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Abstract

Geophysical and geotechnical techniques were used to investigate the sub-surface information of a proposed site for a hostel construction at Federal University of Agriculture, Abeokuta. Ten vertical electrical sounding (VES) stations were adopted. Typical sounding curves obtained include the HA, KH, AKH and KQH types, of which the AKH-type consists of 40% of the survey points, and a maximum of five geo-electric sub-surface layers were delineated. Laboratory analyses were performed to investigate particle size distribution, Atterberg limit, compaction limit, California bearing ratio (CBR) and specific gravity. The CBR revealed that all soil samples, except L4, are mechanically stable and have high load-bearing capacity. The Atterberg limit test and the geo-electric section showed that the second layer of VES 4 is composed of sandy clay with high plastic index and low liquid limit, which may pose a threat to the foundation of any engineering structure. VES locations 5, 6 and 8 were identified as high groundwater potential zones suitable for optimum groundwater abstraction. The study area is suitable for both shallow and deep foundations, however VES 4 and VES 5 require reinforcement.

Abstract

Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and phosphogypsum varied from 0 to 10 %. The results reveal that the dry unit weight and optimum moisture content of bentonite + 8 % lime increased with the addition of 8 % phosphogypsum. The percentage of swell increased and the free swell index decreased with the addition of 8 % phosphogypsum to the bentonite + 8 % lime mix. The unconfined compressive strength of the bentonite + 8 % lime increased with the addition of 8 % phosphogypsum as well as an increase in the curing period up to 14 days. The liquid limit and plastic limit of the bentonite + 8 % lime increased, whereas the plasticity index remained constant with the addition of 8 % phosphogypsum. The California bearing ratio, modulus of subgrade reaction, and secant modulus increased for the bentonite stabilized with lime and phosphogypsum. The coefficient of the consolidation of the bentonite increased with the addition of 8 % lime and no change with the addition of 8 % phosphogypsum.

1 Introduction Soil and mixture of aggregates compaction is one of the methods of enhancing ground and road surface layers. The compaction results in an increase of the bearing capacity of particular layers of road surfaces in conditions similar to optimum moisture content and its consequence is a guarantee of proper work of construction without distortions/deformations complying requirements of particular road traffic rules. A basic test to evaluate soil or substructure bearing is CBR ratio test (California Bearing Ratio) [ 16 , 23 ]. Value of this bearing is a

Infrastructure PROJECTS, 27-28 Feb 2017, Thiruvananthapuram. IS:2720 (1992) (Part 16) California Bearing Ratio Test, Bureau of Indian Standards, New Delhi, India. IRC: SP-20 (2002) Rural Roads Manual, Indian Roads Congress, New Delhi, India. Madhavi Latha, G. (2013) Performance Evaluation of Geosynthetic Reinforced Unpaved Roads, Centre for infrastructure, Sustainable Transport and Urban Planning (CiSTUP), Indian Institute of Science, Bangalore, India. Sanjay, M., Sindhi, P.R., Vinay, C., Ravindra , N. and Vinay, A. (2016) Crushed rock sand:An economical and ecological

Abstract

The research investigated the effects of palm kernel shell ash (PKSA) on lime-stabilized lateritic soil. Preliminary tests were performed on three soil samples, i.e., L1, L2 and L3 for identification; the results showed that L1 was A-7-6, L2 was A-7-6, and L3 was A-7-6. The optimum amount of lime for each of the soil samples was achieved. The optimum amount for L1 was 10%, for L2, 8% and for L3, 10%; at these values they recorded the lowest plasticity indexes. The further addition of PKSA was performed by varying the amount of PKSA and lime added to each of the soil samples. The addition of 4% PKSA+ 6% lime, the addition of 4% PKSA + 4% lime, and the addition of 4% PKSA + 6% lime increased the California Bearing Ratio (CBR) to the highest values for L1, L2 and L3 from 8.20%. It was concluded that PKSA can be a suitable complement for lime stabilization in lateritic soil.

Abstract

This study assesses stabilizing lateritic soil using Terrasil solution. Preliminary tests were carried out on six natural soil samples from three borrow pit locations-two soil samples from a particular borrow pit location, for the purpose of identification and classification. Soil samples 1 and 2 from borrow pit 3 were found to be poor, hence, needed stabilization. While the other four samples from borrow pits 1 and 2 were found to be good enough. Engineering property tests such as California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS) and Compaction tests were performed on both the natural soil samples and the stabilized lateritic soil samples which were stabilized by adding terrasil solution in percentages ranging from 0% to 16% at 2% interval. The results showed that the addition of terrasil solution enhanced the strength of the two soil samples from borrow pit 3. For soil sample 1, the unsoaked CBR values increased from 8.4% at 0% to optimum value of 30.3% at 12% terrasil solution, while for soil sample 2, the unsoaked CBR values increased from 6.2% to optimum value of 32.0% at 12% terrasil solution. It was therefore concluded that the terrasil solution serves as a cheap and effective stabilizing agent for poor soil.

. Geotechnique, 40(3), pp. 405-430. Alonso, E. E., Vaunat, J., & Gens, A. (1999). Modelling the mechanical behavior of expansive clays. Engineering Geology, 54 , 173-183. AS 1289.5.1.1. (2017). Methods of testing soils for engineering purposes—Soil compaction and density tests—Determination of the dry density/moisture content relation of a soil using standard compactive effort. Australian Standards, Sydney, Australia. AS 1289.6.1.1. (2014). Methods of testing soils for engineering purposes—Soil strength and consolidation tests—Determination of the California Bearing Ratio of

methods for laboratory reference density and water content. Proctor compaction, Slovak Office of Standards. STN EN 13286-47 (2012) Unbound and hydraulically bound mixtures. Part 47: Test method for the determination of California bearing ratio, immediate bearing index and linear swelling, Slovak Office of Standards. KLK 1/2012 (2012) Catalogue sheets of aggregates , Ministry of Transport, Construction and Regional Development of the Slovak Republic. TKP 5 (2014) Technical qualitative requirements, Base layers, Ministry of Transport, Construction and Regional

geotechnical properties of expansive clay soils such as California Bearing Ratio (CBR) and shear strength is highly recommended. Conflict of interest : The authors declare that there are no conflicts of interest associated with this paper. References [1] Mallela, J., Harold Von Quintus, P., Smith, K.L. (2004). Consideration of Lime-Stabilized Layers in Mechanistic-Empirical Pavement Design The National Lime Association, Arlington, VA, USA. Mallela J. Harold Von Quintus P. Smith K.L. 2004 Consideration of Lime-Stabilized Layers in Mechanistic-Empirical Pavement Design The