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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Inteligentní řídící metody v automatizaci procesů řízení stavebních strojů / Intelligent Control Methods in Automation of Process of Construction Machines Control

Vaverka, Michal January 2010 (has links)
This work deals with the possibility of use of intelligent methods in construction machines control. These methods are based on GPS in combination with using laser and ultrasonic technology. There is in detail described especially control by robotic total station and 3D control, which includes digital model of construction site. The new trends of control are especially applied on the vibratory rollers. There are taken into consideration: achievement of sufficient degree of compaction on the basis of on-line information about conditions of subsoil.
312

Recycling of concrete waste with wood waste through heating compaction

Liang, Li January 2020 (has links)
Concrete, as primary building material, is widely used in most construction project. For this reason, large amounts of concrete waste were generated from construction and demolition. One way to reuse concrete waste is to use it as backfill material for landfilling and road bases. While the demand for backfill material is decreasing as the basic infrastructure construction gradually completes. Another way to reuse concrete waste is to grind it and use it as aggregate in casting new concrete. However, the reuse as aggregate for casting concrete requires large amount of cement. It is unsustainable because the production of cement causes significant amounts of carbon dioxide emission. How to deal with the concrete waste in a sustainable way is presently an urgent issue. Powder compaction is a new approach to completely recycle concrete waste in an environmentally friendly way. This new method was studied in the Sakai lab of the Institute of Industrial Science, The University of Tokyo. The process consists of crushing and milling concrete waste into a fine powder, filling the powder into moulds and compacting it under high pressure. By this process concrete waste powder can be turned into a solid concrete with mechanical properties so that it has potentials to be used again as a building material. Data from previous studies show that the compacted concrete waste can reach strength for construction but the required compaction pressure is quite high. Wood flour can be added in compaction for improving tensile strength and reducing compaction pressure. Lignin is a wood substance that melts under high temperature, fills gaps and improves bonding between particles. Cellulose from the wood substance functions as fibres which improves tensile strength. Wood waste from production of timber building materials, furniture and other wooden products also forms a larger quantities. Recycling of concrete waste with wooden waste through heating compaction is a potentially sustainable method. This Master thesis presents research on the effect from different production conditions on the bending strength of recycled concrete waste with wood waste through heating compaction. The condition factors studied were compaction duration, compaction pressure, concrete proportion, mixture percentage, temperature and particle size of wood flour. To enhance the water resistance of this recycled product, different water resistance treatments were discussed theoretically. The independence of production condition factors was analysed using a statistic method. Results indicated that within a certain range, an increase in compaction duration, compaction pressure, the percentage of wood waste and temperature improves the bending strength of the recycled products. Using smaller particle size of wood flour cannot improve compaction but contribute to give higher bending strength. The mechanical properties of these recycled products suggest application as non-bearing building material, such as decoration tiles and bricks for partition walls. The application as a structural material is expected in the future as improvement treatments are discovered.
313

Biochar alleviates the negative impact of compaction on hydraulic conductivity in roadside stormwater control measures

Raabe, Matthew Theodore January 2022 (has links)
Compaction of urban soil where stormwater infrastructures are built reduces infiltration, vegetation growth, and stormwater treatment capacity. Biochar—a carbonaceous porous material produced by pyrolysis of organic waste – can be used as a soil amendment to improve the function of stormwater infrastructure in addition to the proven benefit of increased pollutant removal. However, the benefits depend on the biochar’s properties such as particle size distribution and concentration. Further, because biochar’s particle size distribution is altered by compaction, the hydraulic functions of compacted biochar amended soil is unknown. Herein, we examined the effect of biochar concentrations (0-6% w/w) and particle sizes (unsieved, sieved to < 2mm, and to < 0.5 mm) on water retention and saturated or unsaturated hydraulic conductivity of compacted stormwater media amended with biochar. Our results show the particle size of biochar plays a critical role in whether or not compaction is alleviated: while increasing concentration of unsieved biochar increased hydraulic conductivity up to 3% biochar, increasing concentration of fine biochar (< 2 mm) resulted in consistent decline in hydraulic conductivity under compaction. The results indicate that large biochar particles can effectively dissipate the compaction energy, while the fine biochar under compaction increased clogging by generating more fines that occupy the pores. Water retention improved regardless of the size distribution of added biochar, indicating that addition of biochar would reduce the irrigation requirement to maintain plant health in dry climate or water-stressed conditions. Overall, the results indicate that biochar addition can be effective in mitigating the negative impacts of compaction on stormwater infrastructures, depending on the proportion of coarse biochar. / Geology
314

