Abstract – December 2023 Issue

Engineering Characterization of Bedrock and Design of Rock-Socketed Bored Pile in Eastern Thailand

S. Yimsiri, S. Eua-apiwatch, and W. Ratananikom

ABSTRACT: This study aims at evaluating and improving design methods of rock-socketed bored piles in Eastern Thailand.  The properties of the bedrock at Sriracha district in the Eastern of Thailand are investigated, including physical, index, and engineering properties.  Empirical correlations among the obtained index and engineering properties of the bedrock are derived and proposed, which are quIs(50), quHR, and stHR, although the strength of these relationships are quite low.  The empirical equations for a rock-socketed bored pile design for the studied area are proposed by verifying them with the dynamic pile load test results.  The obtained equations of side and tip resistances are compared with those proposed by various researchers and some comments are also made.

KEYWORDS: Rock-socketed bored pile, Pile capacity, Rock property, Empirical equation, and Dynamic pile load test.

Neutralization of Phosphogypsum for Use in Base Lining System of Phosphogypsum Dumping Yards

N. V. Satyanarayana Reddy, and K. Tulasi

ABSTRACT: Phosphogypsum is generated as a by-product during the manufacturing of phosphoric acid by wet process. Annually, the worldwide projected value of phosphogypsum generation is 100-280 metric tons. Due to its acidic nature, radioactivity, high fluorine content, presence of trace elements and huge volume, direct dumping of phosphogypsum on the ground results in subsoil and groundwater contamination. Hence, it is essential to dump phosphogypsum properly in engineered landfills. To overcome these issues in India, the Central Pollution Control Board (CPCB) has suggested a composite liner system for the safe disposal of phosphogypsum on the ground. The lower part of the suggested liner system comprises of placement of HDPE geomembrane over a layer of compacted clay or compacted amended soil layer or a mixture of native soil with bentonite and in the upper part of the composite liner system, a layer of mechanically compacted and neutralized phosphogypsum is placed above the drainage layer. Hence, the present work is intended to neutralize phosphogypsum with lime, fly ash, and pond ash and to assess the suitability of neutralized phosphogypsum for use in the upper part of the composite liner system of phosphogypsum ponds. The study indicated effective neutralization of phosphogypsum with 1.6% lime and 50% fly ash.

KEYWORDS: Phosphogypsum, Composite Liner System, Neutralization, Lime, Fly ash, and Pond ash.

Stability Analysis of Jointed Rock Slope with Strength Reduction Method Based on a 3DEC Simulation

Fei Guo, Gang Zeng, and Ling Yue

ABSTRACT: To investigate the application of strength reduction method in the stability analysis of rock slope, a rock slope model with two sets of joints is established in the 3D discrete element code (3DEC) software. Different strength reduction algorithms are used to solve the slope safety factor and the slope failure form in critical condition. Results indicate that it is more reasonable to adopt the coordinated reduction method for the unjointed slope model. However, for the slope model with two groups of joints, the slope is stable when only the rock block parameters are reduced, resulting in a small amount of toppling deformation. The numerical results of only reducing the structural plane parameters are consistent with those of reducing all parameters. The safety factor of the rock slope model with two groups of joints is 1.30, and tensile shear failure occurs along the structural plane. Taking the convergence of the displacement of the monitoring points on the slope surface as the criterion of slope instability, the reduction factor when the slope is in a critical state can be obtained from the displacement curve. The reduction of structural plane parameters should be mainly considered when the discrete element strength reduction method is used to calculate the safety factor of rock slope.

KEYWORDS: Strength reduction method, Jointed rock slope, Safety factor, Numerical simulation, and Discrete element method.

Mitigation of Adverse Effects of Sulfates in Cement Treated Marine Clay Subgrades

Merin Kuriakose, Benny Mathews Abraham, and Anitha G. Pillai

ABSTRACT: Marine clays are normally characterized by high compressibility and low shear strength, which contribute to many geotechnical problems and, at times, necessitate the need to adopt stabilization with calcium-based stabilizers. However, calcium-based stabilization, when adopted on clays rich with sulfates, causes sulfate heaving, which impacts the strength of the soil. As a result of this heaving, severe damage has occurred to transportation infrastructure such as highways, runways, tunnels, canals, etc. Numerous pavement failures attributed to sulfate-induced heave in cement-treated sulfate-bearing clay subgrades have been documented by researchers worldwide. In this study, an attempt was made to prevent the sulfate attack in cement-treated clay by introducing barium hydroxide and sulphate resisting cement. Unconfined compressive strength, CBR, liquid limit and free swell index tests were conducted on treated clay samples to determine the effect of sulfates in cement-treated sulfate-bearing clays for prolonged curing periods. On the basis of the results obtained, the incorporation of barium hydroxide produced a high CBR value of 70% and a strength gain of 551 kPa in treated clay samples, indicating the effectiveness of barium hydroxide in mitigating the adverse effects of high sulfate content in soil. It was also determined that the sulphate-resistant cement was sufficient to lessen the impact of 0.5% sulfate content in soil, but it was unable to mitigate the impacts of 4% sulfate, resulting in a significant reduction in strength of 34%.

