Fungi-Biopolymer synergistic application in soil stabilisation

世界各地的建筑行业都在使用像水泥这样的高能量和碳排放稳定剂来稳定有问题和脆弱的土壤，这些土壤用于发展土基础设施。虽然水泥的加入提高了土壤的强度和耐久性，但它对地面造成了重大的环境影响，并降低了土壤可重复使用的前景。为了限制碳排放和保护有限的自然资源，建筑行业必须立即寻找水泥和类似土壤稳定材料的合适替代品。在最近的过去，有一个日益增长的兴趣在土木工程中使用生物岩土工程过程的地面改造。生物岩土工程过程使用生物生产的过程或产品来稳定土壤。生物稳定技术，如真菌和生物聚合物稳定技术，在土壤稳定方面具有巨大的潜力，可以取代水泥，但尚未在文献中进行彻底的研究。菌类如平菇（Pleurotus ostreatus）在有机基质存在的情况下接种到土壤中形成菌丝网络，导致菌丝颗粒聚集，对土壤产生拒水性。土壤中的有机基质是控制菌丝网络生长动力学的关键成分，它关系到菌丝网络的总生物量、渗透深度和生长速率。因此，真菌稳定土壤的效果直接取决于真菌接种土壤时使用的有机基质的类型。另一方面，瓜尔胶和黄原胶等多糖生物聚合物与水混合在土壤中会形成三维多孔结构，称为“水凝胶”，使土壤颗粒相互连接，提高土壤的强度和耐久性。与水泥相比，只需要少量的生物聚合物就可以稳定大量的土壤，而且稳定的土壤有可能被重复利用。然而，当暴露于较长时间的饱和时，生物聚合物稳定的土壤会导致水凝胶的部分或全部溶解，导致土壤强度降低。为了确保有效的生物聚合物土壤稳定性，有必要确保水凝胶能够抵抗水侵入。考虑到生物聚合物可以作为菌丝网络生长的基质，而真菌可以诱导土壤的拒水性，确保水凝胶可以保持稳定，防止水侵入，当这些方法协同作用时，两种生物稳定技术的需求可以得到解决。考虑到真菌种类和生物聚合物的多样性，本研究提出了真菌和生物聚合物之间独特的协同作用的优化设计。这项研究的结果将导致开发一套真菌-生物聚合物组合作为土壤稳定剂。此外，这些发现可以使现场工程师以不同的方式改造地面，这是水泥无法实现的，从而为地面改造带来了新的机会。

Construction industries worldwide use high-energy and carbon-emitting stabilisers like cement to stabilise problematic and weak soils used in developing earthen infrastructure. Whilst the addition of cement though has improved soil strength and durability, it causes a significant environmental impact on the ground and reduces the prospects of soil reusability. To limit carbon emissions and conserve limited natural resources, it is pivotal for the construction industry to immediately seek suitable replacements for cement and similar materials for soil stabilisation. In the recent past, there is a growing interest in civil engineering to use bio-geotechnical processes for ground modification. Bio-geotechnical processes use biologically produced processes or products for soil stabilisation. Bio-stabilisation techniques like fungi and biopolymer stabilisations have huge potential to replace cement in soil stabilisation but have not been thoroughly investigated in the literature. Fungi species like Pleurotus ostreatus on inoculation to soil in presence of organic substrate form hyphal networks which cause particle aggregation and induce water repellency to the soil. The organic substrate in the soil is the crucial component which controls the growth kinetics of the hyphal network concerning its total biomass, penetration depth and growth rate. Thus, the efficacy of the fungi soil stabilisation is directly dependent on the type of organic substrate used during the inoculation of fungi into the soil. On the other hand, polysaccharide biopolymers like guar and xanthan gums when mixed in soil with water form three-dimensional porous structures called 'hydrogels' that interlink soil particles and improve soil strength and durability. Only small quantities of biopolymer are required to stabilise large quantities of soil in comparison to cement and further, the stabilised soil has potential to be re-used. However, biopolymer-stabilised soils when exposed to longer periods of saturation lead to the partial or full dissolution of hydrogels causing a reduction in soil strength. To ensure effective biopolymer soil stabilisation, it is necessary to ensure the hydrogels can be made resilient against water intrusion. The needs of the two bio-stabilisation techniques can be addressed when these methods are in synergy considering biopolymer can act as a substrate for hyphal network growth, while the fungi can induce water repellency to the soil ensuring hydrogels can remain stable against water intrusion. Considering the wide variety of fungi species and biopolymers available, the distinctive synergy between fungi and biopolymers is proposed to be optimally engineered in this study. The outcomes of the study will lead to the development of a suite of fungi-biopolymer combinations as soil stabilisers. Further, the findings can enable field engineers to modify ground in different ways which cement cannot perform leading to newer opportunities in ground improvement.