Thermal performance of cast-in-place piles with artificial ground freezing in permafrost regions

During the construction of cast-in-place piles in warm permafrost,the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding permafrost.Since the bearing capacity of the pile is quite small before the full freeze-back,the quick refreezing of the native soils surrounding the cast-in-place pile has become the focus of the infrastructure construction in permafrost.To solve this problem,this paper innovatively puts forward the application of the artificial ground freezing(AGF)method at the end of the curing period of cast-in-place piles in permafrost.A field test on the AGF was conducted at the Beiluhe Observation and Research Station of Frozen Soil Engineering and Environment(34°51.2'N,92°56.4'E)in the Qinghai Tibet Plateau(QTP),and then a 3-D numerical model was established to investigate the thermal performance of piles using AGF under different engineering conditions.Additionally,the long-term thermal performance of piles after the completion of AGF under different conditions was estimated.Field experiment results demonstrate that AGF is an effective method to reduce the refreezing time of the soil surrounding the piles constructed in permafrost terrain,with the ability to reduce the pile-soil interface temperatures to below the natural ground temperature within 3 days.Numerical results further prove that AGF still has a good cooling effect even under unfavorable engineering conditions such as high pouring temperature,large pile diameter,and large pile length.Consequently,the application of this method is meaningful to save the subsequent latency time and solve the problem of thermal disturbance in pile construction in permafrost.The research results are highly relevant for the spread of AGF technology and the rapid building of pile foundations in permafrost.

Linear monitoring for cast-in-place reinforced concrete arch bridge construction

Linear monitoring is an important link of bridge construction control,which is conducted in key processes of construction to ensure the security of bridge in construction procedure. Combining with main arch construction monitoring program of No. 2 bridge in north district of Changbai international tourism resort,main content and key technologies are recommended. Considering the various influential factors during the construction process,linear adjustment is handled to ensure that the stress and linear of main arch meet design requirements.

ESMO2023:恩扎卢胺联合雄激素剥夺治疗对比安慰剂联合雄激素剥夺治疗在中国转移性激素敏感性前列腺癌患者中的疗效和安全性(中国ARCHES)

2019年发表的全球ARCHES试验(NCT02677896)结果显示,与安慰剂(placebo,PBO)+雄激素剥夺治疗(androgen deprivation therapy,ADT)相比,恩扎卢胺+ADT延长了转移性激素敏感性前列腺癌(metastatic hormone-sensitive prostate cancer,mHSPC)患者的总生存期和放射影像学无进展生存期(radiographic progression-free survival,rPFS)^([1])。然而,该试验无中国患者入组。欧洲肿瘤内科学会(European Society for Medical Oncology,ESMO)2023年会议报道了中国ARCHES研究(NCT04076059)的初步结果,这是一项评估恩扎卢胺+ADTvs.PBO+ADT在中国m HSPC患者中的疗效和安全性的多中心、随机、双盲、PBO对照的Ⅲ期试验^([2])。

Refreezing of cast-in-place piles under various engineering conditions

In the construction of the Qinghai-Tibet Power Transmission Line （QTPTL）, cast-in-place piles （CIPPs） are widely applied in areas with unfavorable geological conditions. The thermal regime around piles in permafrost regions greatly affects the stability of the towers as well as the operation of the QTPTL. The casting of piles will markedly affect the thermal regime of the surrounding permafrost because of the casting temperature and the hydration heat of cement. Based on the typical geological and engineering conditions along the QTPTL, thermal disturbance ofa CIPP to surrounding permafrost under different casting seasons, pile depths, and casting temperatures were simulated. The results show that the casting season （summer versus winter） can influence the refreezing process of CIPPs, within the first 6 m of pile depth. Sixty days after being cast, CIPPs greater than 6 m in depth can be frozen regardless of which season they were cast, and the foundation could be reffozen after a cold season. Comparing the refreezing characteristics of CIPPs cast in different seasons also showed that, without considering the ground surface conditions, warm seasons are more suitable for casting piles. With the increase of pile depth, the thermal effect of a CIPP on the surrounding soil mainly expands vertically, while the lateral heat disturbance changes little. Deeper, longer CIPPs have better stability. The casting temperature clearly affects the thermal disturbance, and the radius of the melting circle increases with rising casting temperature. The optimal casting temperature is between 2 ℃ and 9 ℃.

