Cement-improved soil reinforcement has emerged as an effective technique for enhancing the bearing capacity of offshore wind turbine foundations. This study employs 3D finite element simulation to evaluate the dynamic behaviors of an offshore wind turbine (OWT) supported by a monopile reinforced with cement soil under combined wind, wave, and seismic forces. By comparing behaviors with those of unreinforced monopiles, the seismic performance improvement due to cement soil reinforcement is evaluated. The results show that the natural frequencies of the OWT structural system increase after reinforcement, with higher-order modes exhibiting more pronounced frequency increments. Under wind-wave loading, the lateral deflection at the tower apex in the reinforced case (with a reinforcement zone of Dc = 3D and Lc = 1D) decreases by approximately 30% compared to the unreinforced case. Under seismic loading alone, the same reinforced configuration reduces the maximum value of lateral displacement, cumulative settlement, and rotation of the pile foundation by about 15%, 20%, and 30%, respectively. The coupled effects of seismic, wind, and wave loading amplifies the dynamic response of the foundation. Strengthening the shallow soft soil surrounding the pile treated with cementimproved material significantly improves the load-bearing performance and stiffness of the foundation system, thus effectively mitigating the dynamic behavior characteristics under multi-hazard conditions.

The well-developed coal electricity generation and coal chemical industries have led to huge carbon dioxide (CO2) emissions in the northeastern Ordos Basin. The geological storage of CO2 in saline aquifers is an effective backup way to achieve carbon neutrality. In this case, the potential of saline aquifers for CO2 storage serves as a critical basis for subsequent geological storage project. This study calculated the technical control capacities of CO2 of the saline aquifers in the fifth member of the Shiqianfeng Formation (the Qian-5 member) based on the statistical analysis of the logging and the drilling and core data from more than 200 wells in the northeastern Ordos Basin, as well as the sedimentary facies, formation lithology, and saline aquifer development patterns of the Qian-5 member. The results show that (1) the reservoirs of saline aquifers in the Qian-5 member, which comprise distributary channel sand bodies of deltaic plains, feature low porosities and permeabilities; (2) The study area hosts three NNE-directed saline aquifer zones, where saline aquifers generally have a single-layer thickness of 3-8 m and a cumulative thickness of 8-24 m; (3) The saline aquifers of the Qian-5 member have a total technical control capacity of CO2 of 119.25 x 106 t. With the largest scale and the highest technical control capacity (accounting for 61% of the total technical control capacity), the Jinjie-Yulin saline aquifer zone is an important prospect area for the geological storage of CO2 in the saline aquifers of the Qian-5 member in the study area. (c) 2024 China Geology Editorial Office.

Tripod suction bucket foundation is increasingly used to support offshore wind turbines (OWTs) due to its convenient and low-cost installation and high overturning resistance. However, the seismic response characteristics of OWTs of tripod bucket foundations in sands is not well covered in the literature. Therefore, this study investigates the response of tripod bucket foundations installed in sands and subjected to seismic loads employing advanced three-dimensional finite difference analysis. The variation of pore pressure around suction bucket is evaluated, and the failure mechanism of the tripod bucket foundation in sands is revealed. In addition, the displacement response of the tower, and the acceleration amplification effect of the OWT system are elucidated. It is found that the earthquake magnitude, and sand relative density and liquefaction greatly affect the foundation seismic behavior. The results revealed that the overall rotation of the tripod bucket foundation is primarily due to progressively increasing differential vertical settlement between the foundation sides of ‘single bucket’ and ‘double bucket’ associated with loading direction. It was also found that the sand liquefaction under strong shaking may lead to excessive rotation of the foundation that exceeds the service limit state. The findings from this study can provide guidance for the design of OWT tripod bucket foundations in sands.

