Planning and Implementation of a Mega Geotechnical Engineering Project in Singapore

Implementation of mega geotechnical engineering projects requires a systematic approach and detailed planning. A mega land reclamation and ground improvement project which consists of various components of geotechnical engineering applications was planned and implemented in the Republic of Singapore from 1990 till 2005, a total period of one and a half decades. Due to the extensive ground improvement required to treat the underlying highly compressible soil, with the presence of highly variable ground profile and ground conditions due to the natural geological process, a detailed ground investigation was necessary. This was furthermore necessary due to the importance of various critical infrastructure planned for future usage in the land reclamation site. Extensive ground investigation was planned based on input from desk study and reconnaissance survey carried out using geophysical method under foreshore conditions. Progressive ground investigation included ground investigation carried out in foreshore area prior to land reclamation, on land prior to ground improvement, during and after ground improvement to assess the degree of improvement. The ground investigation involved large numbers of in-situ tests using numerous methods and collections and testing of undisturbed soil sample for further laboratory testing to drive necessary geotechnical parameters for design purpose or decision making for acceptance of ground improvement works. Due to the nature and speed of the project on-site geotechnical and geotextile laboratories were set up for characterization and quality control. In addition to the improvement of underlying soils, hydraulically filled granular soils were required to be densified by application of deep compaction methods to minimize future immediate settlement and to increase resistance to liquefaction. A large quantity of geotechnical instrumentation were installed and monitored for construction control as well as performance monitoring of ground improvement works. This paper describes the procedure and process of implementation of geotechnical works in the mega Changi East Land Reclamation and Ground Improvement project in Singapore

Stabilization of a 30 m High Riverbank in Canada with Nails, Plates and Roots

The natural river processes along a 30 m high riverbank of one of the largest tributaries to Lake Superior cause periodic landslides. After arresting toe erosion, local authorities needed to protect the infrastructure at the crest from further damage as the slope continued to flatten towards its long-term angle of repose. A long-term hazard management strategy was applied using the cautionary zone approach (CZA). Design criteria included a target safety factor, no construction impacts, no maintenance and a 75-year design life. The solution drew from 3 technologies: soil nails, laterally loaded piles and biotechnical stabilization. Steel nails, 35 mm diameter, were designed in bending perpendicular to slip surfaces and installed on a 1 to 1.5 m grid. Lightweight equipment working on the slope installed the 4 to 12 m long nails very rapidly without drilling or grouting. For shallow flow slides around a rigid nail, plate heads were added. A facing of roots controlled soil movements between nails and provided a natural look with the system completely out of sight. Three years of performance monitoring data are presented, and confirm a successful case history. This paper describes an innovative approach used to stabilize a landslide prone area in an urban environment

Laboratory testing of soils, rocks and aggregates

Testing rocks and aggregates are rarely covered in soil testing books and there are no separate books on rock or aggregate testing. Laboratory Testing of Soils, Rocks and Aggregates includes laboratory testing methods for most tests for soils as well as rocks and aggregates, which are becoming increasingly common in professional practice and university teaching. Part A gives a general overview of laboratory measurements, equipment, units, safety and standards. Part B covers soil tests from grain size distribution to consolidation, triaxial and direct shear tests. Part C covers rock tests, which includes the indirect tensile strength test and point load test. Part D covers the common tests carried out routinely on aggregates, which includes the aggregate impact value test and Los Angeles abrasion test. Each test consists of the following descriptive parts: Objective, Standards, Introduction, Procedure, and Cost. References are made to ASTM International (ASTM), Australian (AS), British (BS) and International Society of Rock Mechanics (ISRM) standards and any differences are noted

Municipal solid waste management under Covid-19: Challenges and recommendations

Covid-19 is proving to be an unprecedented disaster for human health, social contacts and the economy worldwide. It is evident that SARS-CoV-2 may spread through municipal solid waste (MSW), if collected, bagged, handled, transported or disposed of inappropriately. Under the stress placed by the current pandemic on the sanitary performance across all MSW management (MSWM) chains, this industry needs to re-examine its infrastructure resilience with respect to all processes, from waste identification, classification, collection, separation, storage, transportation, recycling, treatment and disposal. The current paper provides an overview of the severe challenges placed by Covid-19 onto MSW systems, highlighting the essential role of waste management in public health protection during the ongoing pandemic. It also discusses the measures issued by various international organisations and countries for the protection of MSWM employees (MSWEs), identifying gaps, especially for developing countries, where personal protection equipment and clear guidelines to MSWEs may not have been provided, and the general public may not be well informed. In countries with high recycling rates of MSW, the need to protect MSWEs' health has affected the supply stream of the recycling industry. The article concludes with recommendations for the MSW industry operating under public health crisis conditions

