Experimental study and numerical analysis on bearing behaviors of super-long rock-socketed bored pile groups

A centrifuge modeling test and a three-dimensional finite element analysis（FEA）of super-long rock-socketed bored pile groups of the Tianxingzhou Bridge are proposed.Based on the similarity theory,different prototypical materials are simulated using different indicators in the centrifuge model.The silver sand,the shaft and the pile cap are simulated according to the natural density,the compressive stiffness and the bending stiffness,respectively.The finite element method（FEM）is implemented and analyzed in ANSYS,in which the stress field during the undisturbed soil stage,the boring stage,the concrete-casting stage and the curing stage are discussed in detail.Comparisons in terms of load-settlement,shaft axial force distribution and lateral friction between the numerical results and the test data are carried out to investigate the bearing behaviors of super-long rock-socketed bored pile groups under loading and unloading conditions.Results show that there is a good agreement between the centrifuge modeling tests and the FEM.In addition,the load distribution at the pile top is complicated,which is related to the stiffness of the cap,the corresponding assumptions and the analysis method.The shaft axial force first increases slightly with depth then decreases sharply,and the rate of decrease in rock is greater than that in sand and soil.

Reversible Oxygen-Rich Functional Groups Grafted 3D Honeycomb-Like Carbon Anode for Super-Long Potassium Ion Batteries

Studies have found that oxygen-rich-containing functional groups in carbon-based materials can be used as active sites for the storage performance of K^(+),but the basic storage mechanism is still unclear.Herein,we construct and optimize 3D honeycomb-like carbon grafted with plentiful COOH/C=O functional groups(OFGC)as anodes for potassium ion batteries.The OFGC electrode with steady structure and rich functional groups can effectively contribute to the capacity enhancement and the formation of stable solid electrolyte interphase(SEI)film,achieving a high reversible capacity of 230 mAh g^(-1) at 3000 mA g^(-1) after 10,000 cycles(almost no capacity decay)and an ultra-long cycle time over 18 months at 100 mA g^(-1).The study results revealed the reversible storage mechanism between K^(+)and COOH/C=O functional groups by forming C-O-K compounds.Meanwhile,the in situ electrochemical impedance spectroscopy proved the highly reversible and rapid de/intercalation kinetics of K+in the OFGC electrode,and the growth process of SEI films.In particular,the full cells assembled by Prussian blue cathode exhibit a high energy density of 113 Wh kg^(-1) after 800 cycles(calculated by the total mass of anode and cathode),and get the light-emitting diodes lamp and ear thermometer running.

Realizing super-long Cu_2O nanowires arrays for high-efficient water splitting applications with a convenient approach

Nanowire(NW) structures is an alternative candidate for constructing the next generation photoelectrochemical water splitting system, due to the outstanding optical and electrical properties. NW photoelectrodes comparing to traditional semiconductor photoelectrodes shows the comparatively shorter transfer distance of photo-induced carriers and the increase amount of the surface reaction sites, which is beneficial for lowering the recombination probability of charge carriers and improving their photoelectrochemical(PEC) performances. Here, we demonstrate for the first time that super-long Cu_2O NWs, more than 4.5 μm,with highly efficient water splitting performance, were synthesized using a cost-effective anodic alumina oxide(AAO) template method. In comparison with the photocathode with planar Cu_2O films, the photocathode with Cu_2O NWs demonstrates a significant enhancement in photocurrent, from –1.00 to –2.75 mA/cm^2 at –0.8 V versus Ag/AgCl. After optimization of the photoelectrochemical electrode through depositing Pt NPs with atomic layer deposition(ALD) technology on the Cu_2O NWs, the plateau of photocurrent has been enlarged to –7 mA/cm^2 with the external quantum yield up to 34% at 410 nm. This study suggests that the photoelectrode based on Cu_2O NWs is a hopeful system for establishing high-efficiency water splitting system under visible light.

Axial bearing behavior of super-long piles in deep soft clay over stiff layers

In order to find out the bearing behavior of super-long piles located in deep soft clay over stiff layers around Dongting Lake, China, a test pile was first designed with the field loading test finished afterward. Based on the measured test results, load transfer mechanism and bearing behavior of the pile shaft were discussed in detail. Then, by introducing a bi-linear model for shaft friction and the tri-linear model for pile tip resistance, respectively, the governing differential equation of pile soil system was set up by the load transfer method with the analytical solutions derived as well, taking into account the effect by stratified feature and various bearing conditions of subsoil, material nonlinearity, and the sediment under pile tip. Furthermore, formulas to determine the axial capacity of super-long piles by the pile top settlement were advised and applied to analyze the test pile. Good agreement between the predicted load settlement variations and the measured data is obtained to verify the validity of the present method. The results also show that, the axial bearing capacity of super-long piles should be controlled by the allowable pile top settlement, and buckling stability of the pile shaft should be paid attention as well.

