钢纤维掺量对钢筋混凝土桥面板冲切性能影响

通过对钢纤维体积率为0和0.38%的双向板试件进行冲切试验,得到试件的破坏形态、钢筋和混凝土荷载-应变规律等,进而量化评估钢纤维掺量对钢筋混凝土桥面板冲切性能的影响。结果表明:钢纤维体积率为0与0.38%的试件相比,相同荷载作用下后者的钢筋、混凝土应变较小;首条裂缝的出现时间推迟;试件在冲切破坏时挠度变形较大且板底表面混凝土脱落较少。     

钢弹簧浮置板道床在西安地铁中减振效果分析

西安地铁二号线绕行通过西安钟楼,为降低地铁长期运营对钟楼的振动影响,在钟楼段采用钢弹簧浮置板道床进行减振。主要以地铁二号线运行影响下对钟楼的振动监测数据为基础,通过对钢弹簧浮置板道床段和普通道床段的振动实测值比较与分析,得出隧道内减振段和普通段的振动差异,以此评价钢弹簧浮置板道床在地铁应用中的减振效果。     

基于钢筋拉压力传递的预制空心板残余抗震性能研究

为提升建筑质量,分析在循环往复荷载作用下预制空心板整体抗震性能,研究基于钢筋拉、压应力传递的预制空心板残余抗震性能.制备不含钢筋预制空心板结构试件:不含钢筋试件、未使用钢筋拉压力传递间接搭接试件、使用钢筋拉、压应力传递灌孔构造边缘构建试件,对各试件循环施加地震荷载,记录各试件性能变化情况.试验结果表明,相比于压剪破坏的...     

Tectonic implications of the subduction of the Kyushu-Palau Ridge beneath the Kyushu,southwest Japan

The Kyushu-Palau Ridge(KPR), a remnant arc on the Philippine Sea Plate(PSP), is subducting beneath the Kyushu, southwest Japan. Influenced by the subducting KPR, the Kyushu subduction zone corresponding to the KPR is significantly different from Shikoku subduction zone in terms of gravity anomalies, seismicity, the stress state, and the subducting slab morphology. Significant negative free-air and Bouguer gravity anomalies are observed in a prolonged area of KPR, southeast of the Miyazaki Plain, indicating that this is where KPR overlaps the overriding plate. The gravity anomaly in this area is much lower than that in other areas where the inferred KPR extends, suggesting that the subduction of the buoyant KPR may cause the lower mantle density to decrease.More earthquakes have occurred in Hyuga-nada region where the KPR subducts than in Shikoku forearc and other areas in the Kyushu forearc, indicating that the subduction of the KPR enhances the local coupling between the subducting and overriding plates. The centroid moment tensor(CMT) mechanism of earthquakes shows that stress is concentrated in the accumulated crust beneath the Kyushu forearc corresponding to the KPR, and the shallow thrusting events in the obducting plate are caused by the KPR subduction. The buoyant KPR, with a large volume of low-density sediments, was responsible for the differences of the subduction depth and dip angle of the subducting Philippine Sea(PS) slab between northern Kyushu and Shikoku. The seismic gaps and the sudden change of the dipping angle of the subducting PS slab indicate that slab tear may have occurred along the west side of the KPR beneath southwest Kyushu. A two-tear model was proposed, and the subduction of the buoyant KPR was believed to play an important role in the slab tear.     

缅甸弧及邻区的壳幔S波速度结构与动力学过程

用适配滤波频时分析技术处理了锡龙（SHIO）、清迈（CHTO）、昆明（KMI）和拉萨LSA）台记录的长周期数字化面波记录,获取了穿过缅甸弧及周边地区的530条路径的Rayleigh波频散,这些频散的周期范围为10.45～105.03 s.在此基础上,以分格频散反演方法从混合路径频散中提取了1°×1°网格内的纯路径频散,并且由网格内的纯路径频散反演出深达200 km的S波速度结构,最后重建了缅甸弧及周边地区的S波速度三维结构.所得结果表明：大致以实皆断裂为分界,其东部地壳波速较低,其西部地壳波速较高.印度-缅甸地区岩石圈厚度为110～130 km,上地幔顶部S波速度为43～4.4 km/s;而缅甸弧东侧的滇缅泰地块下方为一低速地幔柱上涌区,其宽度为150～200 km左右,这里的岩石圈厚度为70～80 km,上地幔顶部S波速度为41～4.2 km/s.另外,S波速度结构还反映出这一构造格局呈南北向的空间展布,并且与该区地震震源分布、断裂走向、火山分布有很好的对应关系.     

