Salt Mine Research Articles

Feasibility assessment of solution mining and gas storage in salt caverns: a case study of the Sanshui salt mine

The Sanshui salt mine is the sole location in the Guangdong province of South China with the potential to construct a salt cavern gas storage (SCGS) facility. Nevertheless, the gas storage construction of this mine faces significant challenges due to the presence of low‒grade salt deposits and numerous interlayers. To demonstrate the feasibility and calculate the gas storage capacity in this specific mining area, two representative salt caverns within this salt mine were simulated using a self-developed cavern-building simulation program, enabling us to accurately determine their respective volumes and shapes. Herein, the findings indicate that the combined caverns possess a total mining space volume of 1,157,000 m3, with the brine space accounting for merely 291,800 m3 (representing 25.22% of the overall mining space), and an extensive sedimentary volume of 865,200 m3 is also observed (constituting approximately 74.78% of the total mining capacity). Fortunately, this study has revealed that the sediments exhibit a porosity exceeding 40% and possess favorable permeability; consequently, countermeasures have been proposed to enhance the gas storage capacity within the pore space of these caverns, and we also utilized FLAC3D software for numerical simulation calculations to compare the stability of the cavern under different conditions of sediment pore utilization by calculating the volume loss rate, cavern wall displacement deformation, and plastic zone distribution. Moreover, the proposed method is anticipated to double the caverns’ working gas volume, increasing it from 40 million m3 to nearly 80 million m3. On the other hand, the long-term stability of caverns is numerically assessed under different pore space utilization rates of the sediments. The results also indicate that the caverns’ volume shrinkage, plastic zones, and surrounding rock displacement remain within allowable limits during 30 years of gas storage operation. The primary problem in the subsequent phase lies in effectively achieving gas injection and brine removal from the pore space of sediments while devising a methodology to extend this method to other salt caverns within similar salt mine areas. Thus, this study provides theoretical and technical guidance for the establishment of gas storage in existing salt caverns in the Sanshui salt mine and in salt mines worldwide that share similar geological conditions.

Disposal of drilling waste in salt mines in China

A lot of drilling wastes are produced during oil/gas exploration and exploitation in China. Many countries have built and successfully run projects to dispose of wastes in salt mines, which fully demonstrates the feasibility and superiority of this technology. The application prospects of using salt mines to dispose of drilling wastes is comprehensively evaluated from many aspects. It is concluded that this technology has broad application prospects in China. The scientific and technical problems that need to be solved in order to successfully use this technology are systematically summarized, and some practical suggestions are put forward to improve relevant laws and policies. Considering the geological conditions of salt mines and the requirements of laws and regulations in China, a set of perfect and more advanced Chinese schemes has been proposed.

The discovery of the first potash mine and the development of the potash industry since 1861

AbstractThe birth of potash industry was 1861 in Staßfurt, Duchy of Prussia with commissioning of the first potash plant. During the mining of rock salt in Staßfurt, seams containing potassium had previously only been discovered by chance and initially treated as overburden. Until 1918, potash production was only in the German Empire with a total capacity of about 0.83 million t K. Subsequently, a successful global exploration for further potash deposits began. Large and high‐quality potash deposits are found in the Northern Hemisphere in Europe, Canada, Russia, and Belarus. From around 1950 onward, the industry began to grow strongly. In 2021, the global production was about 36 million t K. More than 90% is marketed as fertilizer, mainly potassium chloride. Feeding the world's growing population requires a safe and adequate supply of fertilizer. The potash production capacities are correspondingly high and the global supply of potassium fertilizer is secured for centuries to come.

