Study on Longitudinal Deformation Profile of Rock Mass in a Subsea Tunnel

During tunnel excavation, the deformation of surrounding rock due to the unloading of rock mass will vary with time. However, the measured displacement of surrounding rock is only a part of the actual longitudinal deformation profile. There is a need to analyze the longitudinal deformation profile to identify the deformation state and evaluate the stability of surrounding rock mass. In the present article, the variation of pre-deformation of surrounding rock due to excavation was analyzed, and the release coefficient was obtained from the measured results. For the Qingdao subsea tunnel, the measured crown settlement of surrounding rock was analyzed using the regression analysis method, and the longitudinal deformation profile of rock mass was simulated using the numerical calculation method. Moreover, based on the conditions of the subsea tunnel, a solid-fluid coupling model test was carried out to check the reliability of the numerical calculation results. The results of the model test were consistent with the numerical calculation results.     

The Effect of Concrete Deformation on Displacement of an Axially Loaded Drilled Shaft

This article presents the settlement of drilled shafts resulting from their structural deformations. Although drilled shafts are widely used as foundations for settlement-sensitive structures such as bridges and high-rise buildings, the structural deformations of drilled shafts are not typically taken into account in the design process. However, if unexpected structural deformations of drilled shafts cause additional settlement to the foundation, the serviceability of the superstructure can be jeopardized. Unfortunately, very few research efforts have been made to quantify the structural deformation of drilled shafts; this needs to be addressed to accurately predict the settlement of drilled shafts. In this study, we investigate the effect of structural deformation on displacement of axially loaded drilled shafts. Finite element analyses were performed to quantify the structural deformation of drilled shafts. The analysis results indicated that the structural deformation of drilled shafts could be quite significant for long drilled shafts. The main factors that affected the structural deformation of drilled shafts were found to be pile length, the material properties of drilled shafts, and the relative humidity of surrounding soil. An approximate equation is proposed to estimate the long-term deformation of drilled shafts.     

Neotectonics of the Kharaulakh sector of the Laptev Shelf

Seismotectonic deformation and crustal stress pattern have been studied comprehensively in major seismogenic structures of the Kharaulakh sector of the Verkhoyansk fold system and adjacent parts of the Chersky seismotectonic zone. The study focuses on neotectonic structures, deep structure, and systems of active faults, as well as tectonic stress fields inferred by tectonophysical analysis of Late Cenozoic faults and folds. The results, along with geological and geophysical data, reveal main strain directions and structural patterns of crustal stress and strain in the Arctic segment of the Eurasia-North America plate boundary. The area is a junction of mid-ocean and continental structures evolving in a mixed setting of extension, compression, and their various combinations. The rotation pole of the two plates is presumably located near Buor-Khaya Bay. In this case, extension is expected to act currently upon the neotectonic structures north of the bay and compression to control those in the south and southeast. This inference is consistent with the identified zoning of stress and strain in the Kharaulakh sector.     

内蒙古1∶5万乌音呼日勒庙等四幅区域地质矿产调查新进展

内蒙古1∶5万乌音呼日勒庙等四幅区域地质矿产调查项目取得的新进展及主要成果为: 根据岩石组合、动植物化石及同位素年龄等,重新厘定、划分了16个岩石地层填图单位,在多个组段沉积岩层位中首次发现丰富的动、植物化石,建立了各地层年代学格架; 将侵入岩重新解体划分为4个填图单元,并建立了侵入岩年代学格架; 新发现1处规模较大的韧性变形带,主要为逆—左行走滑韧性断层,时代归属于中三叠世末期,为额尔古纳河—阿龙山NE向韧性变形域的南部延伸; 新发现矿(化)点20处,其中金属矿点3处,金属矿化点6处,非金属矿点9处,非金属矿化点2处; 总结了该区成矿规律,圈定了成矿远景区及找矿靶区。     

