Construction Parameters Research Articles

Hole Wall Stability Analysis of Long-Distance Pipeline Horizontal Directional Crossing

Trenchless technology is a new technique for laying, repairing, and replacing underground pipelines in recent years, but various field accidents are often caused by the failure of hole wall in the process of trenchless construction, which leads to trenchless engineering accidents. Stress and deformation around hole are calculated by theoretical calculation. The numerical calculation method is also used to research the stability of hole wall with different diameters, buried depth, and soil parameters, and the curves of stress and deformation are fitted. The results show that stress and deformation of hole wall increase with the increase of the diameter. Under the condition of shallow burial depth, stress and deformation increase with the increase of burial depth of hole. The stress and deformation are different with different Poisson’s ratio and elastic modulus. This research has a new understanding for the instability of hole wall caused by variations of external parameters, which has important guiding significance for the selection of construction parameters and trenchless path.

Analysis of flexural failure mechanism of ultraviolet cured-in-place-pipe materials for buried pipelines rehabilitation based on curing temperature monitoring

Flexural properties is one of the important parameters for the evaluation of buried pipeline ultraviolet cured-in-place pipe (UV-CIPP) rehabilitation effectiveness. The flexure failure mechanism of UV-CIPP materials under the influence of different construction parameters (curing time, UV lamp irradiation intensity, curing distance, and material thickness) is unclear. In this paper, a method was proposed to approximate evaluation of the curing quality by monitoring the surface temperature of UV-CIPP material during the curing process. The flexure failure process and the causes of flexure failure of UV-CIPP materials were analyzed by considering the effects of construction parameters, combined with the monitored material surface peak temperature, and using a three-point bending test incorporating HD video and SEM observations, and sensitivity analysis of construction parameters was carried out by using random forest, and the flexural properties of UV-CIPP materials were predicted by support vector machine. The results showed that matrix cracking, debonding delamination and fiber pull-out fracture are the main reasons for the flexural failure of UV-CIPP materials. Under the influence of a single variable, the exothermic temperature of curing reaction on the surface of UV-CIPP material increases with the increase of curing time, UV lamp power and material thickness within a certain range, and decreases with the increase of curing distance. With the increase of curing time, UV lamp irradiation intensity and curing distance within a certain range, the flexural strength and flexural modulus show a trend of first increase and then decrease, but gradually decrease with the increase of material thickness. The monitoring and analysis results of the curing reaction exothermic temperature show that curing time and UV lamp irradiation intensity are still important factors affecting the curing performance of the material, and the flexural properties of the pipeline UV-CIPP material and the surface curing reaction exothermic temperature satisfy a nonlinear decreasing function relationship, and excessive curing reaction temperatures can reduce the flexural properties of UV-CIPP materials and accelerate its flexural failure.

Study on the influence of constructional parameters on performance of outer layer of thermal protective clothing

A study was designed to determine the effect of basic construction parameters of woven fabric on the thermal protection and comfort performance of the fabric. Thermal protection performance may be calculated using thermal protective performance (TPP) rating. The thermal resistance and water vapour transmission rate (WVTR) of different fabric woven patterns were used to evaluate their comfort performance. The current research is primarily concerned with determining the influence of fabric weaving pattern (plain, twill 2/2, twill 3/1, satin and honeycomb), picks per inch (40, 50 and 60), ply of yarn (2 ply and 3 ply) and type of material (meta aramid and para aramid). We measured the TPP rating of fabrics against 50:50 combination of radiant heat and flame exposures at high level of heat flux (80 ± 2 kW/m2 or ∼2 cal/cm2/s). It was found that the TPP rating of honeycomb weave was very good for the same picks per inch compare to other weaves. The change in ply of yarn (from 3 ply to 2 ply) reduce the TPP rating and areal density of fabric but % loss in areal density is higher compare to TPP rating. Comparing honeycomb woven fabrics to fabrics with different weaving pattern, thermal resistance of honeycomb woven fabrics were good. As the number of fabric picks per inch increased for each type of woven structure examined, the TPP rating and thermal resistance improved, while WVTR declined. The multiple linear regression equation (model) is significant for TPP rating.

