Jian Chu

Nanyang Technological University | ntu

Climate change and desertification caused increases in sandstorms and sand movements due to the erosive force of the wind. Wind erosion is a phenomenon depending on the climatic components and surface roughness in arid and semi-arid regions responsible for health and economic loss. The phenomenon is controlled by increasing the resistance of soils...

One-phase-low-pH MICP (Microbially Induced Carbonate Precipitation) or EICP (Enzyme Induced Carbonate Precipitation) is a new biocementation method for soil improvement. This method uses the low pH of bacterial or urease solution to provide a delay for the MICP or EICP process so that the treatment solution can be evenly distributed in soil during...

With rising sea level and demand for more nearshore infrastructures, the current methods for seawall construction may no longer be sustainable. Alternative seawall construction methods need to be developed. When seawall or other coastal defense systems are constructed on soft marine deposits, suction caissons are feasible to be installed into marin...

The accumulation of construction and demolition (C&D) waste in landfills is a global issue which is exacerbated by the impact of rapid urbanization and increased construction activities in metropolitan and regional areas. The recycled sands studied in this research were derived from processed C&D waste from a washing plant located in Melbourne, Vic...

The low conversion of reactive MgO cement (RMC) into hydrated magnesium hydroxy carbonates (HMHCs) due to limited CO2 diffusion towards the sample core leads to inefficient RMC use and low strength development in RMC concrete. This study proposed a novel technique to enhance hydration and carbonation at both the exterior and core sections of RMC co...

Increasingly waste materials or soft soil dredged from sea or river have to be used as fill materials for land reclamation. Although preloading using prefabricated vertical drains (PVDs) has been commonly used as the treatment method for soft soil, this method is time consuming as it can only be applied after all the fill materials have been placed...

The failure mechanism of biocemented sand has been largely speculated based on scanning electron microscopy (SEM) images of biocemented sand after mechanical tests. However, some breakage patterns cannot be directly observed, such as the separation of CaCO3 crystals and the separation of CaCO3 crystals and sand surfaces. A study of the breakage pro...

In Singapore, a large amount of borehole data has been obtained over years from various projects of site investigation. A web-based management system is developed to enhance 3D geological modelling by the AI interpretation of borehole data. A 3D geological model of Singapore is firstly established using available geological information including bo...

One of the latest developments in biocementation is the use of one-phase-low-pH MICP or EICP method as a more effective and efficient alternative to the traditional two-phase method for the treatment of sandy soil. However, the one-phase-low-pH method has its own limitation. The pH of the solution has to be adjusted before every treatment. In this...

The failure of biocemented sand can be attributed to the breakage of biocement 23 and the exfoliation of precipitates from sand surfaces. Therefore, optimizing the mechanical 24 properties of the biocement is one of the methods to improve the performance of MICP for 25 stabilizing sand. Besides, a deep understanding of the properties of biocement i...

Biocement based on a Microbially Induced Calcite Precipitation (MICP) process has emerged to be a promising alternative to cement for soil improvement. A two-phase injection method is commonly used for the MICP treatment of granular soil. However, the samples treated using this method may not be uniform. Recently, an acidified one-phase-low-pH inje...

Soil properties, the chemical composition of cementation solution, injection technique, and environmental conditions have all been extensively studied as variables influencing MICP performance. However, despite the fact that different researchers used different bacterial suspensions, the influence of bacterial suspension type, more specifically som...

Bio-gelation is a new method for improving the hydraulic and mechanical properties of sandy soil through the production of polymeric gel to fill in the pores of soil. In this paper, a study on the engineering behaviour of loose sand treated using this method is presented. A series of permeability and undrained monotonic and cyclic triaxial tests we...

Either microbial or enzyme induced carbonate precipitation (MICP or EICP) has emerged to be alternative to cement-based ground improvement methods. For EICP, either plant urease or bacterial enzyme can be used. The effect of treatments can be different when different methods are adopted. In this study, the soil improvement effects among the three m...

Three-dimensional (3D) geological model, as an effective tool for modelling the complex nature of underground geological conditions, has been used for the design and construction of underground facilities. The accuracy and reliability of the geological information reflected by the 3D model are critical for engineering practitioners to make sound ju...

