Incorporation of Optical Density into the Blending Design for a Biocement Solution

The engineering practices for applying the microbial precipitation of carbonates require a design of the blending biocement solution (BCS). The BCS is usually blended with concentrated strains NO-A10, reaction media, such as urea and CaCl2, and a solvent, i.e., water or seawater. To characterize the BCS, the unknown microbial characteristics, such as the cell viability, are complex factors. Therefore, the optical density (OD) was redefined as Rcv OD*, in which OD* was the tentative OD of the BCS used and Rcv was the conversion rate concerning the cell viability. To determine Rcv values, a standard precipitation curve based on the precipitation rate at 24 h was determined. It was found that the curve was expressed by λ1 OD+ λ2 OD2, in which λ1 and λ2 were 8.46 M and −17.633 M, respectively. With this, the Rcv and OD values of unknown BCS were estimated from the results of precipitation tests using arbitrary OD* values. By extending the testing time, the second order term of OD or OD* was negligible. Accordingly, the precipitation amount is expressed as 8.46 OD, in which the OD can be estimated by precipitation tests using arbitrary OD* values of BCSs. Unless the Ca2+ value is dominant, the optimum blending of BCS can be determined by OD. Thus, it is concluded that the blending design of BCS is achieved using 8.46 OD, or 8.46 Rcv OD*, and the standard precipitation curve was defined in this study

Effects of carbonate on cementation of marine soils

This study shows that calcium carbonate plays an important role as a cementing agent of various marine sediments. The measured vane shear strength of marine soil samples is shown to vary with depth and is strongly correlated with the calcium carbonate content. The results show that an increase in calcium carbonate of 1% causes an increase in shear strength of about 10 kPa. Moreover, under accumulating self‐weight, consolidation is found to be enhanced by calcium carbonate. It was also found that both the cementation and condensation due to calcium carbonate are the major factors accounting for the strength development of marine sediments, beside consolidation. These effects are often greater than those due to grain size effects

EJECTION OF SMALL SEDIMENTARY PARTICLES INTO A CYLINDRICAL BATH BY SWIRL MOTION OF BUBBLING JET

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Concept of hybrid embankment

Concept of hybrid embankment. An innovative technique which is similar to a natural process, i.e., biogeochemical (carbonate) diagenesis, is proposed to construct a hybrid embankment. In this study, the hybrid embankment is defined as a soil embankment which has a microbially induced framework structure of sand sheets and columns in the soft soil matrix. The sand materials are cemented with magnesium-calcite or dolomite, induced by ureolytic microbes. To design and construct hybrid embankments, fundamental problems, such as feasibility in terms of stability, geoenvironmental engineering practices, etc., are examined and discussed. It was shown that the hybrid embankment can be environmentally friendly and also can contribute solving technical and financial problems encountered in actual practice.Koncepcja nasypu hybrydowego. W artykule przedstawiono propozycję budowy nasypu hybrydowego z wykorzystaniem wzmocnienia podobnego do naturalnego procesu biogeochemicznej (węglanowej) diagenezy. Korpus nasypu hybrydowego stanowi grunt słaby z poziomymi wkładkami i kolumnami z piasku wzmocnionego cementacją węglanową wywołaną działaniem drobnoustrojów. Piasek w poziomych wkładkach i kolumnach jest wzmocniony kalcytem magnezowym lub dolomitem wytworzonym przez drobnoustroje ureolityczne. W celu zaprojektowania i zbudowania hybrydowego nasypu omówiono problemy związane ze statecznością nasypu i wykonaniem jego wzmocnienia. Wykazano, że nasyp hybrydowy jest przyjazny środowisku i może przyczynić się do rozwiązania problemów technicznych i finansowych napotykanych przy wykorzystaniu gruntów słabych do budowy nasypów

Evaluation of the Undrained Shear Strength of Organic Soils from a Dilatometer Test Using Artificial Neural Networks

The undrained shear strength of organic soils can be evaluated based on measurements obtained from the dilatometer test using single- and multi-factor empirical correlations presented in the literature. However, the empirical methods may sometimes show relatively high values of maximum relative error. Therefore, a method for evaluating the undrained shear strength of organic soils using artificial neural networks based on data obtained from a dilatometer test and organic soil properties is presented in this study. The presented neural network, with an architecture of 5-4-1, predicts the normalized undrained shear strength based on five independent variables: the normalized net value of a corrected first pressure reading (po − uo)/σ′v, the normalized net value of a corrected second pressure reading (p1 − uo)/σ′v, the organic content Iom, the void ratio e, and the stress history indictor (oc or nc). The neural model presented in this study provided a more reliable prediction of the undrained shear strength in comparison to the empirical methods, with a maximum relative error of ±10%

SWIRL MOTION CAUSED BY TOP LANCE GAS INJECTION IN BOTTOMLESS CYLINDRICAL VESSEL

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