Influence of Small Radius Curve Shield Tunneling on Settlement of Ground Surface and Mechanical Properties of Surrounding Rock and Segment

Compared with straight tunnels, over-excavation occurs on the inner side of the curved section during shield construction of small radius curved tunnels, and the disturbance to the ground surface and mechanical properties of surrounding rock and segment are more severe. This paper establishes the numerical models of small radius curve tunnels and straight tunnels to study the characteristics of surface deformation caused by the shield excavation of small radius curved tunnels and the influence of shield construction parameters on ground settlement, surrounding rock deformation, and segment force. The maximum error between the numerical simulation results and the measured surface settlement curve is 7.3%, which is in good agreement. The results show that: (1) The maximum value of the surface settlement of the small radius curve tunnel appears inside the curve section, and with the decrease in the curve radius, the surface settlement increases, and the distance between the peak settlement point and the tunnel center is larger. (2) When the curve radius of the tunnel is smaller, the lateral displacement of the ground surface moves farther to the inner side, and the range of soil mass with lateral displacement in the inner side is also wider. (3) Increasing the heading face pressure and grouting pressure can reduce surface settlement, but the heading face pressure should not exceed 350 kPa, and the grouting pressure should not exceed 250 kPa. (4) When the curve radius is smaller, the deformation of surrounding rock and the segment stress is larger.

Analysis and CFD Modeling of Thermal Collectors with a Tracker System

Thermal solar systems are currently one of the most suitable ways to convert solar radiation into usable energy. To ensure maximum energy gain, it is necessary to correctly adjust the direction of the collectors in the southern direction. The deviation from the south is energy acceptable, but there are losses that reduce the overall efficiency of the system. A suitable tool for increasing the efficiency of solar thermal collectors is the usage of tracker systems which track the position of the Sun along the ecliptic orbit. The system is directed south towards the equator. It is important to know the effectiveness of the system in terms of assessment. For the monitored period of the equinox, the increase of the solar thermal gain of the system with rotation of the collectors represents 16.23%. One of the methods is to use simulation tools to simulate different conditions of solar energy flow. A model in the Ansys software was developed for solar thermal flat collectors. The model is based on setting the material parameters of the collector construction, the properties of the absorber in terms of absorption as well as the materials and its geometry, the properties of the heat transfer medium, and the setting of the volume flows. At the same time, it is possible to define the change in the energy flow of the incident radiation. The model is a useful tool for evaluating collectors used by different tracking systems. The model was experimentally verified on a tracker system and compared with experimental data with good agreement. For sunny days, the model shows an accuracy rate of 98.7% in the condition without rotation, and 99.1% in the condition with rotation of the collector. After including the 5% degree of uncertainty for the condition of the rotated collectors, the accuracy of the model is 94.2% and for the condition without rotation 93.8%.

Numerical simulation of the effect of water-decoupling charge blasting on reservoir permeability enhancement

In the development of deep resources, blasting fracturing technology is one of the most effective means to improve the permeability of otherwise low-permeability reservoirs, while the pressure rise time of shock wave and the charge structure are the key factors affecting the blasting effect. Thus, this paper first deduces a formula for the pressure rise time, based on which, the blast-induced damage evolution is numerically simulated, and the numerical result is consistent with the existing studies, which verifies the feasibility of the formula. In addition, the influence of decoupling coefficients (K) of different types of explosives (i.e. TNT, emulsion, and ANFO explosives) on the damage range of reservoir blasting is studied. It is found that under the blasting of different types of explosives, the damage evolution law of the reservoir is different, and appropriate explosives should be selected in combination with rock stratum parameters in actual construction. Finally, the increase in permeability and the drainage effect of the reservoir after blasting are quantified by numerical simulations. It is demonstrated the average permeability increment of the reservoir under the action of TNT explosive is the largest, which is 3.08 (K = 4), while that under the action of emulsion explosive and ANFO explosive are 1.49 (K = 2) and 1.17 (K = 3) respectively; and the changes in reservoir permeability and drainage volume are coherent with the range of damage; the greater the range of damage, the greater the reservoir permeability and the greater the drainage efficiency.

