Abstract:Basic features of geo-materials generally show spatial variability to some extent due to their natural cause of formation. It's difficult to give a full description of the field basic features of geo-materials by use of limited testing data. The values of parameters which represent the basic features of geo-materials have great influence on the geotechnical engineering design. In this paper, a concept of genetic features for geo-materials is firstly proposed and definition as well as some attributes with regards to this concept are also given. Based on big data analysis and a large amount of data collected from practical projects in Chongqing, method for searching the genetic features of geo-materials is proposed. A software about the genetic feature analysis is developed and it can be used for collection, analysis and management of geo-materials data obtained from engineering practice. Based on it, more than 70 000 data about genetic features of typical geo-materials in Chongqing are collected and analyzed, some typical genetic maps of geo-materials in Chongqing are obtained.

Abstract:The reinforcement process was directly completed on the ring shear apparatus by remolding the shear box to reveal the strength characteristics of calcareous sandy samples during microbial treatment.The influence of treatment time on the curing effect was studied using ring shear tests. The effect of vertical stress was investigated. The results of treated samples were compared with those without treatment of calcareous sandy samples. The results showed that the treated samples with shorter treated time and relatively lower strength can be obtained utilizing completing the curing process on the modified ring shear apparatus directly. The shear strength of the treated samples increased and reached a constant with increase of treatment time. The shear strength and residual strength of the sample treated 48 hours could reach 1.8 times and 1.6 times of the values for untreated samples, respectively. Compared with the untreated sample, the treated sample shows obvious strain-softening behavior, which may be related to the destruction of the cemented structure of calcium carbonate. Under the condition of high vertical stress (75~125 kPa), both the treated and the untreated samples show an obvious strain-softening phenomenon, but the reasons behind this phenomenon are different.

Abstract:The unconfined compression test model of biocemented coral sand was established by discrete element software.The model simulates MICP cementation by generating tiny calcium carbonate particles on the surface and contact of the coral sand particles, considering the contact of coral sand-coral sand particles, coral sand-calcium carbonate particles and calcium carbonate-calcium carbonate particles. The microscopic characteristics of biocemented coral sand with different cementation degrees, such as particle displacement, micro-crack development, and micro-crack distribution, were analyzed, which better explained the macroscopic deformation and failure mechanism. Results show that in case of unconfined compression, large displacement and failure occur at both ends of the material, while displacement in the middle part is small. The micro-crack development during the sample loading process can be divided into three stages, namely the compaction stage, the crack propagation stage and the rapid growth stage.With increase of the degree of cementation, the failure of the sample change from large pieces to small pieces or scattered particles, and the ratio of the number of tensile and shear cracks decreases, the difference of the number of microcracks decreases in all directions, and the crack propagation is more uniform.The proposed model can better simulate the cementation of MICP, and lay foundation for full understanding of the macroscopic deformation and failure mechanism of biocemented coral sand.

Abstract:The stress-fractional plasticity model has been proposed to model the state-dependent stress-strain behavior of granular soils. However, the previous model was established based on triaxial test, which cannot be easily used to predict the three-dimensional (3D) stress-strain characteristics of rockfill. To solve this problem, an attempt is made to modify the fractional plasticity model for rockfill by using a novel concept of characteristic stress to make the model capable of predicting the 3D stress-strain behavior of rockfill. A series of true triaxial test results of rockfills under different initial states are simulated, from which a good agreement between the model predictions and the corresponding testing results is found. Comparing with the classical plasticity model, no additional plastic potential is required; in addition, the model can describe 3D strength characteristics by mapping from the characteristic stress space to the normal stress space, where no specific 3D strength criterion is needed.

