-to protect tree roots and underground infrastructure in urban areas-.

Underground, urban trees have less and less space to expand their root systems due to pipelines, pipes and building walls. Also, an ever-increasing proportion of sealed and waterproofed surfaces makes it difficult for trees to absorb water and nutrients, as well as to exchange air. The soil structure of the sometimes poorly compacted pipeline zones, on the other hand, forms an expanded habitat for the root system. Roots, however, not only grow into existing pore spaces in the soil, but also into leaky pipe joints, where they can cause blockages, stresses and major leaks or cracks. Costly excavations, tree-damaging root capping and time-consuming repairs are the result. This inevitably leads to the task of working out a balanced coexistence of trees and underground infrastructure. This is the starting point for the research project funded by the Deutsche Bundesstiftung Umwelt (DBU), in which self-compacting backfill materials with high root resistance are to be developed as an alternative to compactable fill materials using the excavated soil preferentially to protect tree roots and underground infrastructure in urban areas. These are to encase pipes and lines without stress or voids and without mechanical compaction, and to prevent tree roots from growing into the line zones. On the one hand, this protects pipes and lines from root ingrowth and damage in the form of tension loops or pressure pads, and on the other hand it also protects trees from ever new excavations and root capping during pipe rehabilitation.