Tripod pile foundation is pursued as an efficient foundation system for offshore wind turbines (OWTs) installed in deeper waters (20–50m). In this application, the foundations would be subjected to dynamic loads including due to wind, waves, and earthquakes. This paper presents a numerical method for analyzing the dynamic responses of tripod pile foundation installed in clay based on a simplified bounding surface model to capture the clay stiffness degradation. Their behaviors under lateral monotonic, cyclic and seismic loads were investigated, and their bearing mechanism was analyzed. The results revealed that the loading direction significantly affects the ultimate bearing capacity of tripod pile foundation as the foundation capacity results from either a Pile A in tension and a Pile B in compression or vice versa. The evolution of axial force, bending moment and lateral displacement profiles of the Pile A and Pile B with the number of cycles exhibit different characteristics under lateral one-way and two-way cyclic loading. The foundation experiences cumulative rotation angles toward the Pile A side under seismic load due to the lower vertical bearing capacity of the Pile A compared to the Pile B. The tower top experiences the maximum lateral displacement and rotation angle, and the top of tripod support experiences the maximum bending moment. These findings should be considered in the design of OWT tripod pile foundations.

文章针对天津滨海K0固结饱和软黏土,开展轴向及侧向耦合循环加载真三轴试验.重点探讨了循环中主应力系数及循环应力水平对软黏土动应力应变响应的影响.试验结果表明:同一循环应力水平,循环中主应力系数越大,累积永久大主应变越小,中主应力的增大对大主应变的发展有抑制作用;循环中主应力系数在0.4～0.6,存在某一临界值,其为中主应变发生正负反向的临界点.同一中主应力系数,循环应力水平越高,土样最终累积永久主应变越大;循环应力水平在0.4～0.46,存在某一临界值,其为土样循环振稳及失稳的临界点.在大主应力方向,循环中主应力系数越小,土体刚度弱化越显著;在中主应力方向,刚度弱化程度随中主应力系数的变化并非单调.循环应力水平越大,土体刚度弱化越显著.利用广义剪应变表征三维复杂应力状态下土单元的应变水平,建议了能够预测任意给定循环中主应力系数、循环应力水平及循环次数下累积永久广义剪应变的指数函数表达式.研究成果以期为波浪、交通等复杂动荷载作用下软黏土地基的稳定性分析及变形计算提供试验依据.

基于ABAQUS软件平台,针对浅埋及深埋两种情况,采用数值模拟手段研究了正常固结饱和黏土中倾斜平板锚的抗拔承载力,分析了不同土重条件及锚土接触条件对倾斜锚板抗拔承载特性的影响,揭示了不同工况下倾斜锚板周围土体的流动机制,阐明了埋置深度、土重条件及锚土接触条件对锚板破坏机制的影响.研究结果表明:"锚土分离"条件下,承载力系数随倾斜角度增大逐渐增大,这主要是由于土体剪切破坏面随倾斜角度的增大逐渐增大所致;"锚土黏结"条件下承载力系数随倾斜角度增大逐渐减小,这主要是由于土体的剪切破坏面随倾斜角度增大逐渐减小所致;无论"锚土分离"还是"锚土黏结",浅埋条件下倾斜角度对承载力的影响均要大于深埋条件.建议了能够预测"锚土黏结"条件下倾斜锚板承载力的表达式,可为正常固结黏土中平板锚的工程设计提供参考.

工程地质学是实践性很强的一门课程,文章以本校土木工程专业工程地质实践教学为例,在根据目前实践教学资源、时间及经费安排的基础上,提出了一系列的解决方案以及提出把电子教学的方式引入到实践教学中,能极大地调动学生兴趣和提升学习动力,提高学生的探索能力和增强学生的创新意识.

The most serious earth fissure disasters in China occur in the Fenwei basin. Since the late 1950s, earth fissure disasters have widely occurred in the Weihe, Yuncheng, Linfen, Taiyuan, and Datong sub-basins in the Fenwei basin, and such disaster has increased progressively in recent years. The current paper summarizes the characteristics of earth fissures in the Fenwei basin. Earth fissures usually occur in an extensional faulted basin, along an active fault zone, and within an area of land subsidence. Earth fissures often have a similar trend, with many branches that intermittently appear along their strike. The main and secondary earth fissures at a shallow depth form rupture belts of different widths, but they merge into a single shear belt and stay connected with the underlying active fault. The throw of two blocks increases with depth along a sedimentary fault. Earth fissures usually show the characteristic of three-dimensional movement. Vertical dislocation is the primary aspect of earth fissure movement. The horizontal tension is smaller and the horizontal twist is the smallest, which is consistent with the movement pattern of underlying active faults. Earth fissures have exhibited activity three or four times since the late Pleistocene. In the past half-century, earth fissures formed during four or five periods of peak activity were influenced strongly by groundwater fluctuation. Our research also indicates that cluster formation of earth fissures is polygenetic and results from a combination of tectonic and human activities. Earth fissures are driven by deep tectonic motions beneath the basin and are controlled by the local tectonic stress of the local fault zones. One of the most important factors contributing to earth fissure formation is groundwater overexploitation. This paper provides a scientific basis for proposed administrative means, mitigation measures and engineering solutions in the field of engineering geology.