Abstract:The inclined long short composite pile has the advantages of good deformation control ability and low cost. Currently, there are limited studies on this aspect and understanding of its working mechanism is still lacking. In view of this, through the model test and numerical method, the deformation and mechanical characteristics of long and short inclined piles under different inclination and pile length combinations during excavation are studied, and then the working mechanism is discussed. The results show that: For inclined long short composite piles, the supporting effect is directly proportional to the inclination angle and inversely proportional to the pile length of row piles, and the influence of inclination angle is the greatest, followed by the pile length; When the total pile length is fixed and the short pile meets a certain embedded depth, the inclination angle has a critical value. When the inclination angle is less than the critical value, the optimal pile length distribution is affected by the inclination angle. When the inclination angle is greater than the critical value, the longer the inclined pile, the better the supporting effect.

Abstract:The purpose of this study is to perform a complete finite element (FE) simulation of the suction bucket foundation in clay using advanced soil constitutive model to establish the failure envelope of the suction bucket foundation. Firstly, the Hardening Soil (HS) model is used to analyse the centrifuge tests of suction bucket foundation in normally consolidated clay under different monotonic combined loadings by FE method. The comparisons between testing and simulated results verify the effectiveness of the FE analysis using the HS model. Then, a large number of FE analysis is performed by radial swipe tests, and further extended to the failure mode of V-H-M (vertical force-horizontal force-bending moment) space. Based on this, the failure envelope on the H-M plane, the V-H plane, and the three-dimensional failure envelope surface in the V-H-M space are described. The results show that the H-M failure envelope is similar to an inclined ellipse; the effect of vertical load on the inclination of the H-M failure envelope can be ignored; the size of the H-M failure envelope decreases with the increase of the vertical load; there is a strong interaction between vertical and horizontal loads, i.e., the V-H yield surface formed by vertical and horizontal bearing capacity is approximately a quarter ellipse. It can be seen that the size of the H-M inclined ellipse is controlled by the vertical load. Based on all these results of numerical simulations, a new analytical expression is finally proposed to represent the three-dimensional failure envelope of the suction bucket foundation in V-H-M space.

Abstract:The dynamic resilience modulus of reinforced subgrade is an important design index of reinforced soil techniques in road engineering.In this paper, the dynamic resilience modulus test of geogrid-reinforced gravel soil was carried out by dynamic triaxial apparatus, and the influence pattern of water content, reinforcement mode, the shear and lateral influence characterization in the dynamic resilience modulus were comparatively analyzed.The prediction model parameters for dynamic resilience modulus were analyzed by regression. Experimental results showed that the dynamic resilience modulus of reinforced soil reduced with increase of moisture content.The geogrid should be laid in the horizontal shear deformation layer in the soil, the dynamic resilience modulus could be considerably improved by increasing the number of reinforcement layers or reducing the spacing of layers.When other conditions remained unchanged, the dynamic resilience modulus increased with the increase of shear and lateral influence characterization. The parameter regression results of the NCHRP 1-28A model were satisfactory, the model could be used to predict the dynamic resilience modulus of geogrid-reinforced reinforced soil.

Abstract:In Guangxi province, the expansive soil is widely distributed, and the damage to the project is relatively great. It is essential to improve it. Using manufactured sand and water glass as modifiers, in this study, the expansive soil in Nanning, Guangxi was improved under the condition of mixing them separately or in combination. The strength and stiffness of the expansive soil were measured by unconfined compression test and direct shear test. It was found that both manufactured sand and water glass can improve the strength and rigidity of the expansive soil, and both the strength and rigidity first increase and then decrease with increments of the manufactured sand and water glass amount. The manufactured sand will reduce the improvement effect of water glass in the case of compound mixing. The optimum addition amount of water glass is 1%, the optimum addition amount of manufactured sand is 10%. The expansive soil was further improved with manufactured sand of different particle sizes, and it was found that in order to improve the strength of the expansive soil, the particle size of the manufactured sand should not be greater than 0.5 mm. This study verifies the effectiveness of water glass modified expansive soil and manufactured sand instead of natural weathered sand to improve expansive soil, which can provide a reference for future improvement of expansive soil.