CFD Analysis of a Round Shaped Air Cushion Vehicle with Flexible Skirt Segments at 90° Part I: Different Positions of Bag to Cushion Feed Orifice

Abstract Air cushion vehicles represent an interesting research area, mainly from their application point of view. But, at the same time, represents the reason of the scarcity of published results. Based on a series of initial simulations carried out by authors, which analysed lift forces for a round-shaped air cushion vehicle where the segments of the flexible skirt were inclined at 90˚, it was decided to carry out more complex studies regarding this configuration, presented in a series of articles. This complex study consists in performing static CFD simulations, in which values for different constructive elements are modified in order to analyse their influence on lift force. In this first article, the imposed fixed parameters are: angle of inclination of the segments of the flexible skirt and height of the segments, respectively. The main constructive variable parameters are: air clearance height and length between the edge of the bag to cushion feed orifice and inner wall of the flexible skirt segments. The simulations were carried out in ANSYS Fluent software, where velocity contours, streamlines and velocity profiles from the exit under the flexible skirt were analysed and through Curve Fitting Toolbox application found in MATLAB program, the equations were established that describe lift force variation.

Stability Analysis and Construction Parameter Optimization of Tunnels in the Fractured Zone of Faults.

In order to improve the construction method of highway tunnel fault, improve the excavation level, improve the construction efficiency, reduce the project cost, and shorten the construction period, so as to find a specific road, this paper puts forward the research method of tunnel stability analysis and construction parameter optimization in the fault fracture zone. First, this paper analyzes the specific geographical and geological environment of the construction site. Second, this paper compares and analyzes the effects of the drilling and blasting method and full-face tunnel boring machine (TBM) in construction and further analyzes the surrounding rock deformation, over excavation, and under excavation, as well as the range of loose circles when the surrounding rock is stable. Then, this paper discusses the minimum smooth blasting parameters under these conditions. Finally, the actual blasting effect of tunnel construction is tested and the optimization algorithm model of tunnel fault drilling and blasting parameters is established. The results show that the proposed optimization model of drilling and blasting construction parameters for highway tunnel faults based on the Support Vector Regression (SVR) algorithm combined with a genetic algorithm (GA) has a short calculation time and high parameter optimization accuracy. It is very feasible to optimize the construction parameters of the fault drilling and blasting method, which can greatly improve the construction efficiency, carry out the detailed simulation, reduce the cost, and increase safety. In summary, it has a certain reference significance for the optimization of highway tunnel construction and future research by drilling and blasting method under complex geological conditions in my country.

DETERMINATION OF THE RANGE OF SPEED REGULATION OF WORKING BODIES OF THE MECHANISM FOR SEPARATION OF STEM FEEDS BY MATHEMATICAL MODE

The issue of increasing the efficiency and reducing the energy consumption of the technological operation of unloading stem fodder (silage and haylage) from trench storage by block-batch method, due to the development and justification of parameters and modes of operation of the adaptive hydraulic drive system. Recommendations for determining the range of speed control of the working bodies of the mechanism for separation of stem forages on the basis of the developed system of hydraulic actuators of the separator mechanism with maintenance of energy saving mode of the pumping station and investigated nonlinear mathematical models mechanism and features of functioning of executive hydraulic motors of drives of the cutting mechanism in the mode of adaptation to real character of process of separation of a stalk forage. According to the results of mathematical modeling rational values of parameters of the developed hydraulic system of the mechanism for separation of a stalk forage corresponding to area of steady work of system are established, influence of components of hydraulic units of system of hydraulic drives of the separator mechanism regulation of speeds of the working bodies which are put in action by executive hydraulic motors. Based on theoretical and experimental studies, it was found that reducing the width of the working edges of the spool leads to the most effective expansion of the technological range of speed control of the separation mechanism driven by the hydraulic motor - cutting mechanism and hydraulic cylinder - drive P - shaped frame. As a result of research of influence of parameters of the developed hydraulic system of the mechanism for separation of stem forages on the range of technical regulation of speed of working bodies, constructive and technological parameters of the developed hydraulic drive are revealed. Determining the most optimal values of these parameters will increase the sensitivity and efficiency of the proposed hydraulic drive mechanism for the separation of stem forage. According to the results of the research, recommendations for the choice of structural and technological parameters of the developed hydraulic system of the mechanism for the separation of stem forages are provided.

