Moisture Content Conditions Research Articles

Effect of vacuum environment on air side heat and mass transfer characters of plain fin-tube heat exchangers

Air-side heat and mass transfer performance of plain fin-tube heat exchangers at different vacuum degree have been experimentally investigated. In this experiment, influence of air inlet humidity on air-side heat and mass transfer under vacuum environment is studied by controlling vacuum degree and air inlet humidity. Results show that: variation trend of air-side sensible heat transfer coefficient (ha), heat transfer j-factor (jh), mass transfer coefficient (hm) and mass transfer j-factor (jm) are not all time remain the same. Variation trend of ha, jh are the same with increase of vacuum degree when air inlet humidity changes, ha is gradually decreased and jh is gradually increased. Variation trend of hm is opposite with the increase of vacuum degree when the air inlet humidity changes. Under constant air inlet relative humidity conditions, hm is gradually increased. Under constant air inlet moisture content conditions, hm is gradually decreased. However, variation trend of jm is the same with increase of vacuum degree when air inlet humidity changes, both are increased. But slope of jm is greater under constant air inlet relative humidity conditions. Overall heat transfer performance is greatly affected by air inlet humidity changes. Under constant air inlet relative humidity conditions, when air inlet relative humidity increases from 50% to 70% and then to 90%, proportion of latent heat transfer increases from 30.98%∼53.99% to 36.53%∼56.95% and then increases to 44.19%∼64.04% with vacuum degree increases. As proportion of latent heat transfer increases, air-side total heat transfer performance is not obviously reduced. Under constant air inlet moisture content conditions, when air inlet moisture content increases from 15 to 20 g/kg, proportion of latent heat transfer is basically unchanged with increase of vacuum degree, at about 36% and 37%, respectively. So, total heat transfer performance on air side decreases obviously. In order to model air-side heat and mass transfer performance of the complex structure fin-tube heat exchangers, a simplified model is investigated under vacuum environment. Results show that influence of pressure changes on heat and mass transfer based on theory is basically consistent with the results of regression analysis based on experimental results. This study can provide guiding suggestions for the design of heat exchangers under vacuum environment.

Simulation of air gasification of Napier grass using Aspen Plus

In this research, a thermodynamic equilibrium model was developed using Aspen Plus for parametric study of syngas composition and product yield from air gasification of Napier grass in a fluidized bed gasifier. Operating conditions of gasification encompassing temperature, pressure, equivalence ratio (ER), and moisture content were manipulated and studied with further validation against experimental data. Tar cracking reaction was considered with M-cresol and heptane as represented species. Conversion of homogenous reactions was empirically correlated in MATLAB and further utilized to adjust the composition of CO, H2 and CH4 for prediction of experimental data with better accuracy, where the average mean error ranges from 0.20 to 0.25. Maximum lower heating value (LHV) was attained at 750 °C, contributed by the highest CH4 composition. ER change had limited effect on bioliquid yield but showed a significant contribution in lowering biochar yield. Lowering moisture content improved syngas quality significantly through the promotion of CO, H2 and CH4 production, with minimum biochar and bioliquid yield. The optimized LHV were 7.69 MJ/Nm3 at T = 750 °C, ER = 0.2 and moisture content of 4.5 wt%.

Drought could promote the heartwood formation in Dalbergia odorifera by enhancing the transformation of starch to soluble sugars

ABSTRACT The heartwood of Dalbergia odorifera T. Chen (D. odorifera) is highly valuable. It was speculated that drought could promote heartwood formation in D. odorifera. To test this hypothesis, we artificially simulated conditions of low and high soil moisture content and investigated whether D. odorifera trees living in habitats with contrasting soil water conditions display distinct heartwood formation. Besides, we performed a preliminary study to explore the possible mechanism of drought affecting heartwood formation in D. odorifera in terms of non-structural carbohydrates (NSC). Higher heartwood formation percentage and heartwood size were observed in drought-treated trees. The heartwood density of drought-treated trees was significantly greater than that of control and the oil content of heavy drought-treated heartwood was significantly higher than that of the other treatments. None of water treatments had a significant effect on the essential oil components of heartwood. Furthermore, the effects of water treatments on the total amount of NSC were very limited; however drought treatments enhanced the transformation of starch to soluble sugars compared to control. This study confirmed the hypothesis that drought could promote the heartwood formation in D. odorifera, not by changing the total amount of NSC but by changing the component proportion of NSC.