The Effects of Coarse Aggregate Cleanliness on Asphalt Concrete Compactability and Moisture Susceptibility

Williams, Kevin Lamar 11 August 2012 (has links)
Twelve field projects were studied where fortyour locations were evaluated to assess the cause or causes of asphalt concrete that exhibits ‘tender zone’ characteristics and to investigate the tendency of these mixes to be susceptible to moisture damage. Data was collected during construction and samples were obtained to conduct laboratory tests. Field and laboratory data was used to develop multiple regression equations to predict final in place air voids and moisture susceptibility. The overall conclusion was that compactability appeared to be predicted in a reasonable manner while moisture susceptibility did not. The Methylene Blue test appears promising when used in conjunction with cold feed and/or mix moisture as a means of providing guidance for achieving higher in place density. The tensile strength ratio (TSR) test as performed in this research on laboratory compacted specimens was found to be questionable in terms of its ability to predict field moisture susceptibility.
315

Engineering Performance of Polymer Amended Soils

Welling, Gary E 01 August 2012 (has links) (PDF)
A laboratory test program was undertaken to evaluate a series of engineering properties over a range of soil types; amendment types and addition rates; and moisture contents to enhance understanding of the engineering significance of polymer amendment. Four soils were manufactured and tested with varying ranges of fines and plasticity. A proprietary elastic copolymer was tested at addition rates of 0.5% to 2.5% (dry weight basis). Cement was tested at addition rates of 1% to 4%. Lime was tested at an 8% addition rate. Water addition rates ranged from 4% dry of optimum to 4% wet of optimum. Engineering properties determined throughout the test program included dry unit weight / moisture content relationships through compaction tests; shear strength through unconfined compression strength tests and direct shear tests; durability through freeze-thaw and wet-dry durability tests; and stiffness through resilient modulus tests and through interpretation of the unconfined compression and direct shear test results. The addition of polymer altered the optimum moisture content of the soils. Change in optimum moisture content ranged from 0.51 to 1.27 times the control water demand. The dry unit weight of polymer amended specimens ranged from 0.97 to 1.01 times their respective control dry unit weight. The peak strength of polymer amended specimens ranged from 1.02 to 18.4 times the control strength. The peak wet-dry and freeze-thaw durability of polymer amended specimens ranged from 6.8 to 10.8 times the control durability. The addition of polymer increased the peak initial stiffness of specimens to approximately 3 times the control stiffness. However, the stiffness was reduced to 0.68 times the control stiffness with dynamic repeated loading through the resilient modulus test. The polymer addition rate required to achieve peak engineering performance ranged from 0.5% to 2.5%, based on soil type. Polymer modified the engineering properties of soil through physical bonding. The amount of polymer required to modify the engineering properties was directly related to specific surface and soil particle coating thickness. It was determined that polymer amendment had an optimal addition rate that resulted in the greatest increase in engineering parameters. The addition rate was optimum when polymer was applied at rates high enough to sufficiently coat all soil particle surfaces, but at rates low enough that it did not cause additional particle separation. Overall, polymer amendment of soil improved or maintained all tested engineering parameters, except the resilient modulus, of all soils. Polymer amended soils displayed a reduced performance compared to cement amended soils, and an improved performance compared to lime amended soils.
316

Effects Of The Soil Properties On The Maximum Dry Density Obtained Fro

Arvelo, Andres 01 January 2004 (has links)
In the construction of highways, airports, and other structures, the compaction of soils is needed to improve its strength. In 1933 Proctor developed a laboratory compaction test to determine the maximum dry density of compacted soils, which can be used for specifications of field compaction. The Compaction of soils is influenced by many factors, the most common are the moisture content, the soil type and the applied compaction energy. The objective of this research is the analysis of the maximum dry density values based on the soil classification and characterization. The method of choice in the determination of the maximum dry density from different soils was the Standard Proctor Test following the procedure for the standard Proctor test as is explained in ASTM Test Designation D-698. From this investigation, the maximum dry density of eight types of sands was obtained, the sands were classified by using the Unified Soil Classification System. The influence on the maximum dry density of the type of sands, type of fines, amount of fines and distribution of the grain size was determined, followed by a sensitivity analysis that measured the influence of these parameters on the obtained maximum dry density. The research revealed some correlations between the maximum dry density of soils with the type of fines, the fines content and the Uniformity Coefficient. These correlations were measured and some particular behavioral trends were encountered and analyzed. It was found that well-graded sands have higher maximum dry density than poorly graded when the soils have the same fines content, also it was encountered that plastic fines tend to increase the maximum dry density.
317