KEYWORDS: Sulfate, Expansive soils, Marine clay, OPC, SRC, and Barium Hydroxide.

Unconfined Compressive Strength of Weakly Cemented Compacted Sand under Different Loads

Messaouda Redjem, Mustapha Hidjeb, Ihcene Lamri, and Khaled Boudjellal

ABSTRACT: The exploitation of dune sand for public works, notably in Skikda’s northeastern region in Algeria, is a topic of significant interest, given the region’s rich sand resources, with the aim of optimizing its effective utilization.This context led to an experimental study focusing on the behavior of cement-stabilized dune sand under static and cyclic loads. The study included various tests: Compaction, California Bearing Ratio (CBR), and Unconfined Compression Strength (UCS). The normal Proctor compaction and CBR tests were carried out on specimens of sand with cement contents of 0, 2, 4 and 6%. The unconfined compression tests were carried out at rates of loading 0.05 mm/min and 0.1 mm/min. Cyclic displacement-controlled unconfined compression tests were performed at a frequency of 0.002 Hz. This tests were conducted on samples cured for 7 and 28 days with a cement content of 0, 2, and 4 %. The research aimed to understand how cement content, loading rate, curing time, frequency, and the number of cycles affect the mechanical properties of the soil. Results under static loading revealed that the low rate of loading, the increase in curing period, and the increase in cement content increased the UCS. This increase was notably evident in a sample with 4% cement content, aged 28 days, and loaded at 0.05 mm/min, showing a UCS approximately 29% higher than a similar sample tested at 0.1 mm/min. It has also been observed that at low loading rate, a denser soil-cement composite is obtained, leading to a more dilatant behavior, resulting in an increase in the modulus of elasticity. Under cyclic loading have shown that with a low frequency and increased cement content, along with an increase in the number of cycles and curing time, both the strength and elastic modulus increase. Conclusively, the results suggest that stabilizing dune sand with cement, considering factors such as low loading rates, curing time, low frequency, and increased cycles, significantly enhances the material’s resistance under various loading conditions.

KEYWORDS: Sand, Cement, UCS, Modulus of elasticity, and Different loads.

Ground Improvement in Loose Sandy Soils through Dynamic Replacement

Nabil F. Ismael, Dalya Ismael, and Najlaa Al Otaibi

ABSTRACT: The challenge of maintaining the stability and longevity of structures in areas with high fines content soils necessitates effective ground improvement strategies. One such strategy, dynamic replacement, has been successfully implemented in the developing city site of Jaber Al Ahmed, around 25 km west of Kuwait City. The site’s soil profile features extensive sand deposits varying from very loose to medium, silty, and clayey, reaching a depth of roughly 10 m. Areas characterized by fines content exceeding 30% were earmarked for improvement. The dynamic replacement technique involves the creation of a crater by dropping a heavy weight, subsequently filled with imported granular material, forming a stiff granular column within the soil. This reduces soil compressibility and settlement significantly while increasing bearing capacity under applied foundation loads. Through an extensive laboratory and field-testing program encompassing an area of 36,000 m2, soil conditions were assessed using boring and sampling, Standard Penetration Tests, Cone Penetration Tests, and Pressuremeter Tests, both before and after the dynamic replacement. The results were marked improvements in ground conditions, satisfying the specified acceptance criteria with a minimum allowable soil pressure of 300 kN/m2 for the foundation design of the housing project’s structures. This study highlights the impact of dynamic replacement as a ground improvement strategy in terrains rich in fines, establishing a paradigm shift towards resilient, sustainable, and economically viable construction methodologies, with a significant potential to revolutionize infrastructure development in similar geological settings worldwide.

KEYWORDS: Loose Silty Sands, Ground Improvement, and Dynamic Replacement.

Numerical Study of a Quay Wall Anchored by an Anchor Plate Backfilled with a Mixture of Sand and Recycled Waste

By F. Z. Benamara, C. Kechkar, M. Feligha, M. Bencheikh, and L. Louetri

ABSTRACT: Ideal backfill materials are granular stone, gravel, clean sand with a low percentage of fines. Such material is durable, strong and allows free circulation of water. Due to the depletion of available natural materials, recycled waste will be mixed with sand to form a reinforced fill which can be applied as contiguous fill for retaining walls, mechanically stabilized earth walls and bridge abutments. In this work, a numerical study is carried out by finite elements using PLAXIS 2D software on the Galay quay wall anchored by an anchor plate (sheet pile). In order to study the effect of adding recycled materials on the behavior of the anchored quay wall, three types of backfill based on sand and recycled materials (tire chips, fiberglass, plastic fiber) at different percentages were used as backfill behind the quay wall. The numerical results confirmed that recycled waste is an effective agent for improving the behavior of sandy soils used as backfill behind the anchored quay walls by reducing horizontal displacements and constraints and vertical overall (quay wall – backfill – anchor).

KEYWORDS: Backfill, Recycled materials, Anchor plates, Quay wall, and PLAXIS 2D.