Desert ecological control and ecological industrial construction: Practice and inspiration from China

Desertification poses significant threats to the ecological security and sustainable economic and social development of countries worldwide. In China, existing desertified land primarily lies between 35°–50°N, covering arid and semi-arid regions and a total area of 1.688×106 km^(2), which represents 17.58%of the total territorial area of the country (Fig. 1).

Investigation of FRP and SFRC Technologies for Efficient Tunnel Reinforcement Using the Cohesive Zone Model

Amid urbanization and the continuous expansion of transportation networks,the necessity for tunnel construction and maintenance has become paramount.Addressing this need requires the investigation of efficient,economical,and robust tunnel reinforcement techniques.This paper explores fiber reinforced polymer(FRP)and steel fiber reinforced concrete(SFRC)technologies,which have emerged as viable solutions for enhancing tunnel structures.FRP is celebrated for its lightweight and high-strength attributes,effectively augmenting load-bearing capacity and seismic resistance,while SFRC’s notable crack resistance and longevity potentially enhance the performance of tunnel segments.Nonetheless,current research predominantly focuses on experimental analysis,lacking comprehensive theoretical models.To bridge this gap,the cohesive zone model(CZM),which utilizes cohesive elements to characterize the potential fracture surfaces of concrete/SFRC,the rebar-concrete interface,and the FRP-concrete interface,was employed.A modeling approach was subsequently proposed to construct a tunnel segment model reinforced with either SFRC or FRP.Moreover,the corresponding mixed-mode constitutive models,considering interfacial friction,were integrated into the proposed model.Experimental validation and numerical simulations corroborated the accuracy of the proposed model.Additionally,this study examined the reinforcement design of tunnel segments.Through a numerical evaluation,the effectiveness of innovative reinforcement schemes,such as substituting concrete with SFRC and externally bonding FRP sheets,was assessed utilizing a case study from the Fuzhou Metro Shield Tunnel Construction Project.

Research on the Application of Intelligent Construction Technology in Hangzhouxi Railway Station

Relying on the construction management of Hangzhouxi Railway Station,this paper analyses the comprehensive application of intelligent construction technology and the establishment of the common data environment(CDE)by using BIM technology.This paper gives the idea that such issues are deeply explored as large-span curved surface structure improvement,steel structure construction monitoring,special-shaped ticket check canopy construction,prefabricated machine room construction,grid construction management,etc.so as to form an intelligent construction management system based on BIM technology.The system has achieved good application results in economic benefits,social benefits and environmental benefits,which can promote the gradual transformation to a more digitalized,networked and intelligent Hangzhouxi Railway Station,and lay a solid foundation for achieving the construction goals of controllable construction period,excellent quality,green and low carbon,etc.

Consideration of the Application and Risk Prevention of VAT Tax Rebate Policy for Construction Enterprises at the End of the Period

The“Announcement on Deepening the Value-Added Tax Reform”clearly outlines the preferential policy regarding incremental retention tax rebates.With the advancement of value-added tax(VAT)reform and the improvement of VAT legislation in China,VAT tax planning for construction enterprises,particularly related to retained tax credits,has become routine.This paper,focusing on the characteristics of construction enterprises,analyzes VAT retained tax credits at the end of the period,the status of tax refunds,practical issues,and related processes,and offers suggestions for policy application and risk prevention.

Analyzing the Form-Finding of a Large-Span Transversely Stiffened Suspended Cable System: A Method Considering Construction Processes

The precise control of the shape of transversely stiffened suspended cable systems is crucial. However, existing form-finding methods primarily rely on iterative calculations that treat loads as fixed known conditions. These methods are inefficient and fail to accurately control shape results. In this study, we propose a form-finding method that analyzes the load response of models under different sag and stress levels, taking into account the construction process. To analyze the system, a structural finite element model was established in ANSYS, and geometric nonlinear analysis was conducted using the Newton-Raphson method. The form-finding analysis results demonstrate that the proposed method achieves precise control of shape, with a maximum shape error ranging from 0.33% to 0.98%. Furthermore, the relationships between loads and tension forces are influenced by the deformed shape of the structures, exhibiting significant geometric nonlinear characteristics. Meanwhile, the load response analysis reveals that the stress level of the self-equilibrium state in the transversely stiffened suspended cable system is primarily governed by strength criteria, while shape is predominantly controlled by stiffness criteria. Importantly, by simulating the initial tensioning process as an initial condition, this method solves for a counterweight that satisfies the requirements and achieves a self-equilibrium state with the desired shape. The shape of the self-equilibrium state is precisely controlled by simulating the construction process. Overall, this work presents a new method for analyzing the form-finding process of large-span transversely stiffened suspended cable system, considering the construction process which was often overlooked in previous studies.