Soil compaction and the effect on infiltration in urban green environments : A study based on field measurements and HYDRUS 1D modelling

Novikova, Anastasia January 2023 (has links)
The consequences of recent flooding and extreme rain events have highlighted the importance of proper urban planning and preventative measures for storm water management. As cities become more urbanized the significance of permeable surfaces such as parks and other urban green spaces increases which infiltrate the water into the ground. Agricultural research has for many years emphasized the effect of compaction on soil parameters and how, not only the crop yield reduces but also how the infiltration decreases. This thesis aims to study how the infiltration rate, bulk density and soil resistance changes with compaction through field experiments where a vehicle is let to roll over an urban green area. The thesis will also simulate rainfall over five theoretical soils that can be found in urban environments exposed to compaction to determine what significance compaction has on surface runoff. The modelling software HYDRUS-1D will be used so simulate rain fall events on the different soils. The rain events simulated will be based on the five hyetographs that best represent Sweden’s rain events, based on historical data. A CDS rain will be simulated as well. They will be simulated for a 2, 10 and 100 year return period. A literature study will also be conducted to determine how relevant freeze-thaw cycles are to the soil parameters. It is since previously known that freeze-thaw cycles can improve aggregate stability, increase soil particle fragmentation which can lead to less soil penetration resistance and even partially return the soil conditions to those prior to compaction, but the process does not extend to layers beyond 40 cm. The field experiment results showed a clear decrease in infiltration rate with increasing number of vehicle passes. There was no clear correlation between bulk density and the number of vehicle passes. This result is attributed to the relatively light weight of the vehicle used as well as the heterogeneity of the soil. The cone penetration measurements showed an increasing resistance with increasing number of vehicle passes for only one of the three measured sites, with the most resistance being measured in a pathway on the green area. The insignificant results of one of the two other sites are attributed to wet weather conditions and unknown underlying material. The HYDRUS 1D simulations showed that a higher sand content mitigates the effects of soil compaction and leads to less runoff. The soil classified as sand (93% sand) had no runoff, the loamy sand (80% sand) had mild runoff. When comparing a sandy loam (60% sand) and a clay soil it is concluded that the sandy loam is more sensitive to soil compaction as more compaction leads to more runoff compared to the non-compacted scenario. The clay soil has little variation between the compaction scenarios but has generally more surface runoff in total. Soil texture therefor affects the surface runoff more than soil compaction. Most amount of runoff was generated by the two hyetographs which had a late peak intensity, most likely due to the soil already being saturated when the peak occurs. The runoff also increases with the return period of the rain event for both the hyetographs and the CDS rain.
318

PM processing of elemental and prealloyed 6061 aluminium alloy with and without common lubricants and sintering aids.

Youseffi, Mansour, Showaiter, N. January 2006 (has links)
No / A comparison has been made between compaction, sintering, microstructural and mechanical properties of the 6061 aluminium alloy prepared via premixed elemental (EL) and prealloyed (PA) powders (as received and degassed) with and without additions of sintering aids and various solid and/or liquid lubricants. Both EL and PA powders were cold pressed at different pressures, ranging from 250 to 770 MPa, and sintered under vacuum in the range 580-640°C for 30-120 min. and then under pure nitrogen atmosphere for comparison. Vacuum degassing of the PA powder provided better compressibility and thus higher green densities than those for the as received PA or the premixed EL powder compacts pressed at compaction pressures ¿340 MPa. Near full sintered densities of ~98%TD were obtained for both EL and PA 6061 Al alloys. Degassed PA Al with 0·6 wt-% paraffin wax (PW) or with only 0·12 wt-%Pb addition as sintering aid and no lubricant, and premixed EL with only 0·12 wt-%Pb addition and no lubricant gave the best optimum properties. It became apparent that additions of some solid lubricants such as lithium stearate (LS) and acrawax to both the premixed EL and PA powders provided reasonable green densities, but had deleterious effect on sintered densities and microstructures, particularly under vacuum sintering. Heating data curves during the sintering cycle, revealed formation of both transient and persistent liquid phases for the EL and mainly supersolidus liquid phase sintering (SLPS) mechanism for the PA. Tensile properties of the degassed, vacuum or nitrogen sintered PA Al alloy in T6 condition were higher than those of the equivalent alloy prepared by EL mixing with the former giving a tensile strength of 330 MPa and 6-8% elongation to failure, which are similar to those of the commercial (wrought) 6061 Al alloys.
319