Abstract:In the actual bamboo structures, the column base is usually subjected to tensile load. In view of this, a kind of bamboo bolt connection with embedded wood was proposed. Therefore, the axial tensile test of 15 bamboo bolt connection specimens with embedded wood was designed. Firstly, the yield load and yield displacement of specimens were determined according to 50% of the maximum capacity of Karacabeyli-Ceccotti, and then the characteristics of different deformation stages in the load displacement curve were evaluated. Finally, the influence of bolt diameter and screw hole end distance on the bearing capacity and failure mode of these connection specimens was analyzed. The results showed that the connection has a certain bearing capacity and deformation capacity, and the bearing capacity increases with increase of screw diameter. The load-displacement curve of the connection has two elastic segments in tension, and the stiffness decreases in the second elastic stage. The three failure modes include screw bending, bamboo wall punching shear and bamboo wall cracking. The failure mode is controlled by screw hole end distance and screw diameter. The formula derived from the simplified mechanical model can approximately predict the bearing capacity of the joint.

Abstract:Based on analysis of the bearing capacity of the bolted connections for bamboo scrimber,the applicability of the wood structure design codes in calculating the bearing capacity of the bolted connections for bamboo scrimber was evaluated. A total of 48 specimens in 16 groups designed by orthogonal scheme were tested in this study. Firstly, the applicability of Foshci's theory model was verified. Then, the effects of bolt diameter, end distance and main component thickness on the bearing properties of bolt connections were analyzed. Finally, the accuracy of design codes GB 50005 and European 5 in calculating the bearing capacity of the bolted steel-BS-steel connections was evaluated. The result showed that Foschi's theory model could reflects the change characteristics of both the linear elasticity and post-yield phases, which also expressed depicted the whole bearing processes of the connections, comprehensively. The bearing capacity is affected by bolt diameter, main component thickness and end distance, and it is affected by the bolt diameter most obviously when the connection meets the minimum requirements of size design. Besides, Eurocode 5 is so conservative in calculating the bearing capacity of the bolted steel-BS-steel connections. There is a safety reserve in calculating the bearing capacity by GB 50005, which is more suitable for calculating the bearing capacity of the bolted steel-BS-steel connections than Eurocode 5.

Abstract:This article mainly studies a recyclable fully assembled steel-concrete composite beam, which is composed of several precast concrete slabs and a steel beam through a new type of shear connector (hereinafter referred to as "fastener").The fastener is fixed on the steel channel beneath the concrete slab. Moreover, the shear force between the steel beam and the prefabricated concrete slab is transmitted through the friction between those two. In order to study the flexural performance of this new fully assembled steel-concrete composite beam under static load, six sets of full-scale specimens were subjected to four-point bending tests under simply supported conditions. The six sets of test pieces are all partially shear connections, including five groups of recyclable fully assembled steel-concrete composite beams and one group of cast-in-place composite beams with studs as shear connectors. The main variablesare the number of precast concrete floor slabs and the distance between loading points. The test results show that the composite beam exhibits a certain combination effect under monotonic load. The larger greater the number of prefabricated plates, the lower the initial stiffness of the specimen, but it has no obvious effect on the ultimate flexural capacity of the specimen. The length change of the pure bending section has no significant effect on either the initial stiffness nor the ultimate flexural capacity of the specimen.

Abstract:This paper proposed a novel modular steel structure system, which arranges the improved module units at interval and integrates them with the coupled unit, to avoid the structural redundancy resulting from the laminated-beams and group-columns.In view of the assembly characteristics of the novel structural system, this paper further proposed a beam-column joint, which connects the beams on both sides separately through fully-welded connection and fully-bolted connection. To investigate the seismic behavior of novel joint, quasi-static tests of three full-scale cruciform joint specimens were carried out, the failure modes, hysteretic curves, envelop curves, stiffness degradation and energy dissipation capacity of joints were analyzed, the effect law of vertical-splicing bolt connection type and column wall thickness in panel zone on the seismic behavior of joint was discussed. The results show that, seismic behavior on both sides of joint specimens exhibit some differences.The hysteresis curves of the coupled side joint are in bow shape and have good rotation behavior, the modular side joints exhibit shuttle shape hysteretic curves but their rotation ability are poor. Thickening the column wall in panel zone is an effective way to improve the seismic behavior of the joint.High strength bolts applied in vertical splicing could improve the hysteretic behavior, stiffness and energy dissipation capacity of the coupled side joint compared with through high-strength bolts.