Thoughts on the Development of Bridge Technology in China

In the history of bridge engineering, demand has always been the primary driving force for development. Driven by the huge demand for construction since China’s reform and opening-up, Chinese bridge has leapt forward both quantitatively and qualitatively in three major stages, by completing the transition from “follower” to “competitor,” and nally to “leader.” A new future is emerging for Chinese bridge engi- neering. As an important part of China’s transportation infrastructure, the bridge engineering industry is facing challenges in this new era on how to support the construction of a new form of transportation. This paper provides a summary of the status of bridge technology in China, based on a basic analysis of stock demand, incremental demand, and management demand. It is our belief that the Chinese bridge engi- neering industry must ful ll three outstanding requirements: construction ef ciency, management effec- tiveness, and long-term service. Intelligent technology based on information technology provides a new opportunity for innovation in bridge engineering. As a result, the development path of bridge engineering needs to be changed. This paper puts forward the idea of developing a third-generation bridge project that is characterized by intelligence, and discusses this project’s implications, development focus, and plan. In this way, this work provides a direction for the improvement of the core competitiveness of China’s bridge engineering industry.

Construction Technology of Roof Membrane for World Cup Main Stadium

Based on the installation of the roof membrane of Lusail Stadium which is the main stadium of Qatar World Cup in 2022, a series of key technical challenges in the design and construction of the roof PTFE membrane of large stadiums are studied. Based on the analysis of the roof cable net system, the study formulated the overall sequence of membrane installation, and defined the construction method of membrane lifting and unfolding. Focusing on membrane fixing techniques with the tension rings, compression rings, and horizontal cable nodes, it also optimized membrane connection methods with arch and horizontal cable, and provided waterproof construction methods. According to the findings, the construction of stadium roof membranes should follow a logical sequence. The membranes’ fixing, connection and waterproof construction will have an important impact on the final quality.

Key Construction Technology of Super Large Diaphragm Wall Reinforcement Cage

The longest reinforcement cage of the Shenzhen LNG Receiving Station’s underground continuous wall is 59.5 m,and the total lifting weight is more than 110 t.It is a super large reinforcement cage,which is extremely tough to construct and lift.The quality of reinforcement cage processing is guaranteed by adopting the mold frame and a reasonable processing procedure.Feasible technical scheme and quality and safety assurance measures are put forward from the aspects of site layout,hoisting equipment selection,hoisting point layout and hoisting process control to ensure the safe implementation of super large underground continuous wall reinforcement cage hoisting operation.Combined with the project example,the construction challenge of super large underground continuous wall reinforcement cage is solved by adopting the construction technology of integral fabrication and hoisting.

Key Construction Technology of Ultra-deep Diaphragm Wall Under Complicated Geological Conditions

The LNG Receiving Station project in Shenzhen is located in a land reclamation area with complicated geological conditions.The thickness of diaphragm wall is 1.5 m,the depth is up to 62 m,and is extremely difficult to construct.During the construction process,slot wall reinforcement technology is used to ensure the stability of slot formation,and milling-drilling-milling technology is used to address the problem of ultra-deep rock of diaphragm wall.The super-large reinforcement cage of underground continuous wall is built and lifted in one time to ensure the construction quality and safety,and the green construction is achieved by adopting the green and environment-friendly mud circulation treatment technology.The construction technology of ultra-deep diaphragm wall applied in the project yielded positive results and has the potential be become more widely used.