Buckling analysis of super-long rock-socketed filling piles in soft soil area by element free Galerkin method

In order to discuss the buckling stability of super-long rock-socketed filling piles widely used in bridge engineering in soft soil area such as Dongting Lake, the second stability type was adopted instead of traditional first type, and a newly invented numerical analysis method, i.e. the element-free Galerkin method (EFGM), was introduced to consider the non-concordant deformation and nonlinearity of the pile-soil interface. Then, based on the nonlinear elastic-ideal plastic pile-soil interface model, a nonlinear iterative algorithm was given to analyze the pile-soil interaction, and a program for buckling analysis of piles by the EFGM (PBAP-EFGM) and arc length method was worked out as well. The application results in an engineering example show that, the shape of pile top load-settlement curve obtained by the program agrees well with the measured one, of which the difference may be caused mainly by those uncertain factors such as possible initial defects of pile shaft and the eccentric loading during the test process. However, the calculated critical load is very close with the measured ultimate load of the test pile, and the corresponding relative error is only 5.6%, far better than the calculated values by linear and nonlinear incremental buckling analysis (with a greater relative error of 37.0% and 15.4% respectively), which also verifies the rationality and feasibility of the present method.

Challenges and Thoughts on Risk Management and Control for the Group Construction of a Super-Long Tunnel by TBM

The total length of the second stage of the water supply project in the northern areas of the Xinjiang Uygur Autonomous Region is 540 km, of which the total length of the tunnels is 516 km. The total tun- neling mileage is 569 km, which includes 49 slow-inclined shafts and vertical shafts. Among the tunnels constructed in the project, the Ka-Shuang tunnel, which is a single tunnel with a length of 283 kin, is cur- rently the longest water-conveyance tunnel in the world. The main tunnel of the Ka-Shuang tunnel is divided into 18 tunnel-boring machine （TBM） sections, and 34 drilling-and-blasting sections, with 91 tunnel faces. The construction of the Ka-Shuang tunnel has been regarded as an unprecedented challenge for project construction management, risk control, and safe and efficient construction; it has also pre- sented higher requirements for the design, manufacture, operation, and maintenance of the TBMs and their supporting equipment. Based on the engineering characteristics and adverse geological conditions, it is necessary to analyze the major problems confronted by the construction and systematically locate disaster sources. In addition, the risk level should be reasonably ranked, responsibility should be clearly identified, and a hierarchical-control mechanism should be established. Several techniques are put for- ward in this paper to achieve the objectives mentioned above; these include advanced geological prospecting techniques, intelligent tunneling techniques combined with the sensing and fusion of infor- mation about rock parameters and mechanical parameters, monitoring and early-warning techniques, and modern information technologies. The application of these techniques offers scientific guidance for risk control and puts forward technical ideas about improving the efficiency of safe tunneling. These techniques and ideas have great significance for the development of modern tunneling technolo- gies and research into major construction equipment.

Perturbation of symmetries for super-long elastic slender rods

This paper analyses perturbations of Noether symmetry, Lie symmetry, and form invariance for super-long elastic slender rod systems. Criterion and structure equations of the symmetries after disturbance are proposed. Considering perturbation of all infinitesimal generators, three types of adiabatic invariants induced by perturbation of symmetries for the system are obtained.

Structure properties and Noether symmetries for super-long elastic slender rod

DNA is a nucleic acid molecule with double-helical structures that are special symmetrical structures attracting great attention of numerous researchers. The super-long elastic slender rod, an important structural model of DNA and other long-train molecules, is a useful tool in analysing the symmetrical properties and the stabilities of DNA. This paper studies the structural properties of a super-long elastic slender rod as a structural model of DNA by using Kirchhoff＇s analogue technique and presents the Noether symmetries of the model by using the method of infinitesimal transformation. Baaed on Kirchhoff＇s analogue it analyses the generalized Hamilton canonical equations. The infinitesimal transfornaationa with rcspect to the radial coordinnte, the gonarnlizod coordinates, and the Cluasi-momenta of 5he model are introduced. The Noether gymmetries and conserved qugntities of the model are obtained.

