Gabriele Chiaro

The 2015 Gorkha Nepal Earthquake: Insights from Earthquake Damage Survey

The 2015 Gorkha Nepal earthquake caused tremendous damage and loss. To gain valuable lessons from this tragic event, an earthquake damage investigation team was dispatched to Nepal from 1 May 2015 to 7 May 2015. A unique aspect of the earthquake damage investigation is that first-hand earthquake damage data were obtained 6 to 11 days after the mainshock. To gain deeper understanding of the observed earthquake damage in Nepal, the paper reviews the seismotectonic setting and regional seismicity in Nepal and analyzes available aftershock data and ground motion data. The earthquake damage observations indicate that the majority of the damaged buildings were stone/brick masonry structures with no seismic detailing, whereas the most of RC buildings were undamaged. This indicates that adequate structural design is the key to reduce the earthquake risk in Nepal. To share the gathered damage data widely, the collected damage data (geo-tagged photos and observation comments) are organized using Google Earth and the kmz file is made publicly available.

Determination of active earth pressure on rigid retaining wall considering arching effect in cohesive backfill soil

AbstractA new simplified method is proposed to compute the active earth pressure acting on the backface of a rigid retaining wall undergoing horizontal translation. The effect of soil arching for cohesive backfill soil and friction mobilized along the wall–soil interface was considered. Analytical expressions to determine the slip surface angle and the coefficient of active earth pressure were obtained using the limit-equilibrium approach. These expressions were used for the horizontal flat-element method to obtain theoretical formulas for the active earth pressure, active thrust, and its point of application. Additionally, an implicit solution was derived for the depth of the tension crack in the backfill. A parametric study was undertaken to assess the effects of cohesion, unit weight, friction angle, surcharge pressure, and wall–soil friction angle on the active earth pressure, as well as the effects of the friction angle of backfill soil and wall–soil friction angle on the slip surface angle. The resu...

Compaction of coal wash to optimise its utilisation as water-front reclamation fill

The coal mining industry in and around Wollongong, New South Wales, Australia, is responsible for producing an ever growing quantity of coal washery reject materials and other mine waste aggregates. Considerable effort is being undertaken to reuse, beneficially, these waste products in the immediate suburbs of Wollongong. In this paper, detailed laboratory investigations carried out on coal wash (i.e. coarse coal washery reject), produced at Dendrobium coal mine near Wollongong, are presented. Geotechnical tests were conducted to determine the particle size distribution, compaction characteristics, shear resistance and collapse potential. Compaction tests were performed under dry and submerged conditions to examine comprehensively the compactability and the strength properties of coal wash. The laboratory tests show that, if properly compacted, Dendrobium coal wash has a good potential as effective low-porosity fill for embankments and port reclamation.

A laboratory study on the shear behavior of mixtures of coal wash and steel furnace slag as potential structural fill

The accumulation of industrial waste materials (e.g., coal wash and steel furnace slag) has become a critical environmental problem in Australia in recent years. The possible re-use of these types of materials as structural fill for transport embankments and land reclamation is one of the preferred options from a waste management perspective. Consequently, an experimental testing program was undertaken using the triaxial apparatus to evaluate the shear behavior of compacted mixtures of coal wash (CW) and steel furnace slag (SFS). The effect of varying the confining pressure and the percentage of coal wash on the isotropic compression line, the stress-strain behavior, and particle degradation during drained shearing was evaluated. The percentage of coal wash was found to influence the shearing behavior of the CW-SFS mixtures. When the content of coal wash increased, the shear strength of the CW-SFS mixtures decreased and the axial strain corresponding to the peak stress ratio increased. Moreover, the incidence of particle breakage increased for those mixtures with a higher CW content due to the low particle strength of CW. This paper also provided a non-linear strength envelope and a corresponding empirical equation to capture the shear strength of CW-SFS mixtures.

Multiple-Liquefaction Behavior of Sand in Cyclic Simple Stacked-Ring Shear Tests

AbstractFollowing major earthquakes that occurred in New Zealand (2010–2011) and Japan (2011), soil multiple liquefaction, or reliquefaction, regained major attention in the field of geotechnical earthquake engineering. Not only can liquefaction occur multiple times at the same site, but the devastation caused by reliquefaction is often more severe than that triggered by the first liquefaction. In this study, to address this issue and provide new insights into reliquefaction mechanisms, a series of cyclic simple shear tests was conducted with the use of a newly developed stacked-ring shear apparatus. In the multiliquefaction tests, subsequent liquefaction stages were applied to a single Toyoura sand specimen sheared at different levels of maximum shear strain double amplitude (γDAmax), from 2% to 10%. Tests results showed that: (1) the increase in soil density during the postliquefaction reconsolidation stages had only a minor effect on sand resistance against multiple liquefaction; (2) the extent of γDAm...