겉보리의 발아조건 및 혼합발효를 이용한 효소 및 베타글루칸 생산 연구

The solid-state fermentation was carried out to produce enzymes and β-glucan using hulled barley with different germination time conditions and co-culture processes. The ergosterol concentration determined by high-performance liquid chromatography at UV 254 nm was used as a biomass indicator for fungal growth. Solid-state fermentation of hulled barley pretreated for 60 min at 121°C produced greater fungal biomass as well as increased concentrations of enzymes and β-glucan. The best germination time of solid-state fermentation was found to be 24 h. Maximum fungal biomass of 0.76 mg/g, amylase (23,293.10 U/g), protease (512.6 U/g), and β- glucan at 11.2% (w/w) were obtained during fermentation. Solid-state fermentation with co-culture was carried out using Aspergillus oryzaeNIBRFGC000501965 and Aureobasidium pullulans KCCM60122 to improve the β-glucan production. Maximum productions of fungal biomass, amylase, protease, and β-glucan were 1.26 mg/g, 33,206.89 U/g, 1,735.9 U/g, and 13.3% (w/w), respectively, at 60% of moisture content condition. Therefore, solid-state fermentation of hulled barley is a process that could enhance the yield and overall production of enzymes and β-glucan.

Effects of Neyraudia reynaudiana roots on the soil shear strength of collapsing wall in Benggang, southeast China

The collapse of collapsing walls is a key process during the Benggang development in southeast China and is closely related to the soil shear strength. Plant root reinforcement can effectively improve the soil shear strength. However, there are few studies on the effect of roots on the soil shear strength of collapsing walls. To explore the influence of roots on the soil shear strength of collapsing walls, the roots of Neyraudia reynaudiana was selected as the research object. This paper studies the tensile properties of the roots through root tensile tests and performs a direct shear test to study the influence of the roots on the soil shear strength by setting different mass moisture contents (15%∼30%) and root weight densities (0 ∼ 1.25 g 100 cm−3). Root tensile force is positively correlated with root diameter by a power function, while tensile strength is negatively correlated with diameter by a power function. Roots could increase the soil shear strength, and which was mainly reflected in cohesive force. The shear strength and cohesive force increase first then decrease with the increasing root density, while root density has no effect on the internal friction. The shear strength, cohesive force and internal friction of root-soil complex all decreased with increasing moisture content. The WWM (Wu and Waldron model) greatly overestimated the cohesion of herbaceous roots, and a new prediction model of the shear strength of root-soil composites was obtained by revising the WWM model by introducing the moisture content and root density (NSE = 0.94). In conclusion, Neyraudia reynaudiana roots could improve the soil shear strength, whereas the strengthening effect decreased under the condition of high moisture content. The results provide a basis for the selection and allocation of vegetation restoration measures in Benggang erosion in southern China.

Multifrequency electromagnetic geophysical tools for evaluating the hydrologic conditions and performance of evapotranspiration barriers