以北京华都中心深基坑开挖引起昆仑公寓的沉降和倾斜观测为例,详细介绍了采用GNSS(global navigation satellite system)精密单点定位技术(precise point positioning,PPP)对高层建筑的倾斜和沉降进行长期监测的方法.该方法包括以下4步:①采用PPP解算GNSS天线在全球参考框架(IGS08)中的地心地固(Earth-centered,Earth-fixed,ECEF)坐标(ECEF-XYZ);②将相对于全球参考框架的ECEF-XYZ坐标转换到一个区域性稳定参考框架,即华北参考框架(NChina16)中;③在华北参考框架中将地心坐标转换为站心直角坐标(东西、南北和垂直3方向);④用华北地区季节性地面变形模型校正站心坐标位移时程,恢复建筑结构的真实位移(倾斜和沉降).研究表明,在华北地区,PPP位移测量精度在水平方向上能够达到2～3 mm,在竖直方向上能够达到6～9 mm(24 h连续观测).通过将PPP、NChina16与华北季节性地面变形模型相结合,可以实现对华北地区高层建筑和其他大型基础工程的准实时和长期静态变形监测,监测精度可达到毫米级.

In this study, 5002 ground fissures in more than 1500 localities across 22 provinces in China are investigated and mapped to reveal their spatial distribution. The distribution of these ground fissures in China exhibits six regular patterns-assemblages in North China, syngenesis in extensional basins, clustering along fault zones, distributing along geomorphic boundaries, developed on the edge of subsidence areas, and clustering in large and mediumsized cities. Combined with regional GPS, numerical simulations, physical model test and In-SAR monitoring, the generative processes of ground fissures are analyzed and discussed in relationship to four mechanisms: (1) deep dynamic tectonism controls on the location of ground fissures, (2) intracontinental dynamic tectonism resulting in ground fissure assemblages, (3) fault stress inducing formation of ground fissures, and (4) groundwater overmining resulting in the reactivation and expansion of ground fissures. The geological environment is thus responsible for the establishment and appearance of ground fissure. More importantly, ground fissure propagation in China is the result of the synergistic effects of internal geological dynamic (including in deep tectonism, intracontinental tectoniim, and fault movement) coupled with anthropomorphic stress. This genetic model can be summarized as one that is tectonically controlled, stress -driven, and affected by regional hydrodynamic.

The Long Point Fault is one of the most active urban faults in Houston, Texas, which belong to a complex system of normal growth faults along the Texas Gulf Coast. To assess the activity of the Long Point Fault, a GPS array with 12 permanent stations was installed along the two sides of the 16-km-long fault scarp in 2013. GPS datasets were processed with the Precise Point Positioning (PPP) and Double-Difference (DD) methods. The daily PPP solutions with respect to the International Global Navigation Satellite System (GNSS) Reference Frame 2014 (IGS14) were converted to the Stable Houston Reference Frame (Houston16). The six-year continuous GPS observations indicate that the Long Point Fault is currently inactive, with the rates of down-dip-slip and along-strike-slip being below 1 mm/year. The Long Point Fault area is experiencing moderate subsidence varying from 5 to 11 mm/year and a coherent horizontal movement towards the northwest at a rate of approximately 2 to 4 mm/year. The horizontal movement is induced by the subsidence bowl that has been developing since the 1980s in the Jersey Village area. Current surficial damages in the Long Point Fault area are more likely caused by ongoing uneven subsidence and its induced horizontal strains, as well as the significant seasonal ground deformation, rather than deep-seated or tectonic-controlled fault movements. The results from this study suggest a cause-and-effect relationship between groundwater withdrawals and local faulting, which is pertinent to plans for future urban development, use of groundwater resources, and minimization of urban geological hazards.