The location of the interface of geological formations is an important piece of information for tunneling construction. As site investigation data are usually limited, the uncertainties in locating geological interfaces for the sections between boreholes can be large and challenging to estimate. A suitable geostatistical method is thus needed for s...

The spatial variation of the physical-mechanical properties of rock or rock-like materials is an intrinsic characteristic of the materials induced by multiscale material heterogeneities. The Weibull distribution is a widely used statistical model for the characterization of non-uniform mechanical property distribution of rock or rock-like materials...

This paper presents a methodology to construct a water pond in sand using bioslurry layer via the microbially induced car-bonate precipitation (MICP) process. Bioslurry is calcium carbonate crystals containing high-urease active bacteria cells, allowing further microbially induced calcium carbonate precipitation when introducing cementation solutio...

Ocean development is an effective and practical way to address resource issues, such as food, fuel, and land shortage. The current work proposed using kaolin-based biocement to stabilize calcareous sand which is always the main component of the foundations of ocean engineering. Five kinds of kaolin concentrations (0 g/L, 10 g/L, 20 g/L, 50 g/L, and...

Biocement is an emerging construction material via the microbially induced calcite precipitation (MICP) process for soil improvement, which could be produced using waste materials at ambient temperature. This paper investigates the possibility to produce sustainable biocement using industrial waste carbide sludge and urine. Urine was used as the gr...

Geological information such as geological interfaces is important for the design of underground excavation and supporting measures. This in turn requires a method to predict accurately the locations of geological interfaces for the gap areas between boreholes. This study presents a generalized additive model (GAM) to predict the location of the geo...

Urease is a dinickel enzyme commonly found in numerous organisms that catalyses the hydrolysis of urea into ammonia and carbon dioxide. The microbially induced carbonate precipitation (MICP) process medicated by urease-producing bacteria (UPB) can be used for many applications including, environmental bioremediation, soil improvement, healing of cr...

For a long time in the practice of geotechnical engineering, soil has been viewed as an inert material, comprising only inorganic phases. However, microorganisms including bacteria, archaea and eukaryotes are ubiquitous in soil, and have the capacity and capability to alter bio-geochemical processes in the local soil environment. The cumulative cha...

Aims: To investigate the prognostic value of hemoglobin combined with geriatric nutritional risk index (GNRI) scores in patients undergoing postoperative radiotherapy for esophageal squamous cell carcinoma (ESCC). Patients & methods: Patients who underwent esophagectomy and postoperative radiotherapy were included in this retrospective study. Their...

Intensive studies have been carried out to establish a soil improvement method based on the microbial induced carbonate precipitation (MICP) process. However, controlling the reaction rate of the MICP process to achieve optimized improvement is still a challenging task. In this paper, a new method involving use of urease inhibitor N-butyl-thiophosp...

The cover image is based on the Research Article Formulation and implementation of an elastoplastic constitutive model for sand-fines mixtures by ZengChun Sun et al., https://doi.org/10.1002/nag.3282.

Microbial geotechnology or biogeotechnology is a new branch of geotechnical engineering. It involves the use of microbiology for traditional geotechnical applications. Many new innovative soil improvement methods have been developed in recent years based on this approach. A proper understanding of the various approaches and the performances of diff...

The microbial-induced calcium carbonate precipitation (MICP) is a hot research topic in recent years, however, the understanding of its spatiotemporal evolution is still insufficient. This paper aims to investigate the spatiotemporal evolution process by designing a conceptual microfluidic chip within large and small pores and using a visualized ex...

Sand-fines mixtures are commonly used engineered materials, and their mechanical behavior is significantly affected by density, confining pressure, as well as fines content. Although many laboratory tests have been performed on sand-fines mixtures, few works have been conducted on its constitutive law. To adequately describe the mechanical behavior...

The spatial information of rockhead is crucial for the design and construction of tunneling or underground excavation. Although the conventional site investigation methods (i.e. borehole drilling) could provide local engineering geological information, the accurate prediction of the rockhead position with limited borehole data is still challenging...

