎ（ａ）的函数关系。并根据这种关系进行岩体波速的反算，求得了开挖时岩体的波速值，反映其本来的性状，对一  相似文献   

浅析山区高等级公路中的边坡工程岩体   总被引：6，自引：1，他引：6  

晏鄂川  王晋等 《地球科学》2001,26(4):347-351

随着山区高等级公路建设的飞速发展，各类边坡工程岩体问题也日益增多。从卸荷岩体力学的基本观点入手，探讨了边坡工程岩体的变形破坏特性、稳定性评价方法以及开挖设计理论。研究表明，边坡工程岩体的变形破坏特性完全符合卸荷岩体力学行为，不同于常规的加载岩体行为；边坡工程岩体的稳定性分析计算中必须重视水力学因素和卸荷作用的影响，并得到了有意义的表达式；边坡工程岩体的开挖设计应在充分认识其工程力学性状的基础上，针对边坡岩体地质特性，结合已有各类稳定边坡的资料，进行既经济又可靠的优化设计。  相似文献   

基坑变形影响因素与有限元数值模拟   总被引：5，自引：0，他引：5  

李云安  葛修润  张鸿昌 《岩土工程技术》2001,(2):63-68,85

基坑变形影响因素是其变形控制的重要内容之一，在自制深基坑工程变形控制优化设计及其有限元数值模拟系统(SDCDEFEM)的基础上，重点对影响基坑变形的各因素进行了有限元数值模拟分析，并对实测和计算的基坑周边最大沉降、支护结构最大水平位移和坑底最大隆起及其位置进行了统计分析，得出了简明估算基坑最大变形及其位置的统计关系式，提出了经济有效的变形控制对策。  相似文献   

关于吉林地区挖孔桩设计问题的探讨     

李向群  袁铁铮 《吉林大学学报(地球科学版)》2001,31(4):372-375

探讨了在吉林地区高层建筑中有关桩基规范执行及设计施工过程中常见的问题。通过对不同直径的桩端进入持力层深度的对比 ,明确 2d与 4d的对比要求 ,即持力层厚度的保证比进入持力层深度更重要。针对通长配筋“一通到底”的设计给施工带来的不便及浪费提出了新的建议。通过实践给出“α”角的建议值 ,既能减小扩大桩头斜面上受到卸荷后侧土压力 ,又可减少施工时的坍方。最后对降水及护壁提出了结合实际地质情况的 4种方法。  相似文献