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Bacteria, Bio-films, and Invertebrates... the Next Generation of Geotechnical Engineers?

机译：细菌，生物膜和无脊椎动物...下一代岩土工程师？

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The long-standing assumption in the geotechnical community that geotechnical systems are purely abiotic and free of biological influence has been misleading. In recent years this notion has been challenged by overwhelming evidence that biological processes occurring at microscopic scales can influence macroscopic geotechnical properties, even in environments as controlled as man-made fill materials. Biological organisms are pervasive throughout soils, existing at high densities (at least relative to humans) at nearly all length scales. One gram of typical top soil may be home to 10~(12) bacteria, and more than 10~6 bacteria may be present in a single gram of poorly graded engineered granular fill. Larger biological organisms, such as burrowing invertebrates (i.e. worms) can also exist at relatively high densities simultaneously, altering geotechnical properties as they break down large organic compounds for utilization by bacteria and fungi. These bio-geo-chemical and bio-chemo-mechanical processes occur in unison as these organisms strive to live in soil ecosystems. While these organisms may not be purposeful geotechnical engineers, their biological activities alter the engineering properties of soils - stiffness, strength, permeability - that are used for geotechnical design. In recent years an increased awareness of the biological aspects of soils has been a focal point for research, with particular interest in harnessing these natural biological processes for geotechnical engineering benefit. Herein three processes in particular, which range in biogeo-chem-mechanical processes, length scale, and research maturity are investigated. First, the process of bio-calcification through microbial ureolysis is examined, with linkages between bacterial activity, chemical composition, crystalline structure (SEM), geophysical signatures (V_s), and engineering parameters such as strength and permeability are presented. Secondly, the process of slime forming bacteria though aerobic metabolic processes is explored to form a temporary, jello-like, slime that can reduce permeability and dynamic pore pressure generation. Thirdly, the digestion and excretion of fecal pellets from marine burrowing invertebrates is presented, showing a link between pellet structure, burrowing geometry, inter- and intra- soil porosity, and strength.
机译：在岩土工程界，长期以来一直认为岩土系统是完全非生物的，并且没有生物影响，这一直是一种误导。近年来，这一观点受到了压倒性证据的挑战，这些证据表明，即使在像人造填充材料一样受控的环境中，微观尺度上发生的生物过程也会影响宏观的岩土特性。生物几乎遍及整个土壤，以高密度（至少相对于人类）以几乎所有长度尺度存在。一克典型的表层土壤可能是10〜（12）种细菌的宿主，而一克等级不佳的工程颗粒填料中可能存在10〜6种以上的细菌。挖洞的无脊椎动物（即蠕虫）等较大的生物也可以同时以相对较高的密度同时存在，从而改变了岩土工程性质，因为它们分解了大的有机化合物以供细菌和真菌利用。这些生物地球化学和生物化学机械过程同时发生，因为这些生物努力生活在土壤生态系统中。虽然这些生物可能不是有目的的岩土工程师，但其生物活动会改变用于岩土设计的土壤的工程特性-刚度，强度，渗透性。近年来，人们对土壤生物学方面的认识不断提高，已成为研究的重点，尤其是利用这些自然生物学过程获得岩土工程利益。在本文中，特别研究了三个过程，它们涉及生物地球化学-化学-机械过程，长度尺度和研究成熟度。首先，研究了通过微生物尿素分解进行生物钙化的过程，并结合了细菌活性，化学成分，晶体结构（SEM），地球物理特征（V_s）和工程参数（例如强度和渗透性）之间的联系。其次，探索了通过有氧代谢过程形成粘液细菌的过程，以形成一种类似于胶冻状的暂时粘液，这种粘液可以降低渗透性和动态孔隙压力的产生。第三，介绍了海洋洞穴无脊椎动物中粪便颗粒的消化和排泄，显示了颗粒结构，洞穴几何形状，土壤间和土壤内部的孔隙度以及强度之间的联系。

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