Electrochemical Introduction of Active Sites into Super-long Carbon Nanotubes for Enhanced Capacitance

Electrochemical cyclic voltammetric（CV） scan was applied to inducing the partial oxidation and defects of carbon nanotubes（CNTs）.The electrochemically induced functional groups and physical defects were demonstrated to show positive effects on the nanotube capacitance,as exemplified by super-long CNT arrays as model for the easy fabrication of CNT electrodes.Specifically,the initial hydrophobic nanotube surface becomes hydrophilic and a ten-time enhancement in capacitance is observed with respect to the pristine CNT sample.Thus,the electrochemical CV pretreatment can be used as an effective approach to activate the CNT surface for an enhanced electrochemical performance in capacitors,and many other advanced devices beyond capacitors,such as electrochemical sensors and batteries.

Seismic performance evaluation for super-long span cable-stayed bridges

Based on the capacity/demand(C/D)analysis of bridge components,and life cycle and performance based seismic design principles,a practical approach is developed for the seismic performance evaluation of super-long span cable-stayed bridges.According to the approach,the seismic performance evaluation of the Sutong Bridge,which is a cable-stayed bridge with a main span of 1 088 m,is completed,and the practicality of the approach is validated.The earthquake resistance level for super-long span cable-stayed bridges is discussed,including the earthquake level,its corresponding structural performance and check indices.And a set of formula for capacity/demand ratio calculation of bridge components is proposed.

Migration law of respirable dust on a super-long fully mechanized double-shearer working face

In order to understand the migration law of respirable dust and gain reasonable design parameters for dust control on a super-long double-shearer fully mechanized working face, this paper describes research carried out using a numerical simulation package(Fluent) based on gas-solid coupling dispersed multiphase flow model and field measurement to research different technology modes, dust distribution law at different intervals where shearers work in opposite directions on the lower 9303 face, No. 2 Jining Mine,Yankuang Coal Mining Co. Results show that the concentration of dust 3–6 m away from the shearers working in the same directions was large, while the impact area of respirable dust near the shearer increased significantly to 5–6 m with the distance between two shearers working in opposite directions.The concentration of dust on a double-shearer face was considerably higher than that of a face with one shear under the combined effect of wind speed on the face and disturbed wind around the shearer, while the dust concentration near the shearer on the return side was considerably higher than that on the inlet side. The concentration of dust on a double-shearer face along the airflow declined slowly so that dust was hard to control. Simulation results confirmed the results of field measurement, which could provide reference for dust prevention design.

Predictive analysis of stress regime and possible squeezing deformation for super-long water conveyance tunnels in Pakistan

The prediction of the stress field of deep-buried tunnels is a fundamental problem for scientists and engineers. In this study, the authors put forward a systematic solution for this problem. Databases from the World Stress Map and the Crustal Stress of China, and previous research findings can offer prediction of stress orientations in an engineering area. At the same time, the Andersonian theory can be used to analyze the possible stress orientation of a region. With limited in-situ stress measurements, the Hock-Brown Criterion can be used to estimate the strength of rock mass in an area of interest by utilizing the geotechnical investigation data, and the modified Sheorey＇s model can subsequently be employed to predict the areas＇ stress profile, without stress data, by taking the existing in-situ stress measurements as input parameters. In this paper, a case study was used to demonstrate the application of this systematic solution. The planned Kohala hydropower plant is located on the western edge of Qinghai-Tibet Plateau. Three hydro-fracturing stress measurement campaigns indicated that the stress state of the area is SH - Sh 〉 Sv or SH 〉Sv 〉 Sh. The measured orientation of Sn is NEE （N70.3°-89°E）, and the regional orientation of SH from WSM is NE, which implies that the stress orientation of shallow crust may be affected by landforms. The modified Sheorey model was utilized to predict the stress profile along the water sewage tunnel for the plant. Prediction results show that the maximum and minimum horizontal principal stres- ses of the points with the greatest burial depth were up to 56.70 and 40.14 MPa, respectively, and the stresses of areas with a burial depth of greater than 500 m were higher. Based on the predicted stress data, large deformations of the rock mass surrounding water conveyance tunnels were analyzed. Results showed that the large deformations will occur when the burial depth exceeds 300 m. When the burial depth is beyond 800 m, serious squeezing deformations will occur in the surrounding rock masses, thus requiring more attention in the design and construction. Based on the application efficiency in this case study, this prediction method proposed in this paper functions accurately.

