New understandings on initiation and evolution of disasters in deep underground

The editors wish to highlight the articles appearing in this issue. The first article, entitled “New physics of supersonic ruptures” by Boris G. Tarasov, concerns the development of a new theory on the potential occurrence of ruptures after deep underground earthquakes. Two other articles belong to our first special theme of “Disaster evolution in deep underground.” The final two articles introduce a nonlocal damage fracture phase-field model for rock-like materials and the gas–liquid displacement in microcleats for mass transfer through gas- or water-driven displacement. These five papers indeed explore various aspects of deep underground science and engineering and constitute an integral component of deep underground fundamentals.

The research paper “New physics of supersonic ruptures” by Professor Boris G. Tarasov systemically summarizes his long-term research outcomes on the shear rupture mechanism of a fan-shaped structure deep underground (at seismogenic depth). This shear rupture mechanism involves extraordinary mechanical properties and energy transfer. Based on new experimental evidence in laboratory tests and some field monitoring behaviors of deep underground ruptures, this article highlights four important findings. First, a fan-hinged rupture occurs in intact rocks or pre-existing extremely smooth interfaces with a different mechanism, which displays such features as abnormally high energy supply and release as well as extremely low friction. Second, a fan-shaped structure is the key element that represents the source of rupture and consists of an echelon of rock slabs formed by tensile cracking. Third, the fan-shaped structure has almost zero shear resistance, amplified shear stress above the rock strength, abnormally high energy release, and new physics of energy supply to the supersonic rupture tip. Finally, super-shear and supersonic ruptures are observed on extremely smooth interfaces in laboratory conditions. A question commonly raised is, “Why a fracture can be initiated and propagated in grand depth where the in situ stress is so high.” This new physics of supersonic ruptures can cast some light on tackling the above question and guide researchers to observe the deep underground behaviors via unconventional geomechanics. This is an interesting attempt to understand the complex fracturing behaviors deep underground and may thus be beneficial for the development of a knowledge system for deep underground science and engineering.

The two articles from the special theme on “Disaster evolution in deep underground” are entitled “Energy-based analysis of seismic damage mechanism of multianchor piles in tunnel crossing landslide area” and “Triaxial creep damage characteristics of sandstone under high crustal stress and its constitutive model for engineering application.” These articles explore the disaster initiation and evolution in deep underground environments involving energy transfer and dissipation. The two articles analyze the local damage and overall damage of seismic effects on a multianchor pile system and a lined tunnel, with the focus placed on the interaction between ground motion and engineering activity.

The final two papers are entitled “A modified phase-field model for rock-like materials” and “visualizing experimental investigation on gas–liquid replacements in a microcleat model using the reconstruction method.” The first article concerns the nonlocal damage fracture constitutive model of rock-like materials under a complex stress environment with the phase-field method. The model incorporates both plastic strain energy and deformation heterogeneity into the rock deformation analysis. The second article focuses on the mass transfer of a two-phase flow within microcleats. The microcleat flow is achieved through microscale experimental observations and measurements. Both studies explore the deformation and failure mechanisms of rocks and the mass transfer of microfluids in rocks under high crustal stress, thus constituting an integral component of deep underground science fundamentals.

So far, Deep Underground Science and Engineering (DUSE) has published four issues to achieve a complete publication cycle comprising 37 articles. These articles cover all six key topics stated in the inaugural issue of the journal. The coverage of the subject matters is as follows:
  • 1.

    Exploration/extraction of georesources, including deep mining and aggregate mining, rock bursts, deep underground surveys, and induced seismicity.

  • 2.

    Energy extraction and storage, including oil and gas exploration, petroleum geomechanics, shale gas, hydrofracking, enhanced geothermal systems, pumped storage hydropower, compressed air energy storage, and underground hydrogen storage.

  • 3.

    Underground infrastructures, including deep underground space, hydropower engineering, tunnels, underground storage, oil storage, liquid natural gas storage, and rock caverns.

  • 4.

    Geoenvironments and waste geological disposal, including underground carbon storage, geological carbon sequestration, carbon mineralization, nuclear waste disposal, coupled thermal-hydraulic-mechanical-chemical processes, fluid flow, and deep biosolid injection.

  • 5.

    Research and testing space in deep underground, including deep underground laboratory, geosciences, biosciences, subsurface imaging, transparent earth, induced fracturing, fault–slip modeling, fracture network engineering, and subsurface engineering.

  • 6.

    Planning, design, and construction technology for underground space and engineering, including health and safety, resilience, deep drilling, geohazards, geophysical surveys, cost–benefit analysis, and underground blasting.

The current publication data show that the distribution of subject matter for DUSE-published articles is uneven and there is room for improvement to cover more hot topics in deep underground science and engineering. In the field of exploration/extraction of georesources, most articles are related to engineering geology, underground engineering and technology, and the environment. Questions on our mission arise again: What is “deep underground science and engineering”? What should be its contents and future evolution? What types of articles should be included in our journal? To answer these questions, collaborative efforts are solicited from the deep underground research and engineering community globally. The community can explore these problems from various aspects and different angles. DUSE definitely warmly welcomes articles to expand the current domain and knowledge in deep underground science and engineering.