Is Green Infrastructure Viable for Mitigating Pluvial Floods?A Retrospective Study of a Community Renovation Applying LID Principal and Practice in Zhenjiang City of China

Is GI(Green Infrastructure)viable to mitigate urban pluvial flood caused by extreme storm events?Limited research and planning have been undertaken in recent years,but little practice has been found in the real world.This retrospective study provides an example of mitigating pluvial flood by LID(Low Impact Development)principal and practices and transforming an old,ultra-dense low-income community into a climate change resilient community.The key findings include keeping flood control in mind when designing GI in the beginning;mimicking the sites’hydrologic characteristics as much as possible;outreaching to residences for maintenance issues from the beginning and monitoring the performance of GI facilities continuously.Technically,bioretention growing media with higher infiltration rate is specified that must be great than 150 mm/h in short term and 80 mm/h for long term;this paper chose low maintenance permeable pavement products avoiding clogging;and increasing parking space without compromising the design goals.

Experimental research and energy analysis of a new type of dry ice powder pneumatic rock breaking technology

When the traditional drill and blast method is applied to rock crushing projects,it has strong vibration,loud noise and dust pollution,so it cannot be used in densely populated areas such as urban public works.We developed a supercritical CO_(2)true triaxial pneumatic rock-breaking experimental system,and conducted laboratory and field tests of dry ice powder pneumatic rock-breaking.The characteristics of the blast-induced vibration velocity waveform and the evolution of the vibration velocity and frequency with the focal distance were analyzed and discussed.The fracturing mechanism of dry ice powder pneumatic rock breaking is studied.The research results show that:(1)The vibration velocity induced by dry ice powder pneumatic rock breaking decays as a power function with the increase of the focal distance;(2)The vibration frequency caused by dry ice powder pneumatic rock breaking is mainly distributed in 1–120 Hz.Due to the dispersion effect,the dominant frequency of 10–30 Hz appears abnormally attenuated;(3)The traditional CO_(2)phase change fracturing energy calculation formula is also applicable to dry ice pneumatic rock breaking technology,and the trinitrotoluene(TNT)equivalent of fracturing energy is applicable to the Sadovsky formula;(4)Dry ice powder pneumatic rock breaking is shock wave and highenergy gas acting together to fracture rock,which can be divided into three stages,among which the gas wedge action of high-energy gas plays a dominant role in rock mass damage.

Systematic Research and Innovation Practice on New Concepts of Construction for Xiong'an Railway Station

As the first major transport infirastructure in Xiong'an New Area,Beijing-Xiong an Intercity Railway is an important step for China State Railway Group Co.A Ltd.to quickly implement the major strategic plan of CPC Central Committee and the State Council.for the establishment of Xiong'an New Area.Xiong'an Station with double-floor spacious waiting areas and the wonderfiul integration of overpass and station building is the first modern integrated transport hub of this kind in China.Based on the characteristics of Xiong'an Station and in the light of the relevant new theories,methods and technologies,systematic studies and innovative practices on the new concept of building up a"well-connected,filly-integrated,environmen-frindly,passenger-oriented,economically-efficient,uurally-rich,intelligent and convenient"passenger station are carried oul,which achieve good results of application and help accumulate valuable experiences for the construction of passenger stations of Chinese high-speed railways in the new era.

Application of GNSS-PPP on Dynamic Deformation Monitoring of Offshore Platforms

The real-time dynamic deformation monitoring of offshore platforms under environmental excitation is crucial to their safe operation.Although Global Navigation Satellite System-Precise Point Positioning(GNSS-PPP)has been considered for this purpose,its monitoring accuracy is relatively low.Moreover,the influence of background noise on the dynamic monitoring accuracy of GNSS-PPP remains unclear.Hence,it is imperative to further validate the feasibility of GNSS-PPP for deformation monitoring of offshore platforms.To address these concerns,vibration table tests with different amplitudes and frequencies are conducted.The results demonstrate that GNSS-PPP can effectively monitor horizontal vibration displacement as low as±30 mm,which is consistent with GNSS-RTK.Furthermore,the spectral characteristic of background noise in GNSS-PPP is similar to that of GNSS-RTK(Real Time Kinematic).Building on this observation,an improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN)has been proposed to de-noise the data and enhance the dynamic monitoring accuracy of GNSS-PPP.Field monitoring application research is also undertaken,successfully extracting and analyzing the dynamic deformation of an offshore platform structure under environmental excitation using GNSS-PPP monitoring in conjunction with improved CEEMDAN de-noising.By comparing the de-noised dynamic deformation trajectories of the offshore platform during different periods,it is observed that the platform exhibits reversible alternating vibration responses under environmental excitation,with more pronounced displacement deformation in the direction of load action.The research results confirm the feasibility and potential of GNSS-PPP for dynamic deformation monitoring of offshore platforms.