Key Technologies for Design of Changqing Yellow River Super-long Bridge of Zhengzhou Ji'nan HSR

Changqing Yellow River Super-long Bridge of Zhengzhou-Ji'nan HSR is a partial cable-stayed bridge with concrete main girder and a unit length of 1,080 m.Studies are carried out on the key technologies of bridge design,and the main conclusions are as follows:The whole unit adopts the supporting system of tower pier consolidation and tower-beam separation,and each pier is provided with seismic mitigation and isolation bearing;shaped-steel reinforced concrete bridge tower is adopted to bring into full play the tensile performance of steel and the compressive performance of concrete,and avoid the construction challenges of setting up multi-layer and multi-stirrup reinforcement while improving the bearing capacity of section;a new type of double-side and bi-directional anti-skid anchorage device is adopted for the cable saddle of wire divider pipe in order to withstand the unbalanced cable force,and verify the reliability of the anti-skid anchorage device by solid model test;and large-segment cantilever pouring design is adopted for the main girder with a maximum segment length of 8 m to effectively shorten the construction period of the bridge.

Parameter effects on the dynamic characteristics of a super-long-span triple-tower suspension bridge

A 3D finite element model for the Taizhou Yangtze River Bridge,the first triple-tower long-span suspension bridge in China,is established based on the nonlinear finite element software ABAQUS,and the dynamic characteristics of the bridge are analyzed using the LANCZOS eigenvalue solution method. The study focuses on the effects of the vertical,lateral and torsional stiffness of the steel box girder,the rigid central buckle and the elastic restraints connecting the towers and the steel box girder on the dynamic characteristics of the triple-tower suspension bridge. Our results show that,in general,the dynamic characteristics of the triple-tower suspension bridge are similar to those of two-tower suspension bridges. The vertical,lateral and torsional stiffness of the steel box girder have different effects on the dynamic characteristics of triple-tower suspension bridges. The elastic re-straints have a more significant effect on the dynamic characteristics than the central buckle,and decreasing the stiffness of the elastic restraints results in the appearance of a longitudinal floating vibration mode of the bridge. Also,rigid central buckles have a greater influence on the dynamic characteristics of triple-tower suspension bridges than on those of two-tower suspension bridges. The results obtained could serve as a valuable numerical reference for analyzing and designing super-long-span triple-tower suspension bridges.

Modified super-long down-regulation protocol improves fertilization and pregnancy in patients with poor ovarian responses

Background The successful end-point of in vitro fertilization （IVF） treatment is for a woman to give live birth. This outcome is based on various factors including adequate number of retrieved eggs. Failure to recruit adequate follicles, from which the eggs are retrieved, is called a ＂poor response＂. How to improve the clinical pregnancy rates of poor responders was one of the tough problems for IVF. Methods The study involved 51 patients who responded poorly to high dose gonadotropin treatment in their previous cycles at our reproductive center, between April 2010 and February 2012. The previous cycle （group A） received routine long protocol; the subsequent cycle （group B） received modified super-long down-regulation protocol. The primary outcome of the study was the number of oocytes fertilized. The increase in the pregnancy rate was the secondary outcome. Differences between the groups were assessed by using Student＇s t test and Z2 test where appropriate. Results The patients＇ average age was （36.64±3.85） years. The mean duration of ovarian stimulation cycles of the group A patients was longer than those of the group B patients. The total dose of follicle-stimulating hormone （FSH） was significantly lower in the subsequent cycle. The peak value of serum estradiol on human chorionic gonadotrophin （hCG） day was lower in group A as compared with group B. The number of metaphase II oocytes recovered was significantly higher in group B. The cleavage rate in group A was significantly lower than in group B, 49 patients in group B reached embryo transfer stage, while 46 patients in group A reached this stage. Patients in group B received significantly more embryos per transfer as compared with group A. More pregnancies and more clinical pregnancies with fetal heart activity were achieved in group B. Conclusions This comparative trial shows that poor responder women undergoing repeated assisted reproduction treatment using modified super-long down-regulation protocol achieve more oocytes, leading to higher fertilization rate, compared to women receiving routine long protocol. Our study also showed that clinical pregnancy rate was significantly improved.