This technical note aims to investigate the effects of biotreatment on the response of a concrete model pile embedded in poorly graded sand through lateral loading tests. The bending moment profiles along pile length were obtained from strain gauges collected during the pile load tests. The pile deflection and soil resistance were derived from a be...

This paper includes an investigation of the thermal conductivity of biocemented soils to better understanding the regimes of heat transmission through soils treated by microbially induced calcium carbonate precipitation (MICP). A series of thermal conductivity tests using the transient plane source method (TPS) was performed on biocemented silica s...

The commonly used data reduction methods to determine shear wave velocity (Vs) require the depth interval of the Vs profile to be the same as the in-situ testing interval. The Vs values derived in this way are the mean values within the depth intervals. However, the in-situ multilayer interfaces do not always coincide with the predetermined testing...

This study evaluated the performances of various autocorrelation function (ACF) models in predicting the geological interface using a well-known conditional random field method. Prediction accuracies and uncertainties were compared between a flexible Matérn model and two classical ACF models: the Gaussian model and the single exponential model. The...

To effectively stabilize coarse sand, bentonite was introduced in microbially induced 3 carbonate precipitation (MICP) grouting. Varying concentrations (0 g/L, 20 g/L, 40 g/L and 80 4 g/L) of bentonite were added to bacterial suspensions (BSs), which were magnetically stirred 5 to form bacterial-bentonite suspensions (BBSs). Then, coarse sand speci...

We used three-dimensional finite element analysis to simulate an X-shaped cast-in-situ concrete (XCC) pile-supported embankment with asphalt pavement under the load of moving vehicles. We investigated the dynamic stress transfer mechanism, the trapping effect of the embankment and XCC piles, and the asymmetric distribution of dynamic stress around...

Clayey soils in the vicinity of energy geostructures may be exposed to long-term periodic thermal cycles. The creep and consolidation behaviors of the clayey soils can be both rate-dependent and temperature-dependent, and the underlying physical mechanisms are merely investigated theoretically. In this study, based on the theory of thermodynamics,...

The outbreak of the coronavirus disease 2019 (COVID-19) pandemic not only has created a health crisis across the world but is also expected to impact negatively the global economy and societies at a scale that is maybe larger than that of the 2008 financial crisis. Simultaneously, it has inevitably exerted many negative consequences on the geoenvir...

Calcareous sands have abundant intraparticle pores and are prone to particle breakage. This often leads to poor engineering properties, which poses a challenge to coastal infrastructure construction. A study using bio-cementation to improve the engineering properties of calcareous sand is presented in this paper. The macro- and microscopic properti...

Microbially induced carbonate precipitation (MICP) has been actively investigated as a promising method to improve soil properties. A burning issue impeding its wide application is the severe spatial inhomogeneity of the CaCO3 distribution. Inspiring by the temperature sensitivity of the bacteria activity, a temperature-controlled one-phase MICP me...

Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand by biocement and Portland cement is presented. Drained triaxial tests were carried out on both cement- and biocement-treated sand. The yielding of cemented sand is largely...

The low hydration and carbonation of reactive MgO cement (RMC) under ambient conditions causes prolonged setting and low compressive strengths (~4 MPa). This study proposed a unique technique which led to the enhancement of the hydration and carbonation processes via the synergistic combination of microbial carbonation process (MCP) with a hydratio...

Microbial induced carbonate precipitation has been widely used in the biomineralization of heavy metals Cd²⁺. However, the low Cd-tolerance of ureolytic bacteria limits the applications with only low Cd²⁺concentrations. In this study, we discovered a simple approach to significantly enhance the Cd²⁺ resistance of ureolytic bacteria through an immed...

A homogeneous microfluidic chip was used to investigate the pore-scale characteristics during the process of microbially induced calcium carbonate precipitation (MICP). An image-processing scheme was developed to measure the projecting areas of the precipitated calcium carbonate. Calcium carbonate first precipitated on the bacterium side before spr...

This paper presents a new microbial technique for soil improvement through microbially induced carbonate precipitation (MICP) incorporating with reactive magnesia cement (RMC). Through a microbially induced carbonate precipitation (MICP) process, hydrated magnesium carbonates (HMCs) are produced due to biological carbonation of hydrated RMC, which...