Detailed Microkinetics for the Oxidation of Exhaust Gas Emissions through Automated Mechanism Generation

Emissions from vehicles contain a variety of pollutants that must be either oxidized or reduced efficiently in the catalytic converter. Improvements to the catalyst require knowledge of the microkinetics, but the complexity of the exhaust gas mixture makes it challenging to identify the reaction network. This complexity was tackled by using the “Reaction Mechanism Generator” (RMG) to automatically generate microkinetic models for the oxidation of combustion byproducts from stoichiometric gasoline direct injection engines on Pt(111). The possibilities and the limitations encountered during the generation procedure are discussed in detail. A combination of first-principles-based mechanism construction and top-down parameter refinement allows a description of experimental results obtained by kinetic testing of a Pt/Al2O3 monolith under stoichiometric conditions. The study can serve as a blueprint for the usage of RMG for other challenging heterogeneously catalyzed reactions.

Dynamics of semiflexible generalized scale-free polymer networks

We study the relaxation dynamics of a new type of hyperbranched polymer networks, which are constructed using a degree distribution specific to scale-free networks. The topology of the constructed networks is controlled through three parameters: γ, which measures the density of links in the network, the minimum allowed degree Kmin and the maximum allowed degree Kmax. The static properties of the polymers are investigated through the mean square radius of gyration. We study the dynamics in the framework of the generalized Gaussian structures model by monitoring in detail the influence of networks’ construction parameters, namely γ, Kmin, and Kmax, and the stiffness parameter q on the relaxation quantities: averaged monomer displacement, storage modulus and loss modulus. In the intermediate (time or frequency) regions of the dynamical quantities we encounter a scaling behavior for γ=2.5 and usually a non-scaling behavior for other values of γ. Switching on the stiffness parameter q one is able to destroy, create or enlarge some scaling regions for other combinations of the parameters. Another way to widen a scaling region is to slightly increase Kmin.

Mechanism and Numerical Simulation of Vertical Fracture Propagation in Composite Coal Rock

Vertical fracture propagation mechanism is important to understand the effect of hydraulic fracturing on the roof of outburst coal seams. In this paper, the differences in physical parameters and in situ stress between an outburst coal seam and its roof strata were compared, and influencing factors of roof-fracturing fractures connecting coal seams were vertically analyzed. The impact of different fracturing strata and injection rates on fracture propagation was studied by numerical models. Results show that the horizontal principal stress of an outburst coal seam is less than that of roof strata, and the fracture length of roof fracturing is larger than that of an outburst coal seam. Roof-fracturing fracture of an outburst coal seam has the material conditions to communicate downward with the coal seam. The downward propagation height of roof-fracturing fracture is positively correlated with the minimum horizontal stress difference between an outburst coal seam and its roof strata. Soft coal fracturing cannot form a long fracture dominated by tensile failure, so the coal seam can be communicated by transforming the roof strata of soft coal to form vertical fractures. The injection rate affects the failure location, fracture width, and fracture-propagation path of the numerical model. Construction parameters should be reasonably designed in accordance with the physical parameters of coal and rock, construction displacement, and in situ stress. These research results can provide a theoretical basis and data support for the design, and optimization of construction parameters of roof fracturing in outburst coal seams.

Construction the Image of Akademgorodok: Elements and Structure

The article is devoted to the study of the construction of the image of the Novosibirsk Academgorodok as a hierarchical structure consisting of certain elements. As an empirical object, young residents of Akademgorodok aged 18 to 35 years, both visitors and locals, were chosen. This study is located at the intersection of such areas of sociology as sociology of a city and visual sociology, the study provides an overview of modern sociological studies of the city and classical theories of sociology. The first chapter presents an overview and analysis of the sociological research devoted to the study of a city and approaches to understanding and identifying the image of urban space, and also formulates the main objectives of the study. Thus, the first chapter is the theoretical and methodological basis of our study. The second chapter is a description of the research methodology and contains a description of the empirical object and information base of the study, as well as data collection methods. Data collection was carried out applying two methods: online survey and interview. For each method, a toolkit has been developed — a questionnaire and an interview guide. The data collected by the online survey method made it possible to describe the context of living conditions in the Novosibirsk Academgorodok through the description of subjective assessments of satisfaction with living conditions, and the online survey also served as a way to recruit informants for interviews. After collecting data through semi-formalized interviews, the main conclusions are made and the results of the study are described. The parameters of the language construction of the image of Academgorodok were described, the types of visual images of Akademgorodok were identified, and the territorial identity was described as an emotional connection with the place.