Terrestrial laser scanning (TLS) has become a powerful data acquisition technique for high-resolution high-accuracy topographic and morphological studies. Conventional static TLS surveys require setting up numerous reflectors (tie points) in the field for point clouds registration and georeferencing. To reduce surveying time and simplify field operational tasks, we have developed a rapid TLS surveying method that requires only one reflector in the field. The method allows direct georeferencing of point clouds from individual scans to an East–North–Height (ENH) coordinate system tied to a stable geodetic reference frame. TLS datasets collected at a segment of the beach–dune–wetland area in Freeport, Texas, USA are used to evaluate the performance of the rapid surveying method by comparing with kinematic GPS measurements. The rapid surveying method uses two GPS units mounted on the scanner and a reflector for calculating the northing angle of the scanner’s own coordinate system (SOCS). The Online Positioning User Service (OPUS) is recommended for GPS data processing. According to this study, OPUS Rapid-Static (OPUS-RS) solutions retain 1–2 cm root mean square (RMS) accuracy in the horizontal directions and 2–3 cm accuracy in the vertical direction for static observational sessions of approximately 30 min in the coastal region of Texas, USA. The rapid TLS surveys can achieve an elevation accuracy (RMS) of approximately 3–5 cm for georeferenced points and 2–3 cm for digital elevation models (DEMs). The elevation errors superimposed into the TLS surveying points roughly fit a normal distribution. The proposed TLS surveying method is particularly useful for morphological mapping over time in coastal regions, where strong wind and soft sand prohibit reflectors from remaining strictly stable for a long period. The theories and results presented in this paper are beneficial to researchers who frequently utilize TLS datasets in their research, but do not have opportunities to be involved in field data acquisition.

地面沉降是西安市典型城市地质灾害之一,严重制约了西安城市地下空间的开发和利用,尤其是严重阻碍了城市轨道交通的发展.地层不均匀沉降变形增大,使地铁隧道衬砌结构产生纵向开裂破坏和隧道渗漏水等病害,这给西安地铁的建设及运营留下安全隐患.本文基于2007-2012年间120个地面沉降监测点的监测数据,根据等速率外推法预测了地铁沿线未来的地面沉降活动速率,运用单位变形量法计算出了地铁沿线地面沉降最大沉降量,其中胡家庙地面沉降中心最大沉降量为1 960 mm,小寨、大雁塔、沙坡及西工大等地面沉降中心为400～ 700 mm,而辛家庙、含元殿地面沉降中心为200～300mm.结合地铁工程自身的特点和重要性,对地铁沿线各区域地面沉降的危险性进行了评价,认为区域地面沉降对地铁线路的影响主要集中在地面沉降中心范围内,整体上线路南段危险性明显大于中段和北段.研究结果可为西安地铁工程规划设计、施工建设及安全运营提供重要依据.

Multi-temporal airborne laser scanning (ALS) surveys have become a prime consideration for detecting landslide movements and evaluating landslide risk in mountain areas. The minimum elevation change (or detectability) that can be detected by repeated ALS surveys has become a critical threshold for landslide researchers and engineers to decide if ALS is a capable tool for detecting targeted landslides and arranging the minimum time span between two scans if ALS is a choice. The National Center for Airborne Laser Mapping (NCALM) at the University of Houston conducted three repeated ALS surveys at the Slumgullion landslide site in Colorado, U.S. over one week in July of 2015. These repeated ALS surveys provide valuable datasets for evaluating the vertical detectability of multi-temporal ALS surveys in a typical mountain area. According to this study, the difference of digital elevation models (DDEM) derived from ALS has the ability of detecting a minimum elevation change of 5 cm over flatter and moderately rugged terrain areas (slope < 20 degrees) and a minimum of a 10-cm elevation change over rugged terrain areas (20 degrees < slope < 40 degrees). However, the DDEM values over highly rugged terrain areas (slope > 40 degrees), such as cliff and landslide scarps, should be interpolated with caution. Global Navigation Satellite Systems (GNSS) and Terrestrial Laser Scanning (TLS) surveys were also performed at the middle portion of the landslide area for assessing the accuracy of ALS datasets. The accuracy of ALS varies from approximately one decimeter (~10 cm) to one foot (~30 cm) depending on the roughness of terrain surface and vegetation coverage (point density). The detectability and accuracy estimates of ALS measurements obtained from the case study could be used as a reference for estimating the performance of modern ALS in mountain areas with similar topography and vegetation coverage.