The calcareous sand foundation may be liquefied to cause structural damages under dynamic loadings such as earthquakes and waves. The microbially induced calcite precipitation(MICP) can enhance the strength of the calcareous sand foundation on a large scale and improve its liquefaction resistance. In this paper, the dynamic pore pressure developmen...

Biocementation of soil using microbial-induced carbonate precipitation has become a new approach for soil treatment. The biocemented sand behaves differently from uncemented sand. One of the major differences is the stress-dilatancy behavior. In this paper, the experimental data obtained from isotropically consolidated drained triaxial tests are pr...

Microbially induced calcite precipitation (MICP) is used for bio-cementation of calcareous sand using microbial metabolism to generated calcite precipitation. This technology has been proposed for sealing damage in geological reservoirs, repair of cracks in stone buildings, and strengthening of foundations in coastal engineering. To test the stabil...

A series of undrained cyclic triaxial tests are carried out for calcareous sand treated by temperature-controlled MICP (microbially induced calcium carbonate precipitation) technology, and the dynamic strength characteristics of MICP-treated calcareous sand are thoroughly investigated. The in-depth discussion is conducted for the effects of bioceme...

Concentration of cementation solution (CCS) is one of the key factors influencing the cementation effect on soil improvement through the microbially induced carbonate precipitation (MICP) process. To precipitate more calcium carbonate per treatment, a higher CCS is needed. However, the MICP process may be retarded or even terminated with an increas...

Enzyme induced carbonate precipitation (EICP) is an emerging soil improvement method using free urease enzyme for urea hydrolysis. This method has advantages over the commonly used microbially induced carbonate precipitation (MICP) process as it does not involve issues related to bio-safety. However, in terms of efficiency of calcium carbonate prod...

A new treatment, microbially induced calcium carbonate precipitation (MICP) with micro-particle improved nucleation (MICPMPIN), is introduced to improve the performance of MICP technology for the stabilization of coarse sand. A certain amount of kaolin is augmented into the bacterial suspensions to obtain immobilized bacterial slurry, then the bact...

Seismic cone penetration test (SCPTu) has been used for the determination of seismic velocities and the corresponding stiffness parameters of intact soils. In this study, SCPTu tests are carried out at three reclaimed land sites in Singapore for characterizing the reclaimed fill and the underlying marine clay. New methods for interpreting the downh...

The particle breakage and compressibility behavior of sands treated with microbially induced carbonate precipitation (MICP) has been investigated using oedometric compression tests. The acid washing technique was used to obtain the calcium carbonate (CaCO3) content and facilitate quantification of particle breakage by measurement of the particle si...

Microbial-induced carbonate precipitation (MICP) methods have been developed in recent years for soil improvement to simultaneously increase the shear strength and reduce the permeability of soil or aggregate. However, this method is difficult to use for aggregate because many more injections are required. This technical note proposes a new biogrou...

Biocementation using a microbially-induced carbonate precipitation (MICP) process has become a new method for soil improvement. However, this method produces ammonia gas which is not desirable. A new biocementation method using a microbially-induced struvite precipitation (MISP) process is proposed in this paper. The main cementation components pro...

The calcareous sand foundation may be liquefied to cause structural damage under dynamic loads such as earthquakes and waves, and the microbially induced calcite precipitation (MICP) can strengthen calcareous sand foundation on a large scale and improve its liquefaction resistance. In this paper, the dynamic pore pressure development of MICP-treate...

This paper presents a microbial technique for soil improvement through microbially induced carbonate precipitation (MICP) as well as the incorporation of reactive magnesia cement (RMC). Several parameters including the RMC content and urea content within MICP process, as well as the water content were investigated. The performance of RMC samples wa...

Construction over soft soil is a challenge as the ground can be too soft to work on it. To overcome this, a working platform has to be formed before any soil improvement work can be carried out. One of such methods was proposed by Broms (1987) which uses geotextile and sand berms. In this paper, a modified Broms' method is proposed to use geotextil...