Abstract:In order to find out the influence of the number of key groups of precast-assembled nail group connector on the mechanical properties of shear keys, the push-out loading tests of single key group and double key group are carried out. The load-slip curve, failure form and shear capacity of the group specimens, combined with the numerical simulation of the three-bond group and four-bond group specimens, are used to study the bearing capacity reduction effect of the assembled shear key under the multi-bond group. The results show that the failure modes of the single bond group and the double bond group shear bond are both stud shearing, however, the number of cracks of the single bond group specimen is less than that of the double bond group specimen. The force inhomogeneity between bond groups gradually becomes obvious with the increase of load.Meanwhile, it is the fact that the distribution of the slip along the height direction is larger than that of the upper part, and the minimum slip of the interface is about 67% of the maximum, showing obvious inhomogeneity.The reduction effect of bearing capacity increases with the increase of the number of bond groups, and the reduction of double bond group, three bond group and four bond group relative to single bond group are 0.84, 0.80 and 0.72 respectively.Based on the energy method, the bearing capacity reduction effect of multi bond group due to uneven force is analyzed, and a simplified formula of bearing capacity reduction factor is proposed,which is in good agreement with the finite element calculation results.

Abstract:In order to systematically study the influence of multi-parameter combinations on the seismic performance and establish a reliable numerical analysis model of circular reinforced concrete piers, a quasi-static orthogonal test of four-factors and three-level for circular reinforced concrete bridge piers has been carried with pier height ( shear span ratio ), longitudinal reinforcement ratio, axial compression ratio and stirrup ratio as factors.Then the skeleton curve and hysteretic behavior of specimens were simulated with fiber model and equivalent plastic hinge model using OpenSees platform. The results show that all test piers have good seismic performance,the displacement ductility is between 5.3 and 8.4, and the equivalent viscous damping ratio is between 0.19 and 0.29. At the level of confidence of 0.1, the pier height and longitudinal reinforcement ratio have a greater influence on the ultimate displacement, the aspect ratio and longitudinal reinforcement ratio have a significant effect on the maximum lateral load, the longitudinal reinforcement ratio has a significant impact on the cumulative energy, the aspect ratio and axial load ratio have a greater impact on the equivalent stiffness, and the aspect ratio is negatively correlated with the maximum lateral load, the rest are all positively correlated. The force-displacement relationship curves of bridge piers derived from the fiber element model agree well with experimental results.Both numerical simulation of the section-level and component-level based on equivalent plastic hinge model can be used as an effective method to evaluate the seismic performance of reinforced concrete bridge piers.

Abstract:In order to study the mechanical properties of concrete-filled glass fiber reinforced polymer (GFRP) tubular short columns under single axial compression and repeated axial compression under different reinforcement modes, twelve two-identical specimens of concrete-filled GFRP tubular short columns were produced. And the concrete-filled GFRP tubular short columns were reinforced by carbon fiber reinforced polymer (CFRP) cloth in different ways. Based on the test results, the failure mode, load carrying capacity of columns, deformation capacity, reinforcement effect, stress-strain curve, relationship between plastic residual strain and unloading strain and limit state of specimens were analyzed. It shows that the ultimate strength of the specimens in three reinforcement modes is improved greatly; there is a linear relationship between the plastic residual strain and the unloading strain of the specimen before and after reinforcement, and the slope of the straight line increases with the strengthening of the restraint. Modifying the FRP-confined concrete loading and unloading model proposed by Lam et al. Predicting the unloading path of CFRP-reinforced GFRP pipe concrete composite short columns by the modified model under repeated axial compression in different reinforcement modes. After comparing, it shows that the test results agree well with the modified model.