A System to Measure Volume Change of Unsaturated Soils in Undrained Cyclic Triaxial Tests

It is common to employ a traditional double cell system, of which an open-ended inner cell is installed in an ordinary triaxial apparatus, to measure the volume change of unsaturated specimens. In such a system, the total apparent volumetric strain of the specimen (ev) is deduced from the water level change in the inner cell, monitored by a differential pressure transducer (DPT) considering, meanwhile, the top cap intrusion into the inner cell recorded by a vertical displacement transducer (VDT). Severe apparent volumetric strain, caused by the compliance of the double cell system (ev,SC), was observed during the undrained cyclic loading tests in a previous study. Test results on a steel-spring dummy specimen revealed that ev,SC was induced not only by such as the meniscus effect, but unexpectedly also by the asynchronous responses between the DPT and the VDT (i.e., the response of the DPT was delayed compared with that of the VDT). By doing some treatment ev,SC could be reduced to some extent, whereas the magnitude of ev,SC was still too high to be acceptable when the tested specimen approached the liquefied state. To radically solve these technical difficulties, a modified double cell system, named the linkage double cell system, was developed in this study. In this modified system, a linkage rod moving simultaneously with the loading shaft was introduced, through which the DPT could directly measure ev without considering the top cap or loading shaft intrusion. Test results for the steel-spring dummy specimen as well as for saturated and unsaturated soil specimens demonstrated that the linkage double cell system has major advantages in measuring accurately the volume change of the specimen during undrained cyclic triaxial loading tests compared with the traditional double cell system.

Field Investigation on Compaction and Strength Performance of Two Coal Wash-BOS Slag Mixtures

The effective reuse and recycling of industrial byproducts, namely coal wash (CW) and Basic Oxygen Steel slag (BOS), through large-scale geotechnical projects (e.g. land and port reclamation) is economically beneficial and environmentally sustainable. Nevertheless, due to the heterogeneity of these granular waste materials, the actual performance of compacted fill in the field can be significantly different from that observed in the laboratory. This paper reports the results of a compaction field trial carried out at Port Kembla Outer Harbor reclamation site (Wollongong, Australia) to evaluate the in-situ performance of two selected CW-BOS blends. Based on a number of field density tests, it was found that 4 passes of compaction were adequate for achieving a fill density > 90% standard Proctor compaction. A series of dynamic cone penetration tests (DCPTs) confirmed that compacted CW-BOS fills have a greater strength compared to compacted sandy fill, as the number of blows to penetrate 100 mm is greater than 20 for both materials. Furthermore, plate load tests were also performed and swelling was routinely monitored. The results are presented and discussed.