板片深部俯冲动力学研究的新进展

高精度的层析成像结果显示了全球范围内形态各异的俯冲板片,这充分表明地球动力学过程的复杂性.本文简单回顾了影响板片俯冲的主要因素和对俯冲板片有关的,如对地震、火山、弧后变形等地球物理现象的各种合理解释.讨论中国东北新生代火山的地球动力学背景可能是不同于一般俯冲带火山的成因.     

刚性基础下复合地基褥垫层细观工作机制

垫层是保证变形协调、实现复合地基荷载合理分配的关键组件。但目前对垫层细观工作机制的认识还不够深入,参数选取主要依赖经验。为了进一步揭示垫层协调工作机制,利用自制试验装置进行了3种不同填料高度下的砂垫层可视化平面应变试验。结合2D DEM数值正交试验,揭示了不同尺寸参数组合下垫层的3种变形形态及其细观力链分布特征,指出变形形态与垫层相对厚度（厚度与桩间净距的比值）有关,并提出了按相对厚度控制垫层参数选取的建议。同时,通过垫层细观工作机制分析,提出垫层协调性能的评价指标,利用正交试验分析得到了垫层厚度与桩间净距是影响垫层变形协调能力的显著因素,给出了指标的取值上限值以指导垫层参数设计。     

Subduction geometry controls on dynamic topography: implications for the Jurassic Surat Basin

The Late Jurassic Springbok unconformity in the Surat Basin remains to date at odds with our understanding of basin-forming processes. A previously proposed cause for the unconformity is uplift related to the rifting of the Argo landmass from Western Australia, but the great distance between the Surat Basin and the Argo rift-zone argues against this interpretation. A more likely scenario is that the uplift was related to a west-dipping subduction zone along the east Australian margin. Numerous examples around the world link subduction processes, such as tears and detaching segments of the slab, to variations in surface topography. We used geodynamic forward modelling to generate uplift in the overriding plate of a subduction zone, as well as topographic changes that occur as subduction is disrupted by slab breakoff or tears. Our findings suggest that slab tearing can produce distribution and magnitude of uplift consistent with the Jurassic uplift in the Surat Basin, which potentially adds new insights into the tectonic evolution of eastern Australia.     

Late Paleocene–early Eocene granitoids in the Jiamusi Massif,NE China: Zircon U–Pb ages,geochemistry, and tectonic implications

Northeast (NE) China is characterized by large areas of Mesozoic and Paleozoic granitoids, whereas Cenozoic granitoids are scarce. This paper reports LA-ICP-MS zircon U–Pb ages and whole-rock geochemical data for late Paleocene–early Eocene granitoids from the Jiamusi Massif, NE China, in order to determine their petrogenesis and tectonic implications. Geochronological data indicate that the granodiorite and dioritic porphyry from the Wudingshan pluton formed at 51.5 ± 0.3 Ma and 56.3 ± 0.8 Ma, respectively. The biotite–quartz diorite, biotite granodiorite, and dioritic porphyry have high SiO₂ (68.38–70.06 wt.%), Al₂O₃ (15.34–15.79 wt.%), and Na₂O (3.96–4.49 wt.%) contents, low MgO contents (1.10–1.26 wt.%), A/CNK ratios of 0.99–1.11, and are classified as medium- to high-K calc-alkaline and weakly peraluminous I-type granitoids. They are enriched in LREEs and LILEs, and depleted in HFSEs, with Nb/Ta ratios of 10.4–15.0. Moreover, they have negative Nb–Ta–Ti anomalies, indicating that they were derived from continental crust. Combining with the previously published isotopic data and regional geological results, we suggest that the late Paleocene–early Eocene granitoids (56–52 Ma) were probably derived from partial melting of juvenile lower crust, and formed in an active continental margin setting, possibly related to subduction slab rollback of the Paleo-Pacific Plate.