Deformation of ultra-soft soil

This study investigated the deformation behavior of ultra-soft soil upon additional load application. Various types of labortary compression tests were conducted, such as tests using small and large-scale consolidometers, hydraulic Rowe cells under different drainage conditions, Constant Rate of Loading and Constant Rate of Strain tests.Doctor of Philosophy (CEE

Planning and implementation of a mega geotechnical engineering project in Singapore

Implementation of mega geotechnical engineering projects requires a systematic approach and detailed planning. A mega land reclamation and ground improvement project which consists of various components of geotechnical engineering applications was planned and implemented in the Republic of Singapore from 1990 till 2005, a total period of one and a half decades. Due to the extensive ground improvement required to treat the underlying highly compressible soil, with the presence of highly variable ground profile and ground conditions due to the natural geological process, a detailed ground investigation was necessary. This was furthermore necessary due to the importance of various critical infrastructure planned for future usage in the land reclamation site. Extensive ground investigation was planned based on input from desk study and reconnaissance survey carried out using geophysical method under foreshore conditions. Progressive ground investigation included ground investigation carried out in foreshore area prior to land reclamation, on land prior to ground improvement, during and after ground improvement to assess the degree of improvement. The ground investigation involved large numbers of in-situ tests using numerous methods and collections and testing of undisturbed soil sample for further laboratory testing to drive necessary geotechnical parameters for design purpose or decision making for acceptance of ground improvement works. Due to the nature and speed of the project on-site geotechnical and geotextile laboratories were set up for characterization and quality control. In addition to the improvement of underlying soils, hydraulically filled granular soils were required to be densified by application of deep compaction methods to minimize future immediate settlement and to increase resistance to liquefaction. A large quantity of geotechnical instrumentation were installed and monitored for construction control as well as performance monitoring of ground improvement works. This paper describes the procedure and process of implementation of geotechnical works in the mega Changi East Land Reclamation and Ground Improvement project in Singapore

Characteristics of Singapore marine clay at Changi

Singapore marine clay at Changi is a quartenary deposit that lies within valleys cut in the Old Alluvium. It is locally known as Kallang formation. The pre-reclamation site characterization and laboratory testing was carried out by conducting marine sampling boreholes, in situ dissipation tests and field vane test. In situ dissipation tests were conducted with the piezocone, flat dilatometer, self-boring pressuremeter and BAT permeameter. The purpose of the site characterization was to determine the consolidation characteristics, strength characteristics, stratigraphy, and mineralogy of Singapore marine clay. The consolidation properties of marine clay are required prior to land reclamation activities in order to predict the magnitude and rates of settlement with the expected fill load and future service load as well as for the design of soil improvement works. The shear strength properties are required for slope stability analyses during reclamation and for the stability analyses of shore protection works. Clay mineralogy tests and photographic identification of the marine clay was carried out to determine the mineralogical properties and to visually record the marine clay colour and texture

Factors affecting consolidation related prediction of Singapore marine clay by observational methods

The use of prefabricated vertical drains with preloading option is the most widely-used ground improvement method for the improvement of marine clays in land reclamation projects. The assessment of the degree of consolidation of the marine clay is of paramount importance prior to the removal of preload in such ground improvement projects. This analysis can be carried out by means of observational methods with the use of field settlement plates and piezometer monitoring. Field settlement monitoring data can be used to ascertain the settlement of the reclaimed fill from the time of initial installation. The field settlement data can be analysed by the Asaoka method to predict the ultimate settlement of the reclaimed land under the surcharge fill. Back-analysis of the field settlement data will enable the coefficient of consolidation due to horizontal flow to be closely estimated. Piezometer monitoring data can be analysed to obtain the degree of consolidation of the improved marine clay. Back-analysis of the piezometer data will also enable the coefficient of consolidation due to horizontal flow to be estimated. The aim of this paper is to highlight the significance and impact of the various factors that affect prediction by the Asaoka and piezometer assessment methods. The authors findings of the Asaoka method reveal that the magnitude of ultimate settlement decreases and the degree of consolidation subsequently increases as a longer period of assessment is used in the prediction. The degree of consolidation predicted by the piezometers is found to be in good agreement with the Asaoka method for the early period of assessment. However as the assessment period increases, the piezometer indicates lower degree of consolidation as compared to field settlement predictions