Surface barriers are designed to isolate subsurface contaminants for 1000 years or longer, functionally limiting water infiltration and removing the driving force for contaminant transport to groundwater. Cost-effective monitoring is challenging because of the long design life for surface barriers, spatial limitations and finite lifetime of in situ sensors, and performance metrics related to drainage. Hence, ground-penetrating radar (GPR) and electromagnetic induction (EMI) tools were evaluated for use in performance monitoring of surface barriers. GPR and EMI were used to non-invasively interrogate the Prototype Hanford Barrier (PHB), an evapotranspiration-capillary break barrier established in 1994 at the Hanford Site, in southeastern Washington State. Both geophysical methods were evaluated for providing indirect estimates of subsurface moisture content conditions that were compared to point scale measurements from borehole neutron logs. Surveys were performed during characteristically wet and dry periods to observe a range of hydrologic states of the barrier soil. Although EMI surveys were expected to show seasonal changes associated with changes in the bulk conductivity of the barrier soil layers, the effectiveness of the method was limited by the effects of metallic infrastructure embedded in the barrier. GPR estimates of volumetric water content were typically within 2–3% of the highest water contents from neutron probe measurements for both wet and dry periods, providing reasonable estimates of water content. Given that PHB monitoring data over the past 25 years has demonstrated its success in limiting deep drainage, GPR was found to be a cost-effective method for demonstrating continued barrier performance, with a greater capacity to quantify moisture content distributions over much larger areas relative to point measurements.

A Clustering Routing Algorithm for Wireless Sensor Monitoring Network in Irrigation Area

It is the basis for the implementation and scientific management decision of precision irrigation to accurately and comprehensively sense water and rainfall regime, soil moisture content and engineering conditions in irrigation areas and various environmental factors closely related to crop growth. In view of the characteristics of large monitoring range and scattered distribution of measuring points in the irrigation area, based on the analysis of the characteristics of the strip shape layout of the wireless sensor network at the water demand side of the irrigation area, and the limited battery energy and transmission distance under the condition of battery power supply, a clustering routing algorithm based on wireless sensor network for monitoring irrigation area is proposed (known simply as CRAIM algorithm). The formation of clusters, the selection of cluster heads, the routing process between clusters and the sink nodes are studied, and the CRAIM algorithm, EE-LEACH (energy-efficient LEACH) and MMH-LEACH (modified multi-hop LEACH) algorithm are simulated and compared respectively. Experimental results showed that, the new algorithm, CRAIM, has some advantages in the energy consumption of the network.

Discrete Element Simulation Based on Elastic–Plastic Damping Model of Corn Kernel–Cob Bonding Force for Rotation Speed Optimization of Threshing Component

Current corn kernel-cob bonding mechanics models (LSD models) uniformly consider the bonding force changes during the maize threshing operation as an elastic change, resulting in computational errors of up to 10% or more in discrete element simulations. Due to the inability to perform high-precision discrete element simulation of the mechanics characteristics during the corn threshing operation, the core operating parameters of the corn thresher (rotation speed of the threshing component) rely mainly on empirical settings, resulting in a consistent difficulty in exceeding 85% of the corn ear threshing rate. In this paper, by testing the mechanics characteristics of corn kernels, the bonding force is found to have both elastic and plastic changes during the threshing process. An elastic–plastic (EP) damping model of the corn kernel–cob bonding force was established by introducing a bonding restitution coefficient e to achieve an integrated consideration of the two changes. By testing the relationship between the properties of the corn ear itself and the model parameters, the pattern of the effect of the corn ear moisture content and the loading direction of the ear by force on the EP model parameters was found. By establishing a model of the relationship between the corn cob’s own properties and the model parameters, the EP model parameter values can be determined by simply determining the moisture content of the ear. In this paper, the EP model was established and the high-precision simulation and analysis of the process of bonding force variation between corn kernel and cob is realized on the self-developed AgriDEM software. At the meantime, the optimal values of the threshing component rotation speed under different conditions of moisture content of corn ear were obtained by establishing an optimization model of threshing component rotation speed. The test results showed that the corn ear threshing rate could reach more than 92.40% after adopting the optimized speed value of the threshing component in this paper. Meanwhile, the test results showed that the discrete element simulation results based on the EP model did not significantly differ from the measured results of the thresher. Compared with the most widely used LSD model, the EP model can reduce the computational error by 3.35% to 6.05%.