Revised Super-long Down-regulation Protocol Improves the Outcome of Infertile Patients with Repeated Implantation Failure in IVF/ICSI-ET

Objective To investigate the outcome of revised super-long down-regulation protocol （RSDP） for in vitro fertilization / intracytoplasmic sperm injection-embryo transfer （1VF/1CS1-ET） in the special infertile patients with repeated implantation failure （RIF）. Methods Patients with RIF were divided into RSDP group and routine long downregulation protocol （RLDP） group. In RSDP group, gonadotropin releasing hormone agonist （GnRHa） was injected intramuscularly by 2.5 mg in mid-luteal phase for the ftrst time and 1.25 mg after 28 d; gonadotropin （Gn） was started 14 d later after the second GnRHa dose. IVF/ICSI-ET was performed according to the routine procedure. The clinical outcomes of RSDP group were compared with those of RLDP group. Results In RSDP group, the number of retrieved oocytes and valid embryos was significantly lower （P〈0.05）; there were no significant differences about fertilization rate （P〉0. 05）; both good-quality embryo rate and implantation rate were significantly increased （P〈0. 005）; clinical pregnancy rate was obviously improved （P〈0. 05）, as compared with RLDP group.Conclusion RSDP can improve the IVF outcomes significantly in RIF patients.

截至2023年底中国10km以上特长公路隧道统计与分析

在隧道行业相关单位的大力支持及既有统计数据的基础上,对截至2023年底中国已建成运营、正在建设、规划设计的共计74座长度10 km以上的特长公路隧道进行统计,其中,已建成运营特长公路隧道25座,正在建设特长公路隧道31座,规划设计特长公路隧道18座。从隧道长度、所在省份、公路等级、地理位置、技术标准、施工工法、设计与施工单位等方面,对中国已建成运营、正在建设、规划设计的长度10 km以上的特长公路隧道建设情况进行分析,其中:长度在10~14.9 km的隧道共62座,长度在15~19.9 km的隧道共10座,长度大于20 km的隧道共2座;隧道主要集中在中国西南部,约占63%,四川省最多,其次是云南省;高速公路隧道达65座,占比约为88%;山岭公路隧道68座,水下隧道6座;隧道技术标准以双向4车道为主;隧道施工工法以钻爆法为主,近些年出现了TBM+钻爆组合工法;隧道设计单位主要有31家;隧道施工单位主要有52家。

超长大跨度公铁合建桥梁结构体系研究

新建甬舟铁路西堠门公铁两用大桥连接金塘岛和册子岛,桥位处海域宽2.7 km,最大水深93 m,地形复杂,桥梁设计难度大。为研究超长大跨度公铁合建桥梁合理结构体系,结合地形地质条件,选取主跨1500 m悬索桥、斜拉桥及斜拉悬索协作体系3种桥型方案,对上部结构设计进行详细介绍,并从静力性能、动力性能、经济性能等方面对不同结构体系进行对比分析。研究表明:(1)与斜拉体系相比,协作体系桥可减小30%~50%的主梁内力和60%的桥塔内力,一定程度上解决了加劲梁承受巨大轴压力造成屈曲问题,并有效减小了桥塔规模;(2)与悬索桥相比,协作体系可减小50%的主缆内力,主缆钢丝和锚碇的工程量相应减小,施工难度得以降低,同时协作体系扭转频率更高,降低了结构在较低风速下发生涡激振动的可能性;(3)斜拉悬索协作体系能够充分发挥斜拉结构和悬索结构的组合优势,实现超大跨度的同时具有较大的纵向刚度和竖向刚度,满足铁路行车对结构刚度的要求;(4)对于主跨1500 m级超长大跨度公铁合建桥梁,斜拉悬索协作体系经济性更好。

秦岭天台山超长公路隧道群关键技术创新与实践

针对秦岭天台山超长公路隧道群在建设和运营过程中面临的工程建设难度大,运营管理复杂、安全风险高以及运营能耗高等诸多技术难题,围绕安全智慧运营、安全快速施工、单层衬砌支护、自然能源利用等方向,系统总结了秦岭山区特殊地质地形条件下32 km隧道群建设与运营过程中系列创新技术成果。主要结论:1)通过超长隧道群安全智慧运营技术创新与应用,破解山区超长连续公路隧道群运营安全保障难题;2)通过公路隧道安全快速施工技术创新与应用,突破超长大断面公路隧道机械化安全快速施工瓶颈;3)通过公路隧道单层衬砌支护技术创新与应用,构建硬质岩公路隧道单层衬砌支护体系;4)通过公路隧道利用自然能源技术推广应用,探索超长公路隧道绿色低碳运行。