Prediction Equations to Determine Induced Force on Reinforcing Elements Due to Laterally Loaded Piles Behind MSE Wall and Lateral Load Test on Dense Sand

Garcia Montesinos, Pedro David 17 December 2021 (has links)
Researchers performed 35 full-scale lateral load tests on piles driven within the reinforcement zone of a mechanically stabilized earth wall (MSE wall). Data defining the induced tensile force on the reinforcements during lateral pile loading was used to develop multi-linear regression equations to predict the induced tensile force. Equations were developed by previous researchers that did not consider the diameter of the pile, the fixed head condition, relative compaction, or cyclic loading. The purpose of this research was to include this tensile force data and develop prediction equations that considered these variables. Additionally, a full-scale lateral load test was performed for a 24-inch diameter pipe pile loaded against a 20-inch width square pile. The test piles were instrumented using load cells, string potentiometers, LVDTs, strain gauges and hybrid pressure sensors. The lateral load tests were used to evaluate the ability of finite difference (LPILE) and finite element (PLAXIS3D) models to compute results comparable to the measured results. The results of this analysis showed that the diameter of the pile is a statistically significant variable for the prediction of induced tensile force, and the induced tensile force is lower for piles with larger diameter. Fixed head conditions have no effect on the prediction of induced tensile force. Cyclic loading had minimal impact on the prediction of induced tensile force, but relative compaction did have an important statistical significance. Therefore, prediction equations for induced tensile force in welded wire were developed for relative compaction less than 95 percent and relative compaction greater or equal than 95 percent. A general prediction equation (Eq. 3-4) was developed for ribbed-strip reinforcements that included the effect of pile diameter and larger head loads. With 1058 data points, this equation has an R2 value of 0.72. A general prediction equation (Eq. 3-9) was also developed for welded-wire reinforcements that included data from cyclic and static loading, fixed and free head conditions, and relative compaction for 12-inch wide piles with a higher range of pile head loads. This equation based on 2070 data points has an R2 value of 0.72. The prediction equations developed based on all the available data are superior to equations developed based on the original set of field tests. The finite element models produced results with good agreement with pipe pile measurements while the finite difference model showed better agreement with the square pile measurements. However, for the denser backfills involved, back-calculated soil properties were much higher than would be predicted based on API correlations. The API equations are not well-calibrated for dense granular backfills.
320

The role of moisture profiling towards understanding pharmaceutical solid state functionality. Validation and the application of a moisture profiling analytical tool for investigation into the characterisation of and prediction of the effects of compaction and storage on different lactose physical forms

Seymour, Louise January 2015 (has links)
The majority of therapeutic pharmaceutical formulations are presented in the solid form. Moisture is able to play an important role in the functional performance of pharmaceutical solids. Moisture profiling is able to provide novel information with regards to the behaviour of moisture within materials using equilibrium relative humidity as a measurement. The hypothesis investigated explores the changes in equilibrium relative humidity of pharmaceutical material induced by physical, chemical or storage conditions, these are able to be monitored using the innovative moisture profiler system. The aims within this were to primarily validate the moisture profiler and secondly evaluate the effects of moisture on physical forms and with respect to effects of compaction, finally this was compared to conventional characterisation methods. Preliminary explorations were conducted in order to assess the validity of the moisture profiler, from this lactose was selected as a suitable pharmaceutical material for further work. Processing effects were then examined, firstly storage at elevated relative humidity of different forms of lactose were explored, and this was carried out with supplementary analysis. Secondly the effects of tabletting were explored, different compaction forces were investigated to observe if this had any notable effects on equilibrium relative humidity of the different lactose forms. Finally subsequent storage of the compacts were examined in order to explore if there were any changes in the equilibrium relative humidity. / EPSRC and Reckitt Benckiser

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