A Liquefaction Resistance of Sand-Fine Mixtures: Short Review with Current Research on Factors Influencing Liquefaction Resistance

Sand is well understood as susceptible material to liquefy under seismic condition. In many cases of liquefaction, the loss of property and damages occurred due to the earthquake phenomenon are caused by sandy soils. Thus, many laboratory experiments and field tests on soil liquefaction engineering have been mandatorily focusing on the liquefaction resistance of sand-fine mixtures. The interaction between sand and fines particles appears to be well studied subject. However, there are some contradictory findings on some factors influencing liquefaction resistance in sand-fine mixtures. Therefore, this paper aim to present results and current findings from previous researchers which focused on sand-fine mixtures using various type of sand to interpret liquefaction resistance and its behaviour. In addition, microstructure test needs to be conducted for verification and analysis of the results on grading and particle sizes characteristics. It has been identified that recent findings on the particle size distribution and grading characteristics of sand in sand-fine mixtures are still contradicting. It has also been found that there are no study using different types of sand to reconstitute tropical sand-fine mixtures; and limited study focused on the coefficient uniformity, CU and coefficient of curvature, CC on liquefaction resistance relationship

Performance of embankment on bamboo-geotextile composite reinforced soft clay

Road embankments and other constructions on deposits of natural soft clay are still a challenge in geotechnical engineering work. The used of various soil improvement methods to stabilise the soft clay need to be carried out in order to increase the bearing capacity and reduce the settlement. Most methods are costly while the time taken to complete the improvement works takes a long period. The Soft Soil Research Group of Universiti Teknologi Malaysia had proposed the combined used of bamboo as a green technology and a layer of low strength geotextile to become a reinforcement system called the “Bamboo-Geotextile Composite” (BGC). Full-scale embankments on BGC system reinforced soft clay (BGC embankment) together with an embankment on unreinforced soft clay (UR embankment) and also an embankment on high strength geotextile reinforced on soft clay (HSG embankment) had been constructed. Each embankment measured 10 m long, 16 m wide and about 3 m height. Semantan Bamboo of about 8 cm outer diameter with 48-94 MPa tensile strength and 43-49 MPa bending strength, and TS 40 Geotextile of 13.5 kN/m length tensile strength were selected as the materials for the system. In BGC system, the bamboo poles arranged in 1 m x 1 m square pattern were laid at the top of soft clay layer and the geotextile was then laid on top of bamboo. The objectives of this research are to determine the performance of BGC embankment and to develop a representative method of modelling the BGC embankment through the evaluation of field data using finite element (FE) model from PLAXIS 2D computer software. The embankments were monitored since the start of the construction until Day 418. Field monitoring data showed that the used of BGC system reduced more than 20% of immediate settlement and 57% of lateral movement during construction compared to UR embankment. The confinement of the soft clay in square pattern arrangement of bamboo increased the bamboo stiffness while the tensile resistance of horizontal ribs and compressive resistance of vertical ribs of bamboo prevented excessive settlement. The BGC system retained the surcharge load and distributed only small load to the underlain soft clay soil resulting in smaller consolidation settlement compared to UR and HSG embankments. The BGC system was best modelled as a geogrid element using PLAXIS 2D software. Although the drainage capability as well as the buoyancy effect of the BGC system could not be modelled, the settlement at the centre point of BGC embankment showed that the result from FE model differs only 1% from the field settlement at the end of construction while at Day 418, the model overestimated about 6%. For the lateral movement, the model predicted about 100% higher than the field value while the location of the maximum lateral movement was predicted to occur at a greater depth compared to the field performance. Hence, it can be deduced that the BGC embankment can be modelled using PLAXIS 2D software, in which the prediction for settlement can be better represented

Effects of particle size and grading characteristics on sand matrix soils under monotonic and cyclic loadings

Since 1964, liquefaction resistance of sand matrix soils or sand-fine mixtures has been extensively studied by researchers. These extensive studies were done/conducted following dramatic damages due to liquefaction caused by earthquakes in Niigata and Alaska. However, until the end of the 2010s and the latest major liquefaction occurrence in September 2018 at Palu, Indonesia, little research effort had been made to focus on the effects of particle shape and size, grading characteristics, particle arrangement and fines content of sand matrix soils. Although sand is the dominant material in sand matrix soils, there have not been enough efforts to elucidate the effects of particle size and grading characteristics of sand as the main factor in altering liquefaction resistance. Moreover, some results previously reported are still contradictory. This research aims to determine the effects of particle size and grading characteristics of sand on liquefaction resistance of sand matrix soils. To achieve the aim, three (3) objectives have been identified; (1) to evaluate the particle size, the grading characteristics and the physical properties of sand matrix soils at various compositions of sand and fines, (2) to establish the critical state line as the failure envelope of sand matrix soils from the results of monotonic undrained triaxial tests, and (3) to characterize the liquefaction susceptibility of sand matrix soils from the cyclic triaxial tests and validate through the centrifuge tests. The material used in the research was selected clean sand, which was sieved into three ranges of grain size that were coarse, medium and fine. Sand matrix soils were reconstituted by mixing these three-grain sizes of sand with low plasticity fines (kaolin) at 0% to 40% by weight. The results showed that the threshold fine content for coarse sand matrix soil and medium sand matrix soils were 30%, while for fine sand matrix soil, the percentage was 10%. From cyclic triaxial tests, it also indicated that the liquefaction resistance of sand matrix soils decreases with increases in fine content and showed a reverse trend after reaching threshold fine content. The threshold fines content (fth) for coarse sand matrix soils and medium sand matrix soils was 30%, whereas, for fine sand matrix soils, it was 10%. Threshold fines (fth) were observed to change the transition behaviour of sand dominates to fines dominates which occurred at different percentages of fines content depending on the grain size of sand. Less number of cycles was required to initiate soil liquefaction of sand matrix soils with a higher value of the coefficient of curvature and coefficient of uniformity. In general, the sand matrix soil has higher liquefaction resistance at larger sand particles. By using the centrifuge test, similar trends were observed as a result of the cyclic triaxial test. Some of the equations were generated to provide a new outcome for this research