Abstract:Ring section is a common form of section in engineering structure, but there exists double nonlinearity (nonlinearity of material and section width) in reinforcement calculation of concrete ring section.In the Code for Design of Concrete Structures, only the transcendental equations for the calculation of uniform reinforcement are given, which require programming and iterative solution and cannot be calculated manually, which is very inconvenient.In addition, some ring section members (such as high bridge piers, precast pipe piles, etc.) have long length, large section size and large amount of reinforcement. If uniform reinforcement is adopted, the reinforcement stress near the neutral axis is small and the economy is poor.If asymmetrical reinforcement is adopted, the stress reinforcement is arranged in the peripheral area far away from the neutral axis, which can make full use of the strength of concrete and reinforcement to improve economic benefits.Based on the constitutive relation between concrete and steel, this paper determines the range and boundary of strain variation and starts from strain.By analytical method, stress is solved by strain, and then internal force is calculated without iteration.Finally, the calculated results are drawn into a Nomo-diagram that is convenient for manual calculation of reinforcement, which is fast and convenient for calculation, and suitable for C50 or below strength concrete and annular sections with arbitrary diameters.

Abstract:Coal gasification wastewater is difficult to treat by conventional biological processes due to the high load of recalcitrant organic matter and high toxicity. In this study, a growth promoting agents and bacterial consortia were used to enhance the treatment efficiency of secondary effluent from coal gasification wastewater, and the microbial mechanism of the bioaugmentation was discussed. The results showed that an addition of crude oil degrading-bacteria has a significant positive effect on chemical oxygen demand (COD) removal from wastewater, in which the average COD removal rate during the first three cycles was increased by 19.7%, compared with the control group without bioaugmentation. In contrast, the addition of growth promoting agents can significantly reduce the COD concentration during the first cycle, but the strengthening effects is difficult to maintain for a long time. The average COD removal rate was increased by 21.5% by supplementing both crude oil-degrading bacteria and Tween 80 during the six cycles, compared with the control group without bioaugmentation. It showed that the combined addition of growth promoting agents and bacterial consortia has good stability and sustainability. Furthermore, a high-throughput sequencing analysis showed that the addition of growth promoting agents and bacterial consortia has little effect on dominant genus (such as Candidatus Competibacter and Defluviimona), but significantly increased the diversity of microbial communities. Limnobacter and Gaiella with high weight and closeness centrality are the keystone taxa in the coal gasification wastewater treatment system. Meanwhile, super pathways of vanillin and vanillate degradation are the key degradation pathways of microorganisms, indicating that the vanillin and vanillate may be the common degradation intermediates or their structural analogues of a variety of complex organic compounds in coal gasification wastewater.

Abstract:In order to solve the problem of "three sludges" in the treatment of oily wastewater from oil refinery, a strain GJ was isolated from the oily sludge of Daqing Oilfield, which can produced surfactant and degraded petroleum hydrocarbon. Through morphological observation, physiological and biochemical experiments and 16S rDNA sequence analysis, the strain GJ was identified as Shewanella sp.. The strain GJ was applied to the degradation experiment of scum and biochemical sludge, and the degradation kinetics of scum and biochemical sludge by GJ was discussed. After extraction and purification, TLC and FTIR analysis, it was confirmed that GJ product was a glycolipid surfactant. In the experiment of scum and biochemical sludge degradation, the degradation rate of petroleum hydrocarbon reached the highest, which was 81.11% and 83.21% respectively at the 7th day of strain GJ. Logistic growth model, Luedeking-Piret model and first-order reaction kinetics model can well simulate the growth of GJ cell, the synthesis of surface active products and the degradation of petroleum hydrocarbons. It is preliminarily inferred that GJ bacteria take petroleum hydrocarbon as carbon source, and secrete surfactant at the oil-water interface during the growth process, increase the contact degree between the strain and petroleum hydrocarbon, and promote the uptake and metabolism of petroleum hydrocarbon by GJ bacteria and self proliferation of GJ bacteria.