Mechanical Performance of Deep Circular Caisson Sinking in Deep Layered Soft Soil

In order to study the mechanical behavior of open caisson foundation in the Wenzhou area, combined with the characteristics of the soil layer in the Wenzhou area, based on the field measurement and investigation of a wide range of engineering cases, this project studies the mechanical properties of open caisson sinking in soft soil stratum and optimizes the construction parameters through the combination of field measurement, numerical simulation, and theoretical calculation, while ensuring the smooth sinking of the open caisson, control the deformation effect of the soil around the open caisson to serve the urban construction. The research results can directly serve the whole process of design, construction, measurement, and control of open caisson engineering. It has engineering practical significance and can be used as a reference for similar projects.

Simulation of a Temperature-Compensated Voltage Sensor Based on Photonic Crystal Fiber Infiltrated with Liquid Crystal and Ethanol.

A simulated design for a temperature-compensated voltage sensor based on photonic crystal fiber (PCF) infiltrated with liquid crystal and ethanol is presented in this paper. The holes distributed across the transverse section of the PCF provide two channels for mode coupling between the liquid crystal or ethanol and the fiber core. The couplings are both calculated accurately and explored theoretically using the finite element method (FEM). The influence of voltage on the alignment of the liquid crystal molecules and confinement loss of the fiber mode are studied. Liquid crystal molecules rotate which changes its properties as the voltage changes. As the characteristics of the liquid crystal will be affected by temperature, therefore, we further fill using ethanol, which is merely sensitive to temperature, into one hole of the PCF to realize temperature compensation. The simulated results show that the sensitivity is up to 1.29977 nm/V with the temperature of 25 °C when the voltage ranges from 365 to 565 V. The standard deviation of the wavelength difference is less than 2 nm within the temperature adjustment from 25 to 50 °C for temperature compensation. The impacts of the construction parameters of the PCF on sensing performances of this voltage sensor are also analyzed in this paper.

Construction parameters of graded sand-gravel foundation on seismic response law of nuclear safety grade underground corridor

The treatment of soft soil foundation under nuclear safety grade corridors with graded sand and gravel materials has a good development prospect. It is of great engineering value to explore the influence of construction parameters of graded sand and gravel foundation on the seismic response of gallery structures. Taking the safety grade underground corridor of a nuclear power plant as the engineering background, the equivalent linear method is used to consider the nonlinear dynamic characteristics of graded sand and gravel. The energy transfer boundary is applied at the truncation boundary to simulate the dissipation effect of scattered wave fluctuation energy and the ground motion input. The thicknessless contact element is introduced to consider the contact effect between the corridor structure and the graded sand and gravel foundation, so as to establish the calculation model of the dynamic interaction between the graded sand and gravel foundation and the corridor structure. Furthermore, the influence of the relative compactness and the foundation treatment depth on the seismic response of the corridor structure is studied, and the calculation results of the acceleration response spectrum and relative displacement of the corridor structure are analyzed. The calculation results show that the two construction parameters have different degrees of influence on the seismic response of corridor structure. The research results can provide reference for the engineering design and construction of underground corridors, and provide technical support for the application of graded gravel materials in soft soil foundation treatment.