Effects of sand sizes on engineering properties of tropical sand matrix soil

This paper presents an experimental study focusing on the effects of various sizes of sand on the engineering properties of tropical sand matrix soils, particularly the undrained shear strength. Static triaxial tests on reconstituted samples of sand with 0, 10, 20, 30, and 40% of low plasticity fines content by weight were carried out using GDS ELDYN® triaxial machine. The tests were performed on tropical specimens of three different sizes of sand (coarse, medium, and fine sand) which were mixed with kaolin as the fines content. Samples were tested at 15% relative density under two effective confining pressures of 100 kPa and 200 kPa, respectively. From the results of Consolidated Undrained Triaxial tests, the Critical State Line of the sand matrix soils with different sizes of sand had been developed. Based on the results from stress path diagram, the critical state parameters of sand matrix soils, represented by the critical stress ratio, M, are found to range from 1.41 to 1.35 for coarse, 1.38 to 1.29 for medium, and 1.30 to 1.25 for fine sand matrix soils. The maximum particle density was achieved at lower values of fines content for medium and fine sand matrix soils compared to coarse sand matrix soil. The sand size affects the maximum and minimum void ratio of sand matrix soils. At the same fines content, the void ratio of sand matrix soils increased as the sand size decreased

Liquefaction resistance of sand-fine mixtures: a review with current research on factors influencing liquefaction resistance

Sand is well understood as susceptible material to liquefy under seismic condition. In many cases o f liquefaction, the loss o f property and damages occurred due to the earthquake phenomenon are caused by sandy soils. The interaction between sand and fines particles appears to be well studied subject. However there are some contradictory findings on some factors influencing liquefaction resistance in sand-fine mixtures. Therefore, this paper aim to present results and current findings from previous researchers which focused on sand-fine mixtures using various type o f sand to interpret liquefaction resistance and its behaviour. It has been identified that recent findings on the particle size distribution and grading characteristics o f sand in sand-fine mixtures are still contradicting

Comparison of field performance between bamboo-geotextile composite embankment and high strength geotextile embankment

Trial embankment approximately 3 meters height, 10 meters of length, 16 meters width, and a slope of 1V: 2H was completed on soft clay site at RECESS, UTHM, Batu Pahat, Johor, Malaysia. Two embankments were respectively reinforced by a high strength geotextile (HSG) and the combination of bamboo and low strength geotextile or bamboo-geotextile composite (BGC) at the interface between embankment fill and foundation soil. Each embankment was installed with the same geotechnical instrumentation scheme for monitoring purposes. The purpose of this paper is to analyse the field performance for both embankments in terms of improving settlement embankment under the embankment. For this purpose, the settlement under the embankment, settlement at the surface of the embankment and the excess pore water pressure response were measured through geotechnical instrumentation for over 418 days. The results showed that the BGC system is more practical than HSG in terms of settlement and also in terms of cost, without compromising the quality of the embankment performance

Shear Strength Improvement of Soft Clay Mixed with Tanjung Bin Coal Ash

AbstractCoal is one of the world's most important sources of energy. The burning of coal produces coal ash that mostly consists of bottom ash (BA) and fly ash (FA). However, the utilization of coal ash in civil engineering construction applications has just received some attention within the last decade. This paper presents the strength improvement of soft clay mixed with coal ash. Kaolin was used to represent soft clay; mixed with 20%, 40% and 60% of BA and FA independently by weight. The optimum moisture content of kaolin was used in the mixing. Strength properties of mixtures had been carried out by conducting direct shear test and unconfined compression test. By adding FA to kaolin, the value of shear strength increased between 12 to 39 times the initial strength at different curing periods due to the pozzolanic reactions. From direct shear test of uncured mixtures, both kaolin – FA and kaolin – BA mixtures had similar strength at 40% - 60% FA or BA. Beyond this value as the percentage of FA increased the shear strength decreased but the increase in BA content increase the strength of mixture further

The grading effect of coarse sand on consolidated undrained strength behaviour of sand matrix soils

In geotechnical engineering field, the behaviour of soil does rely much on the shear strength for design purpose. Previously, findings show that the change of grained size in soil will change the structure (microstructure) and behaviour of the soil; consequently, affected the strength. To date, limited study focused on the effect of grading on the behaviour of sand fine mixtures. This study aims to investigate the effect of coarse sand on undrained strength behaviour of sand matrix soils in comparison with clean sand. A series of test on reconstituted sand matrix soils had been carried out by conducting consolidated undrained (CU) triaxial test using GDS ELDYN® triaxial machine. Coarse sand (retain within 2.0 mm to 0.6 mm) was mixed with 0%, 10 %, 20%, 30%, and 40% of fine particles (kaolin) independently by weight to prepare reconstituted samples. Triaxial samples of 50 mm diameter and 100 mm height were prepared using wet tamping technique (5% of moisture content) with targeted relative density at 15% (loose state). Each reconstituted sample was sheared at two effective confining pressures of 100 kPa and 200 kPa, respectively. Results show that the gradation contributed to the behaviour of the sand matrix soils. Increasing percentage of coarse sand in sand matrix soils exhibited higher effective friction angle. Similar trends were also observed on the angularity effect on undrained shear strength parameters