Experimental study on adfreezing strength at the interface between silt and concrete

The mechanical behavior of the interface between soil and structure is the key to determine freezing behaviors of pile foundations in cold regions. In order to explain the formation mechanisms of adfreezing strength at the soil-structure interface and explore its influencing factors and changing rules, orthogonal direct shear tests and orthogonal tensile tests were carried out under various conditions of moisture content, temperature, and dry density. Test data shows that: (a) The influence of moisture content and temperature on the shear and tensile strength is significant, while the influence of dry density is not. (b) The shear and tensile strength of the contact surface are positively correlated with the absolute value of the temperature and moisture content, but they exhibit different growth characteristics. (c) Under the same test conditions, when the tensile strength is less than 100 kPa, there is little difference in the shear and tensile strength of the contact surface. When the tensile strength exceeds 100 kPa, the tensile strength of the contact surface will be significantly greater than the shear strength. There is an exponential relationship between shear strength and tensile strength. Based on the experimental results, a bond-friction interface model which confirms the reliability of the model in simulating the mechanical behavior of the pile-soil interface is established. Research results clarify the mechanical behavior of the pile-soil interface at low temperatures, which can provide references for the interactive mechanisms of tapered pile-soil and the establishment of anti-freeze models.

Optimization of thermostable proteases production under agro-wastes solid-state fermentation by a new thermophilic Mycothermus thermophilus isolated from a hydrothermal spring Hammam Debagh, Algeria

The present work investigates for the first time the presence and isolation of the thermophilic fungi from hydrothermal spring situated at the locality of Guelma, in the Northeast of Algeria. The production of the thermostable proteases and the optimization of culture conditions under agro-wastes solid-state fermentation to achieve optimal production capacity were explored. A statistical experimental approach consisting of two designs was used to determine the optimum culture conditions and to attain the greatest enzyme production. Besides, different agricultural wastes were initially evaluated as a substrate, whereby wheat bran was selected for enzyme production by the isolate under solid-state conditions. The isolate thermophilic fungi were identified as Mycothermus thermophilus by sequencing the ITS region of the rDNA (NCBI Accession No: MK770356.1). Among the various screened variables: the temperature, the inoculum size, and the moisture were proved to have the most significant effects on protease activity. Employing two-level fractional Plackett–Burman and a Box–Behnken designs statistical approach helped in identifying optimum values of screened factors and their interactions. The analysis showed up 6.17-fold improvement in the production of proteases (~1187.03 U/mL) was achieved under the optimal conditions of moisture content 47%, inoculum 5 × 105 spores/g, and temperature at 42 °C. These significant findings highlight the importance of the statistical design in isolation of Mycothermus thermophilus species from a specific location as well as identifying the optimal culture conditions for maximum yield.

Rutting prediction models for flexible pavement structures: A review of historical and recent developments

Rutting is the major distress mode in flexible pavements occurring due to the repeated movement of traffic loading. Deformation in the pavements comprise of both recoverable (elastic) and irrecoverable (plastic) part. Overall deformation occurring in the flexible pavement system due to continuous vehicular movement is contributed from all the components of pavement. A number of empirical models have been proposed by several researchers for analysis and prediction of accumulated rutting in different components of pavement. The accumulated permanent strain has been expressed as the function of the number of load applications and deviator stress applications in most of the models proposed; however, factors such as stress state, moisture content, material type and environmental conditions also impose a significant influence on the permanent deformation characteristics of pavement materials under cyclic loading. In this article, a comprehensive review has been carried out covering every aspect of deformation related to distress occurring in pavements. Important rut models, modeling approaches and modern concepts in the rutting analysis of pavement structures have been presented. In addition to review, fallacy existing in the current design practices related to adaptation of stiffness parameters and negligence of shear strength aspect of subgrade soil has been also presented with the support of literatures. • Permanent strain along with resilient strain must be evaluated for accurate characterization of pavement materials. • Significant rut prediction models for pavement structure and subgrade soil have been discussed. • Limitation related to the adaption of stiffness parameters ( M R , CBR) in flexible pavement design.