Characterization of compacted coal wash as structural fill material

In this paper, detailed laboratory investigations were conducted on coal wash produced at coal mine, Wollongong, New South Wales, Australia. Geotechnical tests were conducted to determine the particle size distribution, compaction characteristics, shear resistance and collapse potential. The compaction tests were conducted under dry and submerged condition to examine the compactability and the strength of the coal wash. The test shows that compacted coal wash has good potential as effective fill for embankments, and land reclamation. Although when coal wash is compacted under submerged condition, increased level of compaction has minimal effect. INTRODUCTION Recently, there has been a trend towards a more environmentally conscious society. As a result, waste minimization and waste recycling have been given a high priority in Australian industry. Mine waste including coal wash and furnace slag has both a monetary and an environmental benefit over conventional fills, if properly utilised in large construction projects (Indraratna et al. 1994; Kamon and Katsumi 1994; Lim and Chu 2006). Wollongong City, New South Wales located in the heart of coal mining and steel industry generates a mammoth volume of coal wash, blast furnace slag, mine waste aggregates and other granular by-products more than any other Australian city. Port Kembla is Wollongong’s commercial harbor that solely caters for the mining market. Due to the demand for port facilities, 45 hectares Outer Harbour adjacent to the existing port structures has been undergone major expansion via land reclamation to maximize the available land area in the port and to provide the maximum number of berths suitable for bulk cargoes and container handling to service regional importers and exporters. In Illawarra, large stockpiles of waste mine products such as coal wash and furnace slag have been produced 2.1 million tons per year. Due to the associated environmental concerns, the Port Kembla Port Corporation would consider the use of these locally abundant waste aggregates as the predominant reclamation fill, among the more conventional natural aggregates such as tunnel cuttings and used rail ballast from other parts of NSW. Based the existing geological information (Stroud et al. 1985), the volcanic sandstone bedrock can be found at the bottom of Outer Harbor area (RL -15 to -20m), while the thickness of the estuarine clay is relatively small. The type of reclamation fills used at Port Kembla would constitute a relatively important component of the total settlement, apart from the obvious implications on the load bearing capacity and long term settlement. If the port foundations are not properly stabilized, unacceptable settlement of fill material, sudden subsidence of granular media, large lateral displacements and differential movements can cause damage to the main structures, as well as to adjacent facilities (pipelines, retaining walls etc.). The improvement of the heterogeneous waste materials of coal wash in terms of geotechnical properties has been conducted in the past (Indraratna 1994; Sarsby 2000; Pusadkar and Ramaswamy, 2005). Compaction method has been found to be useful to improve the load-deformation behavior (stiffness) of underlying of soil layers, especially loose granular materials (Kettle, 1983, Koutsoftas and Keifer, 1990; Pan and Selby, 2002, Lee and Gu, 2004). It is generally acknowledged that granular waste fill can be effectively compacted in the field using dynamic compaction. Compaction rapidly decreases the soil porosity via mechanical energy thereby improving the engineering properties of soil including friction angle and elastic modulus. However, there is no past study conducted to evaluate the geotechnical properties of coal wash upon compaction in relation to shear strength and collapsibility potential above or below water table. According to Indraratna et al. (1994) the collapse mechanism is controlled by three factors; (a) potentially unstable structure, such as flocculent type associated with soils compacted dry of optimum; (2) a high applied pressure which further increases the instability; and (3) a high suction which provides the structure with only temporary strength which dissipates on wetting. Evaluating the compaction characteristics of coal wash remain to be a most fundamental and essential component of this study. COAL WASH CLASSIFICATION The coal wash is a waste by-product of coal mining operations in the Illawarra. It is produced by the coal washery process used to refine raw, run-of-mine coal material. The properties of coal wash are not uniform because the mineral components are likely to vary from one place to another. Figure 1 shows the coal wash sample used in the testing program. The coal wash sample is a well graded, black, heterogeneous soil with varying constituent elements including coal. These constituents depend on the nature of the surrounding geology and mining processes used. This consists of any rock or soil strata local to the coal seam being mined. Table The specific gravity of coal wash sample is 2.04. The plastic and liquid limits are 17.7% and 27.2%, respectively. The sieve analysis was conducted according to ASTM standards. The grain size distribution of the coal wash is shown in Fig. 2. Based on the Unified Soil Classification System, the coal wash can be categorized as well graded sand (SW) with a uniformity coefficient of 10-12. The D50 size is in the order of 2.5mm, and the largest 20% of the particle fraction in the range of 6-10 mm. Figure 1. Coal wash sample 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 0.010 0.100 1.000 10.000 100.000 % F in er (% ) Particle Size (mm) Series1 Series2

Effect of a cement-lignin agent on the shear behavior of Shanghai dredged marine soils

ABSTRACT With the rapid urbanization in Shanghai, China, suitable fill materials have been reported to be in great shortage in recent years. A prospective solution to these issues is to convert the huge amount of existing dredged marine soils to construction materials via solidification. However, there have been no studies on the shear behavior of solidified dredged materials from Shanghai region so far, while it has been reported by various researchers that the available data obtained from certain types of clay cannot be confidently and readily applied to other types of soils. To address this challenging issue, in this article, samples of Shanghai marine dredged soils were retrieved from the world’s largest reclamation project in Shanghai Lin-gang New City. A series of laboratory tests have been conducted to investigate the shear behavior of Shanghai dredged marine soils solidified using a new composite curing agent made of cement and lignin. The test results and the effect of this cement–lignin agent on the shear behavior of Shanghai marine soils, including the stress–strain behavior, shear strength properties, and failure characteristics are presented and discussed, which can provide valuable reference for the use of dredged soils as construction materials in the Shanghai region.

An Elasto-plastic Model for Liquefiable Sands Subjected to Torsional Shear Loadings

This paper presents a modeling procedure for simulating the monotonic undrained torsional shear behavior of sands, including stress-strain relationship, and excess pore water pressure generation, while considering the void ratio and stress level dependence of stress-strain-dilatancy behavior of sand. A unique set of soil parameters is required by the model to satisfactorily predict the undrained behavior of loose and dense Toyoura sand over a wide range of initial void ratios and confining pressures, as proven by simulating experimental data produced by the authors and found in the literature.