Journal of Civil Engineering Research and Practice

Performance of 4mm impact sprinklers at different spacing within acceptable pressure ranges (250-350 kPa)

G Soropa — 2011-09-10

Irrigation Engineers in Zimbabwe use the 12 m x 18 m spacing for the design of the sprayline, using 4 mm nozzle sprinklers. A study was conducted to determine performance and cost effectiveness of other spacings that can be used in sprinkler irrigation systems design. The main targeted spacings were a square layout of 15 m x 15 m and a rectangular layout of 15 m x 18 m. Water application uniformity and wetted diameter tests were done using the single line catch can layout method at 250 kPa, 300 kPa and 350 kPa using two locally manufactured (Toronto and Non Ferrous) and two imported (Rainbird and an Irriline) sprinklers. Highest coefficient of uniformity (CU) of 97 % and distribution uniformity (DU) of 95 % were obtained from a Rainbird sprinkler at 300 kPa. The lowest CU of 66 % and DU of 46 % were obtained from a Toronto sprinkler at 250 kPa. Highest wetted diameter (WD) of 32 m was obtained at 300 kPa from a Toronto sprinkler while lowest wetted diameter of 24 m was recorded at 250 kPa from a Toronto sprinkler. The results of CU, DU and wetted diameter showed that the 15 m x 15 m sprinkler spacing can be used in Zimbabwe under moderate wind conditions at 300 kPa, using preferably imported sprinklers for best application uniformity results.

Surface water quality in Kenya’s urban environment: Githurai Case Study

JW Kaluli — 2011-09-13

Safe, clean drinking water and sanitation facilities are key to economic development and public health in Kenya. Rapid urbanization and population growth mean worsening conditions for millions of Kenyans, especially the poorest. Sanitation is one of the greatest problems especially in the informal settlements where 60% of the people in the urban centers reside. In fact, 50% of all preventable illnesses in Kenya are related to water, sanitation and hygiene. This study was done to establish the level of indicator water quality parameters, and establish water borne disease prevalence in Githurai and adjacent communities. Water samples were collected from 6 points distributed uniformly along Kiu River in Githurai. Using standard methods, the samples were analyzed for Dissolved Oxygen (DO), BOD, TSS and TDS in the JKUAT environmental laboratory. A survey was also done in Githurai, Kahawa Sukari and Kahawa Wendani to establish the prevalence of water borne diseases. Data was collected from local medical clinics and Ruiru District Public Health Office. Randomly selected individuals were also interviewed to establish the frequency of visits to health facilities. The study revealed that dissolved oxygen in surface water was between 1.5 and 8.5 mg/L while biochemical oxygen demand (BOD) was between 200 and 400 mg/L. This was much higher than NEMA standards which demands that the BOD of any effluents to be discharged into the environment should be less than 30 mg/L. Total suspended solids (TSS) varied from 900 to 950 mg/L. NEMA allows domestic water not to have TSS of more than 30 mg/L. Total dissolved solids (TDS) were in the range of 3000 to 9000 mg/L compared to a maximum of 1200 mg/L which is allowed by NEMA. Surface water in Githurai is highly polluted and poses public health risks. Some 30-40% of all patients visiting hospitals in the study area suffered from diarrheal diseases and the average resident in Githurai was treated for water borne diseases once every three months. Therefore, an urgent intervention is required to clean up Kiu River and stop further contamination of the river.

Relevance Vector Machine for Prediction of Soil Properties

P Samui — 2011-09-10

One of the first, most important steps in geotechnical engineering is site characterization. The ultimate goal of site characterization is to predict the in-situ soil properties at any half-space point for a site based on limited number of tests and data. In the present study, relevance vector machine (RVM) has been used to develop three dimensional site characterization model of an alluvial site based on standard penetration test (SPT) results. In three dimensional analysis, the function N=N(X,Y,Z) where X, Y and Z are the coordinates of a point corresponds to SPT value(N), is to be approximated with which N value at any half space point in site can be determined. RVM provides an empirical Bayes treatment of function approximation by kernel basis expansion. It has also capability to estimate the prediction variance. The potential of RVM for prediction of N value is assessed in this study.