Abstract:Compared with conventional buildings, Construction of infectious disease hospitals needs to strictly control the surrounding wind environment and pollutant concentration, but the current research is highly scarce.This paper takes an infectious disease hospital under construction in Changsha as the case study. The detailed analysis of wind environment and pollutant dispersion of medical buildings under different thermal effects was conducted by a 10 m (width)×3 m (height) wind tunnel test. In the process, building layout and vegetation are considered.The results show that in the range of -0.23<Rb<0, the wind profile influenced by the thermal effect is mainly concentrated in the vertical component. However, the thermal effect will greatly affect the maximum value of flow field distribution. The absolute values of pollutant concentration are affected primarily by wind speed. The pollutant concentration is positively proportional to the local thermal effect with high wind speeds. In contrast, at low wind speeds the pollutant concentration increases first and then decreases with the local thermal effect and reaches the maximum value when Rb=-0.16. Changing the layout of the building is an effective way to improve the concentration of pollutants. When the direction of the building is consistent with the prevailing wind direction, it is most conducive to the emission of pollutant. The addition of vegetation in the building reverse flow area can promote the diffusion of pollutants, while the greenery in the ventilation corridor will inhibit the spread of contaminants.

Abstract:With a hot summer, cold winter and high humidity climate, residential energy consumption in the Yangtze River Basin is strongly affected by diverse air-conditioning behaviors in such a harsh indoor thermal environment. The development of big data technology provides a basis for larger samples, higher accuracy, and more dimensions of air-conditioning behavior monitoring, which can make up for the current situation of large errors in existing research methods and single classification indicators. By selecting 2 000 samples of residential room air conditioners (RACs) in Chongqing as the representative city: First, five characteristic parameters of air-conditioning operation are constructed from the perspective of air-conditioning using period, temperature demand and energy consumption; Then, a multi-dimensional clustering algorithm was used to identify the typical categories of air-conditioning behavior;Finally,through in-depth analysis of the characteristic differences among the clustering results, three typical air-conditioning behavior groups are summarized for residential buildings in Chongqing.

Abstract:The key variables of building HVAC energy consumption are the few decisive variables among all the variables that may influence the energy consumption of building HVAC energy consumption. The HVAC key variables are important for the two commonly used energy consumption prediction models (namely white box model and black box model). The modeling process of key-variables based energy prediction is greatly simplified without excessively sacrificing accuracy compared with traditional way. The determination of key variables is a complicated process and is easily affected by the initial boundary conditions.A general identification method of key variable is proposed in this paper. The key variable are identified separately from HVAC load related variables and system related variables. This method applies both Morris method and regression method for key variable identification.Also an automatic key variable identification tool is developed based on Python and Eppy. This tool is applicable to all kinds of buildings in different climate zones. The case study shows that the key variables identified by the method proposed in this paper is able to accurately describe the variation and feature of HVAC energy consumption with a few variables.

Abstract:As a university-affiliated unit, student dormitories have many characteristics, such as large total building area, high utilization rates, and large total energy consumption. Existing research focuses on the electricity consumption analysis of the entire dormitory buildings, but lacks detailed analysis and research on the electricity consumption of each room in the student dormitory. In this study, 533 female dormitories of a university in Shanghai were divided into four types of electricity preferences, and the air-conditioning habits of students in the dormitories were investigated, and the relevant parameters affecting the electricity consumption of the student dormitories were analyzed.Research finds that student dormitory electricity preference is related to the length of time in winter the air conditioner is used. On the other hand, the regression analysis model shows that the electricity consumption of the same type of student dormitory has a linear relationship with the outdoor temperature.The case results show that the students' electricity preference and the average outdoor temperature obtained through clustering and segmentation are important parameters that affect the electricity consumption of the student dormitory. The method of obtaining the regression of these two parameters can effectively grasp the electricity consumption of the student dormitory.