孔隙性砂岩中单条变形带与簇状变形带的特征与区别——以远安地堑上白垩统红花套组中变形带为例

孔隙性砂岩中的变形带研究近年来取得长足进展,但有关单条变形带与簇状变形带如何区分和界定仍是一个较模糊的问题。本文以远安地堑上白垩统红花套组高孔砂岩中发育的剪切增强压实带和压实剪切带为例,对单条及簇状变形带的特征和区别做出系统分析。研究表明,虽然单条变形带的长度、宽度、错断位移、凸起高度等均明显小于簇状变形带,但是不同运动学成因的变形带宏观特征、微观结构不同,因此不能单纯以规模大小区分二者,需要结合带密度将簇状变形带与变形带列、网格构造等相区分,还需要结合其微观结构特征进行准确鉴定。单条及簇状剪切增强压实带特征类似,均不具核心碎裂带,颗粒主要为中等破碎,多表现为多个不连续分布的碎裂核。簇状剪切增强压实带内部的非均质性更强。单条压实剪切带具有核心碎裂带,依剪切力大小不同,其核心碎裂带内颗粒粉碎程度及边缘过渡带宽度不同,常伴随微小剪切缝痕迹。簇状压实剪切带在镜下可清晰识别出不同的核心碎裂带、带间区域及微小剪切缝,可见S—C组构和断续分布的滑动面。单条及簇状变形带的发育会不同程度地改变储层的物性并可能会对油气运移和开采产生影响。     

Deformation patterns of upper Quaternary strata and their relation to active tectonics,Po Basin,Italy

Despite increased application of subsurface datasets below the limits of seismic resolution, reconstructing near‐surface deformation of shallow key stratigraphic markers beneath modern alluvial and coastal plains through sediment core analysis has received little attention. Highly resolved stratigraphy of Upper Pleistocene to Holocene (Marine Isotope Stage 5e to Marine Isotope Stage 1) alluvial, deltaic and coastal depositional systems across the southern Po Plain, down to 150 m depth, provides an unambiguous documentation on the deformation of previously flat‐lying strata that goes back in time beyond the limits of morphological, historical and palaeoseismic records. Five prominent key horizons, accurately selected on the basis of their sedimentological characteristics and typified for their fossil content, were used as highly effective stratigraphic markers (M1 to M5) that can be tracked for tens of kilometres across the basin. A facies‐controlled approach tied to a robust chronology (102 radiocarbon dates) reveals considerable deformation of laterally extensive nearshore (M1), continental (M2 and M3) and lagoon (M4 and M5) marker beds originally deposited in a horizontal position (M1, M4 and M5). The areas where antiformal geometries are best observed are remarkably coincident with the axes of buried ramp anticlines, across which new seismic images reveal substantially warped stratal geometries of Lower Pleistocene strata. The striking spatial coincidence of fold crests with the epicentres of historic and instrumental seismicity suggests that deformation of marker beds M1 to M5 might reflect, in part at least, syntectonically generated relief and, thus, active tectonism. Precise identification and lateral tracing of chronologically constrained stratigraphic markers in the ¹⁴C time window through combined sedimentological and palaeoecological data may delineate late Quaternary subsurface stratigraphic architecture at an unprecedented level of detail, outlining cryptic stratal geometries at the sub‐seismic scale. This approach is highly reproducible in tectonically active Quaternary depositional systems and can help to assess patterns of active deformation in the subsurface of modern alluvial and coastal plains worldwide.     

InSAR技术在多年冻土区形变监测的应用

作为大地测量的一种新兴空间技术,合成孔径雷达干涉（synthetic aperture radar interferometry, InSAR）具有全天时、高精度、大范围和速度快的优点,逐渐被应用于多年冻土区地表形变监测中。通过综述多年冻土形变原理及InSAR监测多年冻土形变的应用实例,研究表明：在气候变暖的背景下,多年冻土区地表年际形变以下沉为主,多年冻土上限附近地下冰含量的大小是影响年际形变量的主要因素;活动层内土壤含水量影响着地表季节形变量的大小,不同类型多年冻土区的地表年际形变量和季节形变量存在着较大的差异。研究还表明,不同波长的SAR产品在不同类型多年冻土区的适用性不同,下垫面特征对利用InSAR获取地表形变量有较大影响,L波段的SAR数据在植被覆盖度较好的区域有更好的效果。由于InSAR的失相干问题,加之目前还缺少长时间、多类型、高频率的实测形变结果作为验证和标校数据,获取准确且连续的大范围形变数据较为困难。针对目前寒区研究需求,布设野外长期观测站点,建立适用于不同多年冻土区的地表形变反演算法,构建具有较高精度和较高时空分辨率的地表形变数据集具有重要的实践和科学意义。     