Multi-Factor Design for a Vacuum Ejector Improvement by In-Depth Analysis of Construction Parameters

A vacuum supersonic ejector is an indispensable pneumatic device placed in nearly all industrial production lines. This device, also called a zero-secondary flow ejector, is characterized by the maximum entrained flow and the minimum secondary pressure. Numerical simulations were carried out by means of the CFD toolbox OpenFOAM v8 and its solver HiSA, which uses the AUSM+up upwind scheme. A single-factor analysis of eight parameters was performed to find how the ejector’s performance was enhanced or decreased, while other parameters were fixed. Four parameters were subject to further analysis to find the geometry that improves the standalone performance of the ejector. The mixing chamber length is the parameter that most improves its performance; alone it leads to a 10% improvement. A multi-factor analysis, based on a fractional factorial design, is carried out with the four relevant parameters. Results indicate that the multi-factor analysis enhances the performance of the ejector by 10.4% and the mixing chamber length is the factor that most influences the improvement. Although a multi-factor design improves the performance, no significant relevance has been detected with respect to the mixing chamber length improvement alone. The improved performance of this device leads to a reduction in operating time and, as a consequence, results in significant energy savings.

IMPACT OF DESIGN PARAMETERS ON THE NATURAL VENTILATION OF A FAMILY HOUSE ATTIC FROM SANTA FE (ARGENTINA)

The roof of a family home introduces important amounts of heat into the house. In Santa Fe city (Argentina), the attic of social family houses is not designed with thermal optimization purposes. In this work, a low Reynolds number k-e turbulent model is computationally implemented to show that a proper selection of constructive parameters of a vented attic leads to a great reduction of the heat transferred from the roof to the ceiling. The main physical consequence of a vented attic is the existence of a convective flow barrier close to the roof that carries important amounts of heat from the attic out to the environment. It is shown that the heat transferred through the ceiling to the interior of the house can be reduced in more than 70 % for summer conditions. Roof pitch and attic volume are also explored.

Analysis of Rebound Rate of Wet Shotcrete Based on Experiment and Discrete Element Method

Wet shotcrete support is the main support method for underground engineering construction at present. The rebound rate is one of the indicators to evaluate the support effect, and a lower rebound rate will improve the construction effect of wet shotcrete. The concrete aggregates available in different regions of China have different particle sizes. To achieve better supporting effect, the discrete element method is used to simulate the spraying process of wet shotcrete. By constructing the nozzle structure and simplifying the concrete structure, the paper establishes the discrete element model of wet shotcrete. Using the above model, the paper analyzes the effects of injection distance and shrinkage angle on the injection rebound rate of concrete with three aggregate sizes of 5∼11 mm, 11∼17 mm, and 17∼25 mm. The optimal construction parameters of concrete with different aggregate particle size ratios were obtained through simulation experiments. The simulation results are highly consistent with the field experimental structure. It is feasible to simulate wet shotcrete spraying process by the discrete element method.

Long-Term Thermal Stress Analysis and Optimization of Contraction Joint Distance of Concrete Gravity Dams

Results of the conducted research aiming to demonstrate the methodology of optimization of dam monolith length (distance between contraction joints), through monitoring the thermal tensile stresses during construction and service life of a concrete gravity dam that is built using the block method, are presented in this paper. A 3D space–time numerical model for phased thermal stress analysis is employed in a large concrete gravity dam case study. For the adopted block dimensions, schedule, and dynamics of construction and material parameters, the thermal stress analysis is conducted, taking into account the following: thermal physical properties of the material, the cement hydration process, heat exchange with the external environment and the reservoir, and self-weight of the structure. The main advantage of the proposed methodology is the possibility of controlling the cracks resulting from thermal tensile stresses in the monolith of a concrete gravity dam, by optimizing the monolith’s length to minimize the zones in which the tensile capacity of concrete is exceeded. The results obtained from the temperature field analysis show that the maximum temperature increase in the dam’s body results from the cement hydration process in combination with summer air temperatures in the construction phase. The aforementioned factors account for the increase in temperature of up to 45.0 °C, while during winter cooling of the structure occurs due to lower temperatures, especially in the surface zones. The results of the stress field analysis show that the extreme values of thermal tensile stresses are present in the process of a sudden or gradual cooling of the concrete when shrinkage occurs. Finally, it is shown that the reduction of the monolith length by 5.0 m (from 20.0 m to 15.0 m) results in a decrease in the extreme thermal tensile stress values by an average of 0.70 MPa (up to 12.0%) in winter and an average of 1.10 MPa (up to 20.0%) in summer; while for the entirety of the analyzed time period, results in a decrease in the extreme thermal tensile stress values by an average of 16.0% (0.93 MPa).