A Simplified Method for the Stress Analysis of Underground Transfer Structures Crossing Multiple Subway Tunnels

According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer structure spanning multiple subway tunnels was proposed.Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model.The resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer structure.The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels.The established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate action.The pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.

Rheological properties and concentration evolution of thickened tailings under the coupling effect of compression and shear

Cemented paste backfill(CPB)is a key technology for green mining in metal mines,in which tailings thickening comprises the primary link of CPB technology.However,difficult flocculation and substandard concentrations of thickened tailings often occur.The rheological properties and concentration evolution in the thickened tailings remain unclear.Moreover,traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties.An experiment of flocculation condition optimization based on the Box-Behnken design(BBD)was performed in the study,and the two response values were investigated:concentration and the mean weighted chord length(MWCL)of flocs.Thus,optimal flocculation conditions were obtained.In addition,the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear,compression,and compression-shear coupling experimental conditions were tested and compared.The results show that the shear yield stress under compression and compression-shear coupling increases with the growth of compressive yield stress,while the shear yield stress increases slightly under shear.The order of shear yield stress from low to high under different thickening conditions is shear,compression,and compression-shear coupling.Under compression and compression-shear coupling,the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases,while concentration increases slightly under shear.The order of concentration from low to high under different thickening conditions is shear,compression,and compression-shear coupling.Finally,the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.

Regression Method for Rail Fastener Tightness Based on Center-Line Projection Distance Feature and Neural Network

In the railway system,fasteners have the functions of damping,maintaining the track distance,and adjusting the track level.Therefore,routine maintenance and inspection of fasteners are important to ensure the safe operation of track lines.Currently,assessment methods for fastener tightness include manual observation,acoustic wave detection,and image detection.There are limitations such as low accuracy and efficiency,easy interference and misjudgment,and a lack of accurate,stable,and fast detection methods.Aiming at the small deformation characteristics and large elastic change of fasteners from full loosening to full tightening,this study proposes high-precision surface-structured light technology for fastener detection and fastener deformation feature extraction based on the center-line projection distance and a fastener tightness regression method based on neural networks.First,the method uses a 3D camera to obtain a fastener point cloud and then segments the elastic rod area based on the iterative closest point algorithm registration.Principal component analysis is used to calculate the normal vector of the segmented elastic rod surface and extract the point on the centerline of the elastic rod.The point is projected onto the upper surface of the bolt to calculate the projection distance.Subsequently,the mapping relationship between the projection distance sequence and fastener tightness is established,and the influence of each parameter on the fastener tightness prediction is analyzed.Finally,by setting up a fastener detection scene in the track experimental base,collecting data,and completing the algorithm verification,the results showed that the deviation between the fastener tightness regression value obtained after the algorithm processing and the actual measured value RMSE was 0.2196 mm,which significantly improved the effect compared with other tightness detection methods,and realized an effective fastener tightness regression.

On the Preparation of Low-Temperature-Rise and Low-Shrinkage Concrete Based on Phosphorus Slag

The effects of different contents of a MgO expansive agent and phosphorus slag on the mechanical properties,shrinkage behavior,and the heat of hydration of concrete were studied.The slump flow,setting time,dry shrinkage,and hydration heat were used as sensitive parameters to assess the response of the considered specimens.As shown by the results,in general,with an increase in the phosphorus slag content,the hydration heat of concrete decreases for all ages,but the early strength displays a downward trend and the dry shrinkage rate increases.The 90-d strength and dry shrinkage of concrete could be improved with a phosphorus residue content between 0%-20%,with the best performances in terms of mechanical properties and shrinkage characteristics being achieved for a content of 20 kg/m^(3).On the basis of these results,it can be concluded that appropriate amounts of phosphorus slag and MgO expansive agent can be used to improve the compressive strength of concrete in the later stage by reducing the hydration heat and dry shrinkage rate,respectively.

