In recent years, an ion-adsorption type REE deposit has been discovered for the first time in the weathering crust of epimetamorphic rocks in Ningdu County, Jiangxi Province, which provides a new idea for the exploration of ion-adsorption-type REE deposits. However, most previous studies on the ore-forming parent rocks of ion-adsorption-type REE deposits have focused on granites and volcanic rocks, while studies on epimetamorphic rocks remain extremely scarce. In this paper, petrographic analysis of epimetamorphic rocks, LA-ICP-MS U–Pb dating and trace element analysis of zircon and apatite were conducted on the metamorphic tuff from the Kuli Formation in Ningdu County, Jiangxi Province, so as to constrain the formation age and tectonic dynamic setting of the rock mass, investigate the petrogenesis and material source of the rock mass, and reveal the metallogenic potential of the rock mass. The results of zircon and apatite U–Pb dating show that the protolith of the metamorphic tuff from the Kuli Formation formed at ca. 700 Ma, representing a product of mid-Neoproterozoic magmatic activity. The protolith restoration of metamorphic rocks suggests that the protolith of the metamorphic tuff from the Kuli Formation is magmatic rock. The estimated results of zircon Ti thermometry indicate that the magmatic crystallization temperature ranges from 623 to 723 °C, with an average value of approximately 696 °C, and the calculated zircon oxygen fugacity values vary from −18.7 to −9.4, with an average of −13.8, implying that the rock formed under conditions of relatively low temperature and high oxygen fugacity. The correlation diagrams of trace elements and element ratios in zircon and apatite reveal that the magmatic evolution involved extensive fractional crystallization of minerals such as zircon, monazite, apatite, titanite, rutile, and plagioclase during the formation of the rock mass. The discrimination diagrams of trace elements in zircon and apatite demonstrate that the metamorphic tuff from the Kuli Formation was formed in a continental margin arc or arc-related orogenic belt, and the magmatic source is characterized by crust–mantle mixing. Combined with previous research findings on regional tectonic-magmatic activities, it can be concluded that the metamorphic tuff from the Kuli Formation was formed in a tectonic setting of back-arc extension and intra-arc rifting caused by the rollback of the subducting oceanic slab. The upwelling of the asthenospheric mantle induced the partial melting of arc-derived sediments in the continental crust, which was subsequently mixed with mantle-derived magma, ultimately generating the parent magma of the metamorphic tuff. The metamorphic tuff from the Kuli Formation in Ningdu County, Jiangxi Province, has high REE abundance and relatively easily weathered REE mineral assemblages, which can provide sufficient material sources for ion-adsorption REE mineralization and have a great metallogenic potential for ion-adsorption REE deposits.

Problem statement. For conditions of asymmetric loads on underground structures caused by uneven weakening of rocks due to flooding and other natural and man-made factors, issues of substantiating rational forms and sizes of injection hardening zones require further comprehensive studies combining geomechanics, materials science and optimization methods. Purpose of the study. Justification of the parameters of injection rock hardening zones to improve the safety level of underground workings and buried structures under conditions of asymmetric loads on the support. Methods. Generalization of data on the asymmetry of loads on the support of underground structures; methodology for assessing the rock massif destruction; mathematical modeling using the finite element method. Research results. Hardening of rocks around underground workings and buried structures allows to reduce the probability of cracks, prevent the development of deformations and increase the overall resistance of objects to the impact of operational and natural loads. The issue of substantiation of rational forms and sizes of injection hardening zones for conditions of asymmetric loads on underground structures which are caused by uneven weakening of rocks due to flooding and other natural and man-made factors requires further research. The features of the formation process of loads asymmetry on the support of the underground structures are determined. The method of assessing the state of the polymer-saturated rock massif and forecasting its changes under the influence of certain measures to strengthen the rocks around the underground structure is substantiated. It has been established that rock hardening by means of injection and other hardening technologies allows for effective compensation of supporting deficiencies without a significant increase in capital expenditures. In addition, the use of various configurations and arrangement schemes of hardening zones allows for flexible adaptation to specific geological conditions, redistribution of stresses in rocks, reduction of their concentrations in potentially hazardous zones, prevention of local collapses, deformations and water inflows, which ensures long-term safe use of underground structures. For conditions of uneven loads on the supports, an asymmetric shape of the hard-ened zone is proposed, which can be used as a reserve for increasing the stability of the underground structure. It is established that the nearly elliptical shape of the hardened zone as an element of rock pressure control ensures an in-crease in the stability of the underground structure due to a 10‒35 % reduction in the inelastic deformation zone and a 0,5‒3,0 m deep displacement of the asymmetric support pressure zone. The displacement of the roof of the underground workings is reduced by 6‒13 % of the total displacements, and the workings floor by 7‒23 %. Scientific novelty. For the first time, in order to increase the level of safety in the operation of underground workings and buried structures under conditions of asymmetric loads on the support, patterns of changes in maximum principal stresses have been established when using various nearly elliptical shape of injection rock hardening zones. Practical significance. The proposed configurations of injection hardening zones reduce stress concentrations in rocks, which helps prevent sudden deformations of supports and ensure long-term safe use of underground structures.