Seismic performance analysis and design suggestion for frame buildings with cast-in-place staircases

Many staircases in reinforced concrete （RC） frame structures suffered severe damage during the Wenchuan earthquake. Elastic analyses for 18 RC structure models with and without staircases are conducted and compared to study the influence of the staircase on the stiffness, displacements and internal forces of the structures. To capture the yielding development and damage mechanism of frame structures, elasto-plastic analysis is carried out for one of the 18 models. Based on the features observed in the analyses, a new type of staircase design i.e., isolating them from the master structure to eliminate the effect of K-type struts, is proposed and discussed. It is concluded that the proposed method of staircase isolation is effective and feasible for engineering design, and does not significantly increase the construction cost.

Physical modeling of behaviors of cast-in-place concrete piled raft compared to free-standing pile group in sand

Similar to free-standing pile groups, piled raft foundations are conventionally designed in which the piles carry the total load of structure and the raft bearing capacity is not taken into account. Numerous studies indicated that this method is too conservative. Only when the pile cap is elevated from the ground level,the raft bearing contribution can be neglected. In a piled raft foundation, pileesoileraft interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors of piled raft foundations, very few experimental studies are reported in the literature. The available laboratory studies mainly focused on steel piles. The present study aims to compare the behaviors of piled raft foundations with free-standing pile groups in sand, using laboratory physical models. Cast-in-place concrete piles and concrete raft are used for the tests. The tests are conducted on single pile, single pile in pile group, unpiled raft, free-standing pile group and piled raft foundation. We examine the effects of the number of piles, the pile installation method and the interaction between different components of foundation. The results indicate that the ultimate bearing capacity of the piled raft foundation is considerably higher than that of the free-standing pile group with the same number of piles. With installation of the single pile in the group, the pile bearing capacity and stiffness increase. Installation of the piles beneath the raft decreases the bearing capacity of the raft. When the raft bearing capacity is not included in the design process, the allowable bearing capacity of the piled raft is underestimated by more than 200%. This deviation intensifies with increasing spacing of the piles.

Field observation of the thermal disturbance and freezeback processes of cast-in-place pile foundations in warm permafrost regions

The bearing capacity of pile foundations is affected by the temperature of the frozen soil around pile foundations.The construction process and the hydration heat of cast-in-place(CIP)pile foundations affect the thermal stability of permafrost.In this paper,temperature data from inside multiple CIP piles,borehole observations of ground thermal status adjacent to the foundations and local weather stations were monitored in warm permafrost regions to study the thermal influence process of CIP pile foundations.The following conclusions are drawn from the field observation data.(1)The early temperature change process of different CIP piles is different,and the differences gradually diminish over time.(2)The initial concrete temperature is linearly related with the air temperature,net radiation and wind speed within 1 h before the completion of concrete pouring;the contributions of the air temperature,net radiation,and wind speed to the initial concrete temperature are 51.9%,20.3%and 27.9%,respectively.(3)The outer boundary of the thermal disturbance annulus is approximately 2 m away from the pile center.It took more than 224 days for the soil around the CIP piles to return to the natural permafrost temperature at the study site.

Field study of plastic tube cast-in-place concrete pile

The compositions, technical principles and construction equipments of a new piling method used for ground improvement plastic tube cast-in-place concrete pile were introduced. The results from static load tests on single piles with different forms of pile shoes and on their composite foundations were analyzed. The distribution patterns of axial force, shaft friction and toe resistance were studied based on the measurements taken from buried strain gauges. From the point of engineering application, the pile has merits in convenient quality control, high bearing capacity and reliable quality, showing higher reasonability, advancement and suitability than other ground improvement methods. The pile can be adopted properly to take place of ordinary ground improvement method, achieving greater economical and social benefits.