Finite element modelling of marine clay deformation under reclamation fills

The ongoing Changi East Reclamation Project in Singapore consists of land reclamation and ground improvement of the foreshore for the future expansion of Changi International Airport. The deformation behaviour of marine clay under reclamation fills and surcharge was modelled by the finite element method (FEM) with Plaxis numerical modelling software. The analyses included modelling the consolidation behaviour of marine clay under reclamation fills with and without prefabricated vertical drains. Marine clay with vertical drains was modelled by both the axisymmetric unit cell and full-scale analysis methods. Marine clay that was not treated with prefabricated vertical drains was modelled by means of full-scale analysis. The numerical analysis was carried out at two case study locations: the pilot test site and the in situ test site. The test sites comprise vertical drain treated and untreated sub-areas that were reclaimed and preloaded under the same conditions. The result of the FEM analysis was compared with that obtained by means of observational methods. The vertical drain performance was verified for the in situ test site by using the value of Ch obtained from back-analysis by the Asaoka method and by FEM with Plaxis

The hydraulic conductivity of Singapore Marine Clay at Changi

The hydraulic conductivity of Singapore Marine Clay at Changi was studied by both in situ and laboratory methods. In situ tests, such as the Cone Penetration Test (CPT), Dilatometer Test (DMT), Self-boring Pressuremeter Test (SBPT) and BAT permeameter test were carried out. Rowe Cells and oedometers were used to determine the horizontal hydraulic conductivity and vertical hydraulic conductivity respectively. Hydraulic conductivity values were found to range between 10-10 m/s and 10-9 m/s. Hydraulic conductivity values in the horizontal direction measured from laboratory Rowe Cell tests were found to be about twice the vertical hydraulic conductivity from oedometer tests. Horizontal hydraulic conductivity values measured from Rowe Cell tests were also higher than those measured from BAT and SBPT but about the same order as values obtained from CPTU and DMT. Most hydraulic conductivity values evaluated indirectly from in situ dissipation tests were higher than direct measured values from BAT permeameter tests. DMT and CPTU gave the highest horizontal hydraulic conductivity values and SBPT yielded values in between. However CPTU, DMT and SBPT dissipation tests were found to be suitable alternative methods for estimating the hydraulic conductivity of clay. The variation of vertical hydraulic conductivity was characterized by the relationship between void ratio and hydraulic conductivity change index which, based on oedometer results, is only C(kv)=0.3e0. The hydraulic conductivity of Singapore Marine Clay at Changi was studied by both in situ and laboratory methods. In situ tests, such as the Cone Penetration Test (CPT), Dilatometer Test (DMT), Self-boring Pressuremeter Test (SBPT) and BAT permeameter test were carried out. Rowe Cells and oedometers were used to determine the horizontal hydraulic conductivity and vertical hydraulic conductivity respectively. Hydraulic conductivity values were found to range between 10-10 m/s and 10-9 m/s. Hydraulic conductivity values in the horizontal direction measured from laboratory Rowe Cell tests were found to be about twice the vertical hydraulic conductivity from oedometer tests. Horizontal hydraulic conductivity values measured from Rowe Cell tests were also higher than those measured from BAT and SBPT but about the same order as values obtained from CPTU and DMT. Most hydraulic conductivity values evaluated indirectly from in situ dissipation tests were higher than direct measured values from BAT permeameter tests. DMT and CPTU gave the highest horizontal hydraulic conductivity values and SBPT yielded values in between. However CPTU, DMT and SBPT dissipation tests were found to be suitable alternative methods for estimating the hydraulic conductivity of clay. The variation of vertical hydraulic conductivity was characterized by the relationship between void ratio and hydraulic conductivity change index which, based on oedometer results, is only Ckv=0.3e0