Karst sinkhole is a unique natural phenomenon that is caused by groundwater movement inside soluble ground rocks. However, in today’s cities, karst phenomena are usually associated with collapses of roads and entire settlements. A number of strategies are used to explore karst topography; however, sinkhole hazards in karst areas, assessing karst presence and their management are not well understood.
Fig. 1. Karst sinkholes in urban environment (from left to right): Berezniki (Russia), Guatemala, Israel
Mycokast is a new generation of urban materials based on karst soil or stone composite and fungal spores that is able to `self-repair` in extreme conditions. The work aims to utilize biotechnologies in relation to materials with a high probability of destruction. It is noted that a material based on the simplest microorganisms has the greatest flexibility and resilience. The focus is on fungal spores, which expand in soil cracks under moisture and precipitate calcite reproducing karst limestone. Firstly, this technology does not require human intervention, when a damage occurs both in architectural wall and in sinkhole`s wall. Secondly, it is interesting to note that karst soils has the same carbonate component (CaCO3) that microorganisms produce reacting with calcites and water. Moreover, the low cost of local fungal material and lack of need for additional reagents, as well as favorable survival conditions give the priority to fungi over bacteria.
To have the reliable result, the soil`s local components of the karst area along the Noksa river in Kazan were tested. The soil`s components and local biota, as well as parameters of karst ravine and climate conditions were fixed.
THE PROJECT WAS DEVELOPED WITHIN THE PROTOTYPING FUTURE CITIES MASTER PROGRAM AND THE AMERICAN BIODESIGN CHALLENGE PROGRAM
The methodology of the experimental study includes the observation of the fungus growth in liquid and solid substrates based on karst soil, dolomite, ash, moss, fungal spores and their strength assessment. A quality of Mycokarst modules was evaluated by strength test, as well as visually by mycelium and calcite patterns. A primary resilient modules with calcite layer were demonstrated on 21 day. After 6 months, a new living material increased in strength by 2.5 times. A final material is extremely hard, shatter-resistant and can handle compression forces of more that 40 MPa. The hypothesis was confirmed – fungal spores produce two patterns – carbonate minerals that provide karst resilience and elastic living matter that provide reproduction of the system as a whole.
Fig. 2. `Self-healing` karst sinkhole with fungal spores. Principle. Fig. 3. Karst ravine along the Noksa River, Kazan city. Section. Materials and biota. Fig. 4. Karst ravine along the Noksa River, Kazan city. Plan
Fig. 5. Experimental study. Tests. Fig. 6. Strength test of the Mycokarst material based on mixed karst soil with dolomite flour. Mycokarst resilient modules
Fig. 7. Mycokarst resilient modules
Mycokast is promoted as a new generation of urban materials that is able to `self-repair` in extreme conditions and, as a result, shape a unique morphology without human intervention. Mycokarst system can be realized by robotics technologies and drones in reality allowing to save labor and time for execution. Moreover, this biointegrated material allows not only to save on manufacture of concrete for construction and engineering strategies, but also realizes a smart solution for modern challenges. The system can be represented in `archetypes` depending on urban and social needs. The breakthrough of the work is that the technology of managing urban `non-programmable` phenomena, demonstrated on the example of karst, can be applied both to geological and architectural materials.
Fig. 10. Mycokarst system evolution
Fig. 8. Mycokarst patterns. Fig. 9. Mycokarst system scales. Prototypes: a – modules, b – wall, c – ravine (sinkhole)
Fig. 11. Mycokarst archetypes (from left to right): Open sinkhole with Mycokarst walls, Covered sinkhole on road, Mycokarst architecture (museum of nature), Mycokarst-based object (grotesque)