Health diagnosis of ultrahigh arch dam performance using heterogeneous spatial panel vector model

Currently,more than ten ultrahigh arch dams have been constructed or are being constructed in China.Safety control is essential to long-term operation of these dams.This study employed the flexibility coefficient and plastic complementary energy norm to assess the structural safety of arch dams.A comprehensive analysis was conducted,focusing on differences among conventional methods in characterizing the structural behavior of the Xiaowan arch dam in China.Subsequently,the spatiotemporal characteristics of the measured performance of the Xiaowan dam were explored,including periodicity,convergence,and time-effect characteristics.These findings revealed the governing mechanism of main factors.Furthermore,a heterogeneous spatial panel vector model was developed,considering both common factors and specific factors affecting the safety and performance of arch dams.This model aims to comprehensively illustrate spatial heterogeneity between the entire structure and local regions,introducing a specific effect quantity to characterize local deformation differences.Ultimately,the proposed model was applied to the Xiaowan arch dam,accurately quantifying the spatiotemporal heterogeneity of dam performance.Additionally,the spatiotemporal distri-bution characteristics of environmental load effects on different parts of the dam were reasonably interpreted.Validation of the model prediction enhances its credibility,leading to the formulation of health diagnosis criteria for future long-term operation of the Xiaowan dam.The findings not only enhance the predictive ability and timely control of ultrahigh arch dams'performance but also provide a crucial basis for assessing the effectiveness of engineering treatment measures.

Design and construction of high and large span cast-in-place reinforced concrete cantilever flowering frame beam

The high and large span cast-in-place reinforced concrete cantilever structure of the office building of some court, which is located I-steel at the cantilever and used steel pipe scaffold as the support, has guaranteed the frame body and structure security by the frame body calculating, on-site test and reasonable construction order.

Recent Construction Technology Innovations and Practices for Large-Span Arch Bridges in China

Arch bridges provide significant technical and economic benefits under suitable conditions.In particular,concrete-filled steel tubular(CFST)arch bridges and steel-reinforced concrete(SRC)arch bridges are two types of arch bridges that have gained great economic competitiveness and span growth potential due to advancements in construction technology,engineering materials,and construction equipment over the past 30 years.Under the leadership of the author,two record-breaking arch bridges—that is,the Pingnan Third Bridge(a CFST arch bridge),with a span of 560 m,and the Tian’e Longtan Bridge(an SRC arch bridge),with a span of 600 m—have been built in the past five years,embodying great technological breakthroughs in the construction of these two types of arch bridges.This paper takes these two arch bridges as examples to systematically summarize the latest technological innovations and practices in the construction of CFST arch bridges and SRC arch bridges in China.The technological innovations of CFST arch bridges include cable-stayed fastening-hanging cantilevered assembly methods,new in-tube concrete materials,in-tube concrete pouring techniques,a novel thrust abutment foundation for nonrocky terrain,and measures to reduce the quantity of temporary facilities.The technological innovations of SRC arch bridges involve arch skeleton stiffness selection,the development of encasing concrete materials,encasing concrete pouring,arch rib stress mitigation,and longitudinal reinforcement optimization.To conclude,future research focuses and development directions for these two types of arch bridges are proposed.

Numerical Simulation Analysis of Welded Joints in Arch Ribs of Large Span Steel Pipe Arch Bridges

In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for welded joints of arch-ribbed steel tubes using 7-,8-and 9-layer welds is carried out and its accuracy is demonstrated.The steel pipe welding temperature changes,residual stress distribution,different processes residual stress changes in the law,the prediction of post-weld residual stress distribution and deformation are studied in this paper.The results show that the temperature field values and test results are more consistent with the accuracy of numerical simulation of welding,the welding process is mainly in the form of heat transfer;Residual high stresses are predominantly distributed in the Fusion zone(FZ)and Heat-affected zone(HAZ),with residual stress levels tending to decrease from the center of the weld along the axial path,the maximum stress appears in the FZ and HAZ junction;The number of welding layers has an effect on the residual stress distribution,the number of welding layers increases,the residual stress tends to decrease,while the FZ and HAZ high stress area range shrinks;Increasing the number of plies will increase the amount of residual distortion.