Assessment of Termite Re-worked Lateritic Soil as Highway Construction Material

AO Owolabi — 2011-09-14

The geotechnical properties of termite reworked lateritic soils and their suitability for road construction have been evaluated for selected sites in south western Nigeria. The evaluation reveals that termite reworked soils have higher plastic limits, specific gravities, Maximum Dry Densities (MDD) and California Bearing Ratios (CBR) than non-reworked soils, while their liquid limits, plasticity indices and Optimum Moisture Contents (OMC) are lower. The CBR (relative strength) values of the termite re-worked soils are higher at the queen region indicating fortification of the region against external ‘aggression’. The termite reworked lateritic soils have been adjudged suitable for sub-grade and sub-base of roads while they need to be stabilized before they can be used as base course material. They are in abundance in Nigeria and other African countries at an average volume of about 1.15 x 10⁶ m³ per square kilometre which is fairly large enough for application.

Assessment of Pumice Blocks in Comparison to Cement Sand Blocks and Burnt Blocks ‘The Case of Mbeya City - Tanzania’

HA Mboya — 2011-09-14

Modern buildings are standard and habitable structures that provide users with privacy, storage of properties, security and living area, amongst others. However, most people can’t afford in acquiring these modern structures due to lack of sufficient income. This paper assesses the properties of pumice materials on its particle sizes and the water absorption capacity. It also assesses the strengths of pumice blocks and wall units as compared with cement sand blocks and its walling units. The aim was to seek wider alternative choices of building materials. Samples of pumice material, and cement sand pumice blocks in different ratios have been prepared and tested in a laboratory. Results showed the tested pumice material to be classified as well-graded gravel. This material also had a maximum dry density of 663kg/m³ at optimum moisture content of 53%. The compressive strength of pumice block was found to be 4.8 N/mm² against 4.7 N/mm² cement sand block. Based on the characteristics of extraction and manufacturing processes, pumice materials are environmental friendly than burnt blocks that cause environmental degradation resulting from deforestation for firing woods. Pumice blocks are also of beneficial than cement sand blocks which are expensive and are liable to sand erosions when picked along the rivers. It is suggested that, pumice blocks are alternative to cement sand blocks and burnt blocks.

Root tensile strength of 3 typical plant species and their contribution to soil shear strength; a case study: Sasumua Backslope, Nyandarua District, Kenya

OS Nyambane — 2011-09-13

The effect of root reinforcement depends on the morphological characteristics of the root system, the tensile strength of individual roots, the soil-root cohesive strength, and the distribution of the root system in the soil. This research looks into Sasumua Backslope in Kenya, where a great deal of erosion is responsible for large soil losses. Shallow mass movements are evident throughout the slope. Root reinforcement effect of nine typical species was assessed, using Wu et al. (1979) model. The plant species comprised of shrubs (Atriplex halimus), grasses (Pennisetum clandistenum and Themeda triandra), and tree ferns (Asparagus species). Physical counting of roots per depth class was conducted to obtain root area ratio (RAR) values of the individual species. For each species, single root specimens were sampled and tested for tensile tests in the laboratory using the Hounsfield Tensometer apparatus. Maximum RAR values were located within 0.1 m for all the species, with maximum rooting depth of 0.7 m for fern tree. Shrubs species showed high RAR values between 0.1 – 0.3 m depth. Tensile force increases with diameter. Generally shrubs break at high tensile force (160 N maximum), followed by tree ferns (maximum 90 N) and lastly grass (maximum 75 N). Root tensile strength decreases with increasing root diameter, and follows a power law equation of the form . Generally, tensile strength can be well predicted by root diameter. The maximum root tensile strength values recorded was 39 N/mm² for grass. The results presented in this paper contribute to expanding the knowledge on root resistance behavior and on root density distribution within the soil. The studied location has allowed the implementation of soil–root reinforcement models initially used by Wu et al. (1979) and the evaluation of the vegetation contribution to soil stability.