•Examination of different Mg2+ concentrations in 0.5M Ca(CH3COO)2/urea cementation solution.•Aragonite crystals were precipitated under the involvement of carboxyl groups.•0.01 M Mg2+ can bring about ...40-percentage promotion in UCS of a bio-cemented sample.•Mg2+ can promote aragonite precipitation while inhibit calcite crystallization.
This study examines the magnesium ions effect on carbonate crystal polymorph when Ca(CH3COO)2/urea acts as cementation solution in microbially induced carbonate precipitation (MICP) process. The results of unconfined compressive strength (UCS) indicates that the involvement of Mg ions in Ca(CH3COO)2/urea cementation solution can greatly improve the physical and engineering properties of bio-cemented samples. Compared with the bio-cemented sample without any Mg ions, additional 0.01 M Mg ions in 0.5 M Ca(CH3COO)2/urea solution will contribute to 40% higher UCS, and additional 0.5 M Mg ions in 0.5 M Ca(CH3COO)2/urea solution will make the average UCS twofold higher. While, UCS of the samples treated with MgCl2/urea with poor crystallinity magnesium carbonate is one-tenth of that treated with 0.5 M Ca(CH3COO)2/urea. Furthermore, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) images show that acicular aragonite and rhombohedral calcite are two main types of calcium carbonate crystal precipitated when Ca(CH3COO)2/urea acts as the cementation solution, and the incorporation of Mg ions modifies the crystal polymorph, promoting more aragonite precipitation but inhibiting calcite growth. The mechanism of magnesium ions effect on crystal polymorph is also summarized in the end. The efficiency of Ca(CH3COO)2/urea with a small amount of Mg ions is particularly noteworthy in MICP process.
► High-strength microbial mortar with a UCS up to 55MPa was obtained without cement. ► Splitting tensile strength was measured for both microbial mortar and cement–lime mixed mortar samples. ► Cyclic ...compressive loading tests were performed on both microbial mortar and cement–lime mixed mortar samples. ► The pore-size distribution of microbial mortar and cement–lime mixed mortar samples was measured. ► The crystal formation for in situ microbial induced carbonate precipitation was quantitatively analyzed.
Microbial grouting reinforcement to repair the deterioration of masonry structures involves injecting microorganisms and nutrient solution (a cementation solution) into existing granular system pores to induce the generated calcium carbonate cementation to form a microbial mortar of certain strength. Microbial grouting reinforcement is used when traditional grouting materials, such as lime, cement and epoxy, cannot be employed. In this paper, based on experimental study, the main biochemical factors that affect microbial mortar strength were investigated. In addition, the mixture ratio and laboratory preparation method for high-strength microbial mortars were determined. Microbial mortars of different strengths were successfully produced, through which the maximum uniaxial compressive strength reached 55MPa. The mechanical properties of the microbial mortar, such as uniaxial compressive strength, splitting tensile strength, compressive strength under cyclic loading and uniaxial compressive fatigue, were tested, and the crystal structure of the carbonate cementation and pore-size distribution of the microbial mortar were analyzed. The results indicate that in strength, deformation and durability, this new material is superior to conventional cement–lime mortar. This new type of grouting is ideal for the in situ reinforcement of deteriorated masonry structures. The preparation method for high-strength microbial mortar, the material’s tested mechanical properties and the quantitative relationships of the material’s grouting parameters are reported. The material provides a novel method to reinforce deteriorated masonry structures, particularly historical masonry structures.
•Full-scale TRT and TPT of CFG pile exchangers are performed.•Heat exchange capacity of CFG energy piles is estimated from different power TRT.•Effects of inlet water temperature and flow velocity on ...TPT are studied.•Heat exchange of CFG energy piles varies with different operation modes.•Temperature influence radius of a single CFG pile exchanger is over 4m.