Correction: Experimental Investigation and a Method of Calculating Bearing Capacity for Jointed Rock Masses Under Excavated and Unexcavated Conditions

Addressing the engineering challenge of creep instability in weakly cemented fractured sandstones within extremely soft coal-bearing formations under long-term loading in western mining areas, using weakly cemented sandstone from a coal mine in Xinjiang as the study subject. This research employs uniaxial graded loading creep tests combined with full-information acoustic emission technology and DIC high-speed strain field observation to investigate the creep deformation patterns (The full name of “DIC” is the three-dimensional high-speed dynamic and static stress–strain analysis system of the DIC strain field measurement and analysis system. For the convenience of expression, this system will be uniformly referred to as DIC in the following text), damage evolution characteristics, and failure mechanisms of sandstone under intact, pre-fabricated 30° fractures, and pre-fabricated 60° fractures. Results indicate: Fractures significantly weaken rock strength and long-term stability. Unfractured specimens primarily exhibit columnar splitting tensile failure, while pre-fractured specimens show pronounced shear failure. Shear cracks accounted for 83.67% of failures in 30° pre-fractured specimens and decreased to 63.44% in 60° pre-fractured specimens. Intact specimens exhibited acoustic emission ringing responses during accelerated creep stages, whereas fractured specimens showed ringing responses as early as the first loading stage. During graded loading, ringing counts in pre-fractured specimens continuously accumulated, with cumulative counts significantly exceeding those of intact specimens. Pre-fabricated cracks induced significant stress concentration effects at the ends, causing failure cracks to propagate preferentially along the crack direction and forming a non-uniform deformation field bounded by the crack. The study revealed the micro-macro evolution patterns of progressive damage during creep in extremely weak fractured rock, providing theoretical support for early warning and control technologies against creep instability in tunnel rock masses of weakly cemented strata in western regions.

Dynamic failure mechanisms of anchored rock mass in complex geology: Insights from laboratory experiments and FDM–DEM coupled numerical simulations

Simulation Study of the Mechanical Properties of Hollow Rock Masses under Varying Aperture Angles and Confining Pressures

Reconstruction and upscaling of local rock mass joint networks based on SinGAN

EKTFD: Precise-guided empirical knowledge and time-frequency domain data joint-driven machine learning method for rock mass intelligent perception

Exploring multiscale videogrammetry techniques for analyzing rock mass discontinuities in geological formations

Uplift failure and stability analysis of high-pressure gas storage tunnel in Hoek-Brown rock mass

Dynamic classification method for TBM cutting face rock mass boreability based on tunneling characteristics and multi-criteria decision analysis

FDEM modeling of the fracture, fragmentation and collapse process of rock masses with pre-existing joints by smooth blasting during deep tunnelling

An interpretable rock mass quality intelligent classification model (IRICM) driven by refined decision rule and its application

Deterioration and damage characteristics of rock masses within the fluctuating zone, Three Gorges Reservoir Area, China

Semi-analytical solution for bidirectional strain-softening behavior of surrounding rock mass in compressed air energy storage caverns

Mechanical characteristics and brittleness evaluation of rough-jointed rock masses under uniaxial compression

Visco-elastic interface and dynamic response of a lined tunnel in anisotropic rock mass under unloading waves

Experimental study on macro-meso damage of jointed rock mass under sequential cyclic loading–unloading followed by freeze–thaw cycles

Data-driven constitutive modeling of rock mass: Internal variables and finite element simulation

Applications and advances in characterizing pore-interface structures in coal using small angle scattering technology: A review.