中国汽油价格波动基于ARCH模型的分析研究

本文采用ARCH模型,并使用Eviews10统计学软件,利用2014年到2024年近11年的92号汽油价格,分析中国汽油市场价格的波动性。通过分析北京、上海、广州三个地区的92号汽油价格,表明中国汽油价格残差序列具有明显的“尖峰厚尾”特征,也具有显著的波动性特性。同时也印证了ARCH模型能够很好地描述中国汽油价格市场的波动性特性。本文最后根据实证分析结果,对中国应积极应对国际油价的变化,提出可操作性建议。

Influence of axial stress on failure characteristics of deep arched hard rock roadway

To study the influence of axial stress on the failure characteristics of deep arched roadway considering structural effect,true triaxial compression tests were conducted on cubic granite specimens with a three-centered arched hole structure.A video monitoring device was utilized to record the failure process of surrounding rocks.The test results show that under 10−60 MPa axial stress,the surrounding rock failure process included the calm stage,particle ejection stage,fragment ejection stage,and rock slice buckling and spalling stage.Under higher axial stresses(70 and 80 MPa),the failure process is characterized by violent fragment spray during the fourth stage.As the axial stress increases,the failure of surrounding rock increases,while the initial vertical failure stress first increases and then decreases.According to the failure characteristics of roadway under different axial stresses,arranging the roadway along the direction of a moderate axial stress level is desired.

A Nonlinear Explicit Model of A Non-Circular Subsea Tunnel-Liner System with An FGM Inverted Arch Under Mechanical Loading and Fire Fields

This paper proposes an explicit scheme to analyze the failure of a subsea polyhedral tunnel-liner system with an inverted arch under mechanical loading and fire fields.The thin-walled liner is made of Functionally Graded Materials(FGMs),which may improve the stability behavior of the tunnel-liner system.Hydrostatic pressure is inevitable in the liner since underground water may penetrate the cracks of the tunnel,and reach the outer surface of the liner.In addition,an elevated temperature loading is taken into account,considering that fire may occur in the tunnel-liner system.Under the combination of mechanical loading and thermal loading,the liner deforms into a single-lobe shape,which is depicted by a trigonometric function.The total potential energy is expressed quantitatively after the energy approach and thin-walled shell theory are used.The minimum potential energy is obtained when the critical buckling occurs.The critical buckling pressure is calculated,which considers the effect of the thermal field.The present analytical prediction is subsequently compared precisely with other closed-form solutions.Finally,the effects of several parameters,such as the geometric shapes,temperature variations,and volume fraction indices,are discussed to further survey the buckling performance of the nonlinear buckling of an FGM polyhedral liner with an inverted arch.One may address a polyhedral liner with fewer polyhedral sides,and a lower volume fraction index is recommended to rehabilitate cracked tunnels in engineering applications.

Prediction model of surrounding rock deformation in doublecontinuous-arch tunnel based on the ABC-WNN

Purpose–The wavelet neural network(WNN)has the drawbacks of slow convergence speed and easy falling into local optima in data prediction.Although the artificial bee colony(ABC)algorithm has strong global optimization ability and fast convergence speed,it also has the drawbacks of slow speed while finding the optimal solution and weak optimization ability in the later stage.Design/methodology/approach–This article uses an ABC algorithm to optimize the WNN and establishes an ABC-WNN analysis model.Based on the example of the Jinan Yuhan underground tunnel project,the deformation of the surrounding rock of the double-arch tunnel crossing the fault fracture zone is predicted and analyzed,and the analysis results are compared with the actual detection amount.Findings–The comparison results show that the predicted values of the ABC-WNN model have a high degree of fitting with the actual engineering data,with a maximum relative error of only 4.73%.On this basis,the results show that the statistical features of ABC-WNN are the lowest,with the errors at 0.566 and 0.573,compared with the single back propagation(BP)neural network model and WNN model.Therefore,it can be derived that the ABC-WNN model has higher prediction accuracy,better computational stability and faster convergence speed for deformation.Originality/value–This article uses firstly the ABC-WNN for the deformation analysis of double-arch tunnels.This attempt laid the foundation for artificial intelligence prediction in deformation analysis of multiarch tunnels and small clearance tunnels.It can provide a new and effective way for deformation prediction in similar projects.