Pile geothermal exchangers are a popular new type of geothermal exchanger for use in ground source heat pump systems due to their technical and cost improvements over traditional borehole geothermal exchangers. An in-situ full-scale study using the thermal response and thermal performance tests (TRT and TPT) is performed to investigate the heat exchange capacity of the cement-fly ash-gravel (CFG) piles usually used in foundations for low to medium high-rise buildings in Beijing. This paper analyzes the influences of the hydration heat of cement, heating power, inlet water temperature, circulating water flow velocity, operation mode, and group-pile effects on the heat exchange capacity of CFG pile geothermal exchangers. The test results can be used for the thermal design of CFG energy piles.
The technology of bio-gronting is a new technique for soft ground improvement. Many researchers have carried out a large number of experiments and study on this topic. However, few studies have been ...carried out on the dynamic response of solidified sand samples, such reducing liquefaction in sand. To study this characteristic of microbial-strengthened liquefiable sandy foundation, a microorganism formula and grouting scheme is applied. After grouting, the solidified samples are tested via dynamic triaxial testing to examine the cyclic performance of solidified sand samples. The results indicate that the solidified sand samples with various strengths can be obtained to meet different engineering requirements, the use of bacteria solution and nutritive salt is reduced, and solidified time is shortened to 1-2 days. Most importantly, in the study of the dynamic response, it is found that the MICP grouting scheme is effective in improving liquefiable sand characteristic, such as liquefaction resistance.
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, a fully coupled thermo-hydro-mechanical (THM) finite element (FE) program for saturated soils is developed for this purpose. The FE formulation accounts for the combined effect of rate and temperature through the novel concept of granular temperature. Simulations of THM coupled validation cases and a series of experimental observations on the soft Bangkok clay are carried out. The obtained numerical results exhibit good agreement with analytical solutions and laboratory measurements. It is found that three fundamental physical mechanisms contribute to the irreversible thermal contraction observed for normally consolidated and lightly overconsolidated clays under drained thermal cycles: (1) the thermal creep excited by mass exchange from adsorbed water to free water; (2) the mechanical creep induced by confining stresses; and (3) the increase in granular packing caused by the thermal expansion of soil particles. The thermal contraction generally stabilizes within a few thermal cycles, as a result of the noticeable reduction in the thermal creep rate. It is further demonstrated that the transient heat transfer and the heating rate can greatly influence the deformation of clays subjected to thermal cycles.
Batter piles are widely used in geotechnical engineering construction. Observations regarding the performance of batter piles in seismic hazards are controversial, and few studies have evaluated ...batter piles in liquefiable and laterally spreading ground. Three centrifuge experiments were performed to gain a better understanding of the performance of batter piles in liquefiable ground and to reveal the influence of the overlying nonliquefiable layer on the batter pile foundation design. The results reveal that for symmetrically placed batter piles, the bending moment of the front pile is greater than that of the rear pile, as a result of the liquefaction-induced lateral deformation in all three cases, and the bending moment reaches its maximum value at the middle of the pile. The presence of the overlying nonliquefiable dense sand layer reduces the potential for liquefaction and lateral spreading of the underlying ground, the settlement and bending moments of the batter piles.
•Dynamic response of batter piles in level liquefiable and laterally spreading soil.•Batter piles show the great resistance to lateral spreading in the model case.•The bending moment of the front pile is greater than that in the rear pile.•The presence of the top dense sand layer reduces the potential of liquefaction.•The total settlement in lateral spreading ground is greater than that in level ground.
The purpose of the present study is to predict and draw up non-grain cultivated land (NCL) susceptibility map based on optimized Extreme Gradient Boosting (XGBoost) model using the Particle Swarm ...Optimization (PSO) metaheuristic algorithm. In order to, a total of 184 NCL areas were identified based on historical records, and a total of 16 NCL susceptibility conditioning factors (NCLSCFs) were considered, based on both a systematic literature survey and local environmental conditions. The results showed that the XGBoost model optimized by PSO performed well in comparison to other machine learning algorithms; the values of sensitivity, specificity, PPV, NPV, and AUC are 0.93, 0.89, 0.88, 0.93, and 0.96, respectively. Slope, rainfall, fault density, distance from fault and drainage density are most important variables. According to the results of this study, the use of meta-innovative algorithms such as PSO can greatly enhance the ability of machine learning models.