Interaction of oxygen and moisture content on ‘Barton’ and ‘Jackson’ pecan storage

The effects of the nut moisture content (MC) and storage conditions on the physicochemical quality and volatile compound (VC) profile after storage of pecan nuts are still poorly understood. Therefore, the present study aimed to evaluate the effects of MC (6 and 4 %) and the interaction with atmospheric conditions (20.9 kPa) and low O2 partial pressure (2 kPa O2) on ‘Barton’ and ‘Jackson’ pecan storage. Color parameters, internal browning (IB) incidence and severity, respiration rate, acidity, peroxide value (PV), and VC profile after 8 and 12 months of storage at 20 °C were evaluated. ‘Barton’ and ‘Jackson’ pecans stored with 6 % MC + 2 kPa O2 presented the highest hue and luminosity (L) values, i.e. lighter color, after 8 and 12 months of storage. However, ‘Barton’ and ‘Jackson’ pecans stored with 6 % MC + 20.9 kPa O2 had the highest IB incidence and severity and respiration rate. After 8 months, pecans stored with 4 % MC + 20.9 kPa O2 had lower acidity and PV in both cultivars, compared with the pecans stored under 6 % MC + 20.9 kPa O2. The lower O2 in ‘Barton’ pecans stored with 6 % MC decreased PV, which was also the case for ‘Jackson’ nuts stored at 4 % MC. Regardless of the MC, pecans stored under 2 kPa O2 had the lowest hexanal and hexanol contents in both cultivars. Our findings suggest that it is necessary to choose between reducing MC or kPa O2 when aiming to maintain the quality of ‘Barton’ and ‘Jackson’ pecans stored under ambient temperature conditions (20 °C).

Investigation of the strength recovery characteristics of a red-bed landslide soil by SHS and ultrasonic experiments

The strength recovery (healing) of the shear zone soil of a landslide during the dormant phase after the sliding affects the reactivation of the landslide, and may play a key role in determining the stability of the landslide. In this paper, we report the laboratory measurements of frictional strengthening characteristics of a red-bed landslide soil. Slide-hold-slide (SHS) experiments and ultrasonic tests are performed on soil samples under natural moisture content and saturated conditions. The roles of holding time, normal stress, and drainage conditions in friction enhancement are evaluated. All the experiments are performed under room temperature. The saturated soil samples show the lowest recovery value of shear strength. It is found that red-bed landslides have obvious healing properties. The recovery value log-linear depends on the holding time and proportional to the normal stress, and the better the drainage condition is, the more obvious the recovery. Ultrasonic tests show that the wave speed difference of soil sample before and after holding is proportional to the holding time.

The Effects of Soil Moisture on Harvesting Operations in Populus spp. Plantations: Specific Focus on Costs, Energy Balance and GHG Emissions

Background: Poplar tree plantations for wood production are part of a worldwide growing trend, especially in moist soil sites. Harvesting operations in moist sites such as poplar plantations require more study for detailed and increased knowledge on environmental and economic aspects and issues. Methods: In this study, the effects of soil moisture content (dry vs. moist) on productivity, cost, and emissions of greenhouse gases (GHG) caused by operations of different harvesting systems (chainsaw-skidder and harvester-forwarder) were evaluated in three poplar plantations (two in Italy and one in Iran). Results: The productivity (m3 h−1) of both systems in the dry sites were significantly higher (20% to 30%) than those in the moist sites. Production costs (€ m−3) and GHG emissions (g m−3) of both systems in the dry sites were also significantly lower than those in the moist sites. The productivity of the harvester-forwarder system was about four times higher, and its production cost was 25% to 30% lower than that of the chainsaw-skidder system, but the calculated GHG emissions by harvester-forwarder system was 50–60% higher than by the chainsaw-skidder system. Conclusions: Logging operations are to be avoided where there are conditions of high soil moisture content (>20%). The result will be higher cost-effectiveness and a reduction in the emission of pollutants.