节理分布空间变异的地下洞室稳定性概率分析

以岩土材料力学参数空间变异性的"点估计-有限元"分析方法为基础,结合节理分析时自身存在几何模型、网格划分等特性,扩展了该方法在节理分布空间变异性分析方面的适用性,明确了具体的研究步骤与方法。以某抽水蓄能水电站为例,通过分析节理空间变异性对围岩变形与塑性区的影响,验证了扩展后该方法的准确性和合理性。对工程案例开挖揭露的1400余条节理进行概率统计,建立了节理空间变异性的有限元分析模型;采用扩展后的概率分析方法,研究了节理分布对地下洞室群围岩开挖稳定性的影响。研究结果表明:(1)对比概率分析得到的围岩变形概率分布与现场监测结果,发现剔除变形异常点后监测变形量值大部分位于得到的位移概率分布范围内,说明节理的空间变异性是导致监测变形波动的主要影响因素;(2)围岩变形概率分布的标准差能有效识别出围岩开挖变形受节理空间变异性的影响程度,对于所给出的案例依次为:机窝>边墙>顶拱;(3)围岩塑性区的概率分区能合理判断地下洞室群开挖时受节理影响较大的区域和范围,为工程施工的支护设计提供依据。     

成层软土地基预固结处理后桩基水平承载力估算方法

目前通过对软土地基预加固处理来提高桩基水平承载力已被工程界认可,但如何在工程前期设计过程中估算软土地基预处理后桩基水平承载力提高值仍是技术难点。基于此,参考Bowles[1]的地基土水平抗力计算式,同时考虑成层软土地基预排水固结处理影响,通过数学推导,推求出根据原状软土室内土工试验抗剪强度指标及预加固处理时间,估算软土地基预处理后桩基水平承载力提高值的实用计算方法。考虑桩侧土弹塑性屈服影响,推导出成层软土中水平受荷桩弹塑性解析解及塑性区深度的计算式,给出了桩顶水平位移、桩身最大弯矩的无量纲计算式及相关计算源代码。依托于浙江省某水闸桩基工程案例,根据提出的计算方法对桩基水平承载力、桩顶水平位移及桩身最大弯矩等性状进行预估计算,并与地基预处理前、后现场试桩检测值进行验证对比,认为桩基水平承载力、桩顶水平位移及桩身最大弯矩等预估计算成果与工程现场试桩的检测值较接近,对类似工程设计具有较好的参考价值。     

非饱和土中水平入渗方程显式求解

在求解非饱和态土中水分入渗问题时,水力函数是体积含水率或者吸力的函数,致使其控制方程呈现出强非线性的特征,进而使得其求解变得十分困难。基于水分在土体介质中流动耗时取极值路径的选择这一假定,引入时间泛函,基于变分法原理将水平入渗问题转化为泛函极值问题。通过求解Euler–Lagrange方程,结合边界条件,得到非线性瞬态水平入渗问题的显式解析解。结合Brooks-Corey型水力函数,显式地求解出该类型非饱和态土的体积含水率发展分布规律。通过计算4种不同类型土体的水平入渗规律,将求解结果与已有结果以及数值结果进行对比,验证了该方法的有效性。结果表明:体积含水率分布与位置距离和湿润峰距离比值呈幂函数关系,指数取决于土-水特征曲线的形状参数;初始条件与边界条件会对体积含水率分布造成不同程度的影响。