Frost Resistance of Pervious Concrete Mixed with Waste Glass Powder

The contents of waste glass powder(WGP)(0%,10%,15%,20%,25%)and water-binder ratio(W/C)(0.24,0.26,0.28)were used as influencing factors,and the quality loss rate(Δm)and compressive strength loss rate(Δfc)were used as characterization parameters.The Ca/Si ratio and main element contents of C-S-H gels with different WGP content were investigated by energy dispersive spectrometry(EDS).The pore structure evolution characteristics of WGP composite cementing materials were investigated by low field nuclear magnetic resonance(NMR).UsingΔfc as the index of frost resistance degradation and Weibull function,the frost resistance degradation of glass doped pervious concrete(WGP-PC)was modeled.The results show that,with WGP,for the same number of cycles,Δm andΔfc decrease and increase with the increase of WGP.Under the same WGP content,Δm andΔfc decrease first and then increase with the increase of W/C.After 100 freeze-thaw cycles,the samples with WGP content of 20%and W/C of 0.26 have the best freeze-resistance.Microscopic tests show that with the increase of WGP content,the Ca/Si ratio of C-S-H gel decreases at first and then increases with the increase of WGP content.The extreme value of Ca/Si is 2.36 when WGP is added by 20%.The pore volume of hardened paste with 20%WGP content decreased by 18.6%compared with that of cement system without WGP.The overall compactness of the specimen was improved.On the basis of the test data,a life prediction model was established according to Weibull function.The experiment showed thatΔfc could be used as a durability degradation index,and the slope of the reliability curve became gentle after WGP was added,which reduced the damage degradation rate of PC.W/C was 0.26.It's about 5000 hours.

Influence of Polyaluminum Chloride Residue on the Strength andMicrostructure of Cement-Based Materials

In this paper,cement and dechlorinated Polyaluminum Chloride Residue(PACR)have been used to prepare a net slurry and mortar specimens.Two hydration activity indicators have been used to quantitatively analyze the dechlorinated PACR hydration activity.In particular,the effect of dechlorinated PACR content on the compressive strength of mortar has been assessed by means of compressive strength tests.Moreover,X-ray diffraction(XRD)and scanning electron microscopy(SEM)have been employed to observe the microstructure of the considered hydration products.The following results have been obtained.The 28th day activity index of the dechlorinated PACR is 75%,and therefore it meets the criterion for the use of active admixture.The increase in the content of the dechlorinated PACR tends to reduce the compressive strength of mortar specimens,however,it is beneficial to its later strength growth.When the content is not greater than 10%,the strength remains unchanged,otherwise,it decreases.The PACR does not form a new crystalline phase in the cement slurry,and the dechlorinated PACR remains active until the age of the 28th day.The inclusion of the PACR mainly deteriorates the early strength of the cement slurry,but it promotes the production of hydration products in the cement slurry after the 7th day.

Exploring the feasibility of prestressed anchor cables as an alternative to temporary support in the excavation of super-large-span tunnel

Excavating super-large-span tunnels in soft rock masses presents significant challenges.To ensure safety,the sequential excavation method is commonly adopted.It utilizes internal temporary supports to spatially partition the tunnel face and divide the excavation into multiple stages.However,these internal supports generally impose spatial constraints,limiting the use of large-scale excavation equipment and reducing construction efficiency.To address this constraint,this study adopts the“Shed-frame”principle to explore the feasibility of an innovative support system,which aims to replace internal supports with prestressed anchor cables and thus provide a more spacious working space with fewer internal obstructions.To evaluate its effectiveness,a field case involving the excavation of a 24-m span tunnel in soft rock is presented,and an analysis of extensive field data is conducted to study the deformation characteristics of the surrounding rock and the mechanical behavior of the support system.The results revealed that prestressed anchor cables integrated the initial support with the shed,creating an effective“shed-frame”system,which successively maintained tunnel deformation and frame stress levels within safe regulatory bounds.Moreover,the prestressed anchor cables bolstered the surrounding rock effectively and reduced the excavation-induced disturbance zone significantly.In summary,the proposed support system balances construction efficiency and safety.These field experiences may offer valuable insights into the popularization and further development of prestressed anchor cable support systems.