Effects of soy flour types and extrusion-cooking conditions on physicochemical, microstructural and sensory characteristics of puffed rice snack base

AbstractThe physicochemical properties of puffed rice snack base (PRSB) prepared via extrusion cooking under various feed moisture contents and screw speeds were investigated. The moisture content, screw speed, and soy flour type significantly (p < 0.05) affected the physicochemical properties of PRSB viz; size, density, porosity, color, breaking strength, crystallinity, water absorption index (WAI) and water solubility index (WSI). While, a slight effect on pasting properties was observed between PRSB added with defatted and full-fat soy flour, respectively. Soy flour lipids significantly (p < 0.05) influenced extrusion cooking conditions especially at high screw speed and feed moisture content. The result revealed that extrusion cooking with addition of full-fatty soy flour can be exploited as a viable method to produce PRS with a high expansion ratio and low breaking strength at recommended extrusion conditions of feed moisture content of 19 % and screw speed of 300 rpm.

Characteristics of Sludge and Associated Risk Assessment of Urban Sewage Treatment Plants

In urban solid waste management, the scientific and reasonable disposal and utilization of sewage sludge is becoming more and more important. It can be said that the pollution status and chemical properties of sewage sludge in urban sewage treatment plants can provide a basis for the scientific disposal and utilization of sludge. In this study, the characteristics of pH, moisture content, Cd, Cr, Cu, Zn, Pb, As, Hg, Ni, mineral oil, volatile phenol, PAHs, organic matter, nitrogen, phosphorus, and potassium were evaluated in sewage sludge collected from 49 sewage treatment plants in a certain city. The pollution status of heavy metals and organic pollutants, the frequency distribution of pollutant concentrations, and changes in the nutrient content were analyzed. The Nemero index and Hakanson potential ecological hazard index were used to assess the potential ecological risks of heavy metals in the agricultural utilization process of sludge. The results showed that under the condition of neutral pH values and high moisture content, the order of heavy metal content was Zn > Cu > Cr > Pb > Ni > As > Hg > Cd. The principal component analysis (PCA) results indicated that Cd, Pb, Hg, Ni, and As constituted the main load factors of the first main component of heavy metal sources. The most concentrated contents of 8 heavy metal frequency distributions among the 49 samples were 38.9-1380.0, 62.6-182.7, 63.6-181.3, 0.0-97.8, 19.3-68.4, 0.8-29.2, 0.3-8.7, and 0.01-0.96 mg·kg-1. In addition, the most concentrated frequency distribution of mineral oil, volatile phenol, and PAH concentration were 87.0%, 87.9%, and 77.6%, respectively. Moreover, the nutrient content of sludge was higher than the average level in China, and the organic matter content was 67.4%, 75.9%, and 92.5% of that of pig manure, cow dung, and chicken manure, while the content of nitrogen, phosphorus, and potassium was not very different. The Nemero index and Hakanson ecological hazard index results showed that the sludge of urban sewage treatment plant in the city has certain ecological risks. However, four sewage treatment plants were heavily polluted or highly ecologically hazardous among the 44 plants in this study, which were in line with the Standards for pollutant control of agricultural sludge. In summary, there are certain potential ecological risks for the agricultural utilization of sludge in the city, and it is necessary to reduce the heavy metal content before resourcing. More importantly, on the premise that the sludge meets the agricultural standards, a comprehensive ecological risk assessment is required to select a reasonable sludge recycling method.

Investigation of lightning damage mechanism and flashover channels on glazed roofing tiles of ancient buildings through laboratory experiments

Glazed roofing components play a very important role in Chinese ancient buildings. In this study, the artificial lightning strike test on a type of glazed roofing tile of ancient buildings in China was carried out to investigate the lightning damage mechanism of ancient buildings. A high-speed camera was used to observe the process of lightning striking the enamel, body and mortar of the glazed tiles. The highest propagation speeds of flashover channel are achieved on the enamel surface of the glazed tile, followed by one on the surface of the body and the mortar successively under the condition of the similar moisture content. The propagation speeds of flashover channels are generally positively related to the moisture content for the same material composition of the glazed tiles except mortar. The flashover channels are basically regular on the surfaces of the enamel and the body, while they are irregular on the surface of the mortar. For the enamel and the body of the glazed tile, the surface flashover is easier to develop along the rough body surface. The lightning current enters the glazed tile easily through the mortar position, which results in the fracture of the glazed tile. The reason might be related to the high porosity, high moisture content and good electrical conductivity of the mortar. So the mortar component of the glazed tiles should be important for the design of the lightning protection, which is helpful to decrease the lightning damage for the glazed roofing components.