Laplace transforms were used in this paper to obtain analytical solutions for the axisymmetric problem under a constant well temperature using the convective heat transfer boundary condition, which ...included the conduction and convection in the aquifer as well as heat exchange at the boundary. This solution curve intuitively illustrates the temperature distribution within the aquifer. The effects of various parameters on this analytical solution were analyzed. According to this parametric analysis there exists a quasi‐steady‐state of temperature distribution in the axisymmetrical situation, which is different from the planar symmetry problem. In addition, the thermal breakthrough increases with the injected rate and decreases with the increasing convective heat transfer coefficient. Our analytical solution matched the results yielded by the numerical simulation quite well.
BACKGROUND AND AIMS: Low phosphorus (P) availability is a major constraint to soybean growth and production, especially in tropical and subtropical areas. Root traits have been shown to play critical ...roles in P efficiency in crops. Identification of the quantitative trait loci (QTLs) conferring superior root systems could significantly enhance genetic improvement in soybean P efficiency. METHODS: A population of 106 F₉ recombinant inbred lines (RILs) derived from a cross between BD2 and BX10, which contrast in both P efficiency and root architecture, was used for mapping and QTL analysis. Twelve traits were examined in acid soils. A linkage map was constructed using 296 simple sequence repeat (SSR) markers with the Kosambi function, and the QTLs associated with these traits were detected by composite interval mapping and multiple-QTL mapping. KEY RESULTS: The first soybean genetic map based on field data from parental genotypes contrasting both in P efficiency and root architecture was constructed. Thirty-one putative QTLs were detected on five linkage groups, with corresponding contribution ratios of 9·1-31·1 %. Thirteen putative QTLs were found for root traits, five for P content, five for biomass and five for yield traits. Three clusters of QTLs associated with the traits for root and P efficiency at low P were located on the B1 linkage group close to SSR markers Satt519 and Satt519-Sat_128, and on the D2 group close to Satt458; and one cluster was on the B1 linkage group close to Satt519 at high P. CONCLUSIONS: Most root traits in soybean were conditioned by more than two minor QTLs. The region closer to Satt519 on the B1 linkage group might have great potential for future genetic improvement for soybean P efficiency through root selection.
Growing evidences have indicated that microRNAs (miRNAs) play a significant role relating to many important bioprocesses; their mutations and disorders will cause the occurrence of various complex ...diseases. The prediction of miRNAs associated with underlying diseases
computational approaches is beneficial to identify biomarkers and discover specific medicine, which can greatly reduce the cost of diagnosis, cure, prognosis, and prevention of human diseases. However, how to further achieve a more reliable prediction of potential miRNA-disease associations with effective integration of different biological data is a challenge for researchers. In this study, we proposed a computational model by using a federated method of combined multiple-similarities fusion and space projection (MSFSP). MSFSP firstly fused the integrated disease similarity (composed of disease semantic similarity, disease functional similarity, and disease Hamming similarity) with the integrated miRNA similarity (composed of miRNA functional similarity, miRNA sequence similarity, and miRNA Hamming similarity). Secondly, it constructed the weighted network of miRNA-disease associations from the experimentally verified Boolean network of miRNA-disease associations by using similarity networks. Finally, it calculated the prediction results by weighting miRNA space projection scores and the disease space projection scores. Leave-one-out cross-validation demonstrated that MSFSP has the distinguished predictive accuracy with area under the receiver operating characteristics curve (AUC) of 0.9613 better than that of five other existing models. In case studies, the predictive ability of MSFSP was further confirmed as 96 and 98% of the top 50 predictions for prostatic neoplasms and lung neoplasms were successfully validated by experimental evidences and supporting experimental evidences were also found for 100% of the top 50 predictions for isolated diseases.
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