Effects of comprehensive nursing with cognitive behavioral therapy in orthodontic osteodilated arch treatment

BACKGROUND This work explored the effects of cognitive behavior therapy(CBT)-based comprehensive nursing intervention(CNI)mode in arch expansion to treat patients with orthodontic osteodilated arch(OOA).AIM To explore the application effect of CBT-based CNI model in orthodontic expansion arch treatment.METHODS Using convenient sampling method,81 patients with OOA were selected and rolled into a control group(Ctrl group,40 cases)and an observation group(Obs group,41 cases).During the treatment,patients in the Ctrl group received routine nursing intervention mode,and the those in the Obs group received CBT mode on the basis of this.Before and after intervention,the incidence of oral mucositis,the mastery rate of correct arch expansion method,self-rating anxiety scale score,soft scale index,and plaque index were compared for patients in different groups.In addition,satisfaction and complications were comparatively analyzed.RESULTS Incidence of oral mucositis in the Obs group was lower(14.6%vs 38.5%),and the mastery rate of correct arch expansion method was obviously higher(90.2%vs 55.0%)was obviously higher(all P<0.05).Meanwhile,the soft scale index and plaque index in the Obs group were much lower(P<0.05).The compliance(90.24%)and satisfaction(95.12%)in the Obs group were greatly higher(P<0.05).CONCLUSION The CBT-based CNI mode greatly improved the mastery rate of correct arch expansion method during arch expansion in treating patients with OOA and enhanced the therapeutic effect of arch expansion and the oral health of patients,improving the patient compliance.

基于SARIMA-ARCH的电量预测模型

电量预测是供电单位购电的重要依据,是电力经济稳定运行的根本基础。提出采用SARIMA-ARCH融合模型对某地区售电量进行预测。首先,采用季节时间序列分析方法(SARIMA)对月度电量时间序列进行建模,通过ACF和PACF图筛选确定出最佳模型阶数,得到季节性时间序列模型(SARIMA)基础预测模型;提取模型残差的波动性,建立自回归条件异方差(ARCH)模型;最后,将SARIMA-ARCH模型与常规SRIAM和ARIMA的预测值进行对比分析。结果表明,SARIMAARCH混合模型的预测精度较高。

基于ARCH族模型的股票超高频数据的波动性研究——以浦发银行为例

论文基于浦发银行股票的逐笔交易数据,利用ARCH族模型对其超高频数据中的波动性进行了研究。论文首先通过对数据的预处理和单位根检验,确保了数据的平稳性,随后应用多种ARCH族模型对波动性进行建模与比较,最终选择TGARCH(2,1,1)模型作为最优模型。该模型不仅能够捕捉数据中的波动集聚效应,还揭示了显著的波动非对称性。研究结果表明,浦发银行的股票收益波动性具有显著的持久性和杠杆效应,负面冲击对波动的影响大于正面冲击。基于这些发现,论文提出了加强高频交易监管、优化投资策略和强化风险管理等政策启示。

基于椭球体理论粘性土层隧道松动土压力研究

准确预测隧道上覆土压力对隧道支护结构的设计和开挖方式的选择具有重要意义.Terzaghi土拱效应理论是基于滑移面为垂直面这一假设建立的,但实际情况中由于受到地层扰动的影响,滑移面呈现出曲面形状.为研究粘性土层滑移面演化规律及松动土压力分布规律,首先,采用数值模拟软件计算隧道开挖后上覆土压力,并分析粘性土下土拱效应演化规律;其次,根据隧道拱的破裂面规律,从椭球体理论出发,并考虑粘性土层中主应力轨迹线为圆弧对Terzaghi松动土压力进行修正;最后,将理论计算结果与已有的实验数据及有限元计算结果进行对比,验证了本文公式在粘性土层中应用的合理性,并进一步研究了地层损失率S_(L)、内摩擦角φ、黏聚力c与隧道松动土压力的关系.研究结果表明:相较于无粘性土层,粘性土层滑移面的破坏程度更大,但两者滑移面变化规律基本一致.当隧道埋深比H/D≤1.5,出现三角形状滑移面,随着隧道埋深的持续增大,地层逐渐向内形成剪切面,最终形成塔形状滑移面;松动区内部侧土压力系数K_(v)在任意位置处都是不同的,且在Terzaghi建议的1.0上下浮动.对比浅埋隧道,深埋隧道的松动土压力受地层损失率S_(L)的影响更大.粘性土层隧道上覆荷载呈“半葫芦形”分布,表现为从拱顶附近向拱腰逐渐减小;同时,在内摩擦角φ较小的地层中,提高黏聚力c有利于减小隧道上覆土压力.