Experimental Study on Mechanical Properties of Briquette Coal Samples with Different Moisture Content

Coal seam water injection is an important technical method to prevent and control coal and gas outburst and other disasters. Water can soften coal and change its mechanical properties. In order to study the mechanical properties of coal samples with different moisture content, briquette coal samples with five moistures content (4%, 6%, 8%, 10%, and 12%) were selected to carry out triaxial compression tests under different confining pressures (0.1, 0.2, 0.4, 0.8, and 1.2 MPa). Then, the mechanical response mechanism of the water-bearing briquette coal was analyzed. The results show that the slope of the linear elastic stage of the stress-strain curve gradually decreases with the increase of moisture content. Water-bearing coal exhibits strain strengthening characteristics under high confining pressure, which transforms the water-bearing coal from brittle to ductile state. The peak stress under different moisture content conditions shows a linear relationship with the confining pressure. The internal friction angle decreases linearly with the increase of moisture content. The cohesion varies parabolically with the increase of moisture content and reaches the maximum value when the moisture content is 8%. The coal body with moisture content between 7% and 9% has a high bonding force, which is beneficial to the consolidation of the coal body. Therefore, ensuring a reasonable moisture content of coal through coal seam injection can provide a basis for preventing coal and gas outburst.

An experimental study of the load carrying capacity of straight shaft and underreamed piles in expansive soil

This research aimed to determine and evaluate the load carrying capacity of underreamed piles embedded in expansive soils. Eight models of concrete piles were developed to examine the influence of piles’ bulb number and length on ultimate load carrying capacity. The piles used in this work had 20 mm stem diameters and 40 mm bulb diameters, and multi-layer soils (expansive soil above dense sand) were used. The piles used in the experiments were divided into two groups, each with four piles. The first group with l/d=14 had all piles embedded in the expansive soil layer and the pile’s tip set on dense sand while the other group, with l/d=24, had the pile stems embedded in the expansive soil and all bulbs in the dense sand. Experiments were then done under two conditions: optimum moisture content and soil completely saturated with water, with results that showed that the percentage of ultimate load carrying capacity increased in proportion to the l/d ratio on adding one bulb to a straight shaft pile and then increased slowly for piles with 2 or 3 bulbs in saturation conditions. The percentage of ultimate load carrying capacity increased similarly in optimum moisture content conditions. The results also showed a decrease in ultimate load carrying capacity between the two conditions of tests for piles with the same l/d and the same number of bulbs, however.

Effect of Veneer Initial Moisture Content on the Performance of Polyethylene Film Reinforced Decorative Veneer

The flexible modification of decorative veneer by plastic film is an effective method to broaden its applications. In order to understand the effect of initial veneer moisture content on the performance of plastic film reinforced decorative veneer, Fraxinus mandshurica veneers with different initial moisture contents were composited with polyethylene film. The overlaying performance of the decorative veneer and its interface morphology with MDF substrate were evaluated. The results showed that when the initial moisture content increased from 10% to 50%, the cavity proportion of PE film reinforced decorative veneer increased from 7.23% to 18.48%, while all of the minimum steel rod diameters remained at 7.6 mm. When the initial moisture content fluctuated between 10% and 20%, the optimum surface bonding strength (1 MPa) and immersion peel strength (0 mm) of the decorative veneer could be obtained. The strength of the decorative veneer significantly decreased when the initial moisture content was more than 20%, which was caused by the cavities and the poor interfacial bonding. The veneer surface was easy to crack under low moisture content conditions. Based on the overall performance and the cost of decorative wood-based panels, initial veneer moisture content was suggested to be 15% to 20%.