Stress drop variations of the 2019 ML 6.0 Changning earthquake and its aftershock sequence in the southern Sichuan Basin, China

The Lg-wave spectra are investigated for the 2019 Changning ML 6.0 earthquake and its 94 aftershocks with magnitudes above ML 2.8, which occurred in the southern Sichuan Basin, Southwest China. This earthquake sequence is potentially related to the water injection from nearby salt mining activities. Based on an established regional high-resolution broadband Lg-wave attenuation model, we correct the observed spectra for the attenuation effect along the propagation path. By fitting the observed spectra from the Changning earthquake sequence with the theoretical source model, we estimate seismic moments and corner frequencies, from which the stress drops are calculated for the entire earthquake sequence. The results show that the stress drops are rather scattered, ranging from 0.16 MPa to 32 MPa with a median value of 0.78 MPa. Spatiotemporal variation of stress drops reflects strong fault heterogeneity and a complex stress release process, which is likely influenced by water injection and diffusion. Positive trends are observed between the stress drop and focal depth and between the stress drop and seismic magnitude. Relatively lower stress drops for most shallow events are possibly the indication of lowered normal stress by long-term fluid injection. No apparent relation is observed between the stress drop and the distance to the Shuanghe salt mine, where water was injected. Combining the actual water injection data and previous numerical simulation studies, we suggest that the salt mining-related water injection may lead to elevated pore pressure beyond the source region of the 2019 Changning earthquake. The increasingly cumulated underground water may have created pathways linking multiple fault systems, thus the possibility of future large induced-earthquakes cannot be ruled out.

Feasibility analysis on the utilization of TWH-caverns with sediment space for gas storage: A case study of Sanshui salt mine

Underground salt cavern (USC) has emerged as an optimal location for large-scale energy storage, encompassing oil, gas, hydrogen, carbon dioxide, and compressed air energy storage (CAES), owing to its inherent advantages of substantial capacity, stability, and hermeticity. However, most salt mines in China are characterized by a relatively thin salt layer thickness, a large number of interlayers and low salt layers grade. Consequently, a substantial proportion of the cavernous space resulting from water solution mining becomes progressively covered by insoluble sediment. Herein, the feasibility of gas storage in two butted-well horizontal (TWH) caverns with sediments, located within the Sanshui salt mine in Guangdong Province, China, is comprehensively analyzed through engineering investigation, physical model experimentation, numerical simulation, and theoretical analysis. Firstly, a theoretical model was developed to calculate the volume of caverns based on salt grade (soluble content). Secondly, a joint physical model experiment and numerical simulation were conducted to obtain the most probable shape of the process for forming water-soluble caverns. Moreover, a novel technology was proposed to utilize sediment space for gas storage in TWH-caverns. Ultimately, the support pressure of surrounding rock was determined by using the passive earth pressure theory, and subsequently, an assessment of cavern stability was conducted. Here, the numerical simulation results demonstrated that in the absence of sediment space utilization, there was a limited capacity for gas storage, resulting in significant deformation of the surrounding rock and an increased level of roof instability. On the contrary, sediment can provide structural support to the surrounding rock, thus increasing its stability (the plastic zone expansion was reduced from 1600 % (0.3 σz), 1345 % (0.35 σz) and 1297 % (0.4 σz) to 109 %, 87 % and 78 %, respectively) and enhancing the capacity for gas storage. Accordingly, this study provides valuable guidance for the assessment of gas storage in low-grade salt sedimentary environments, as well as for the design of gas injection and brine discharge, and stability evaluations.

Halobacillus trueperi CT7: A spore-forming, gelatinase producing, salt-tolerant bacteria isolated from Çankırı Salt Mine

Halophilic microorganisms are an extreme group of organisms that can spread at high salt concentrations, and a significant part of them consists of halophilic bacteria. Salt mines are important sources where halophilic bacteria are detected. In this study, Halobacillus trueperi CT7, a halophilic bacterium, was isolated from Çankırı Salt Mine. It was determined that this strain obtained showed 98.16 % similarity to Halobacillus trueperi by DNA isolation and sequence analysis as well as biochemical analysis. In addition, two-dimensional (scanning electron microscopy) and three-dimensional (atomic force microscopy) images of Halobacillus trueperi were performed. In order to determine the industrial use potential of the microorganism, the minimum and maximum salt concentrations, temperature and pH ranges, as well as the enzyme activities, where the species can grow, were determined qualitatively. The interest in halophilic organisms for their use in extreme industrial processes is increasing day by day. It is thought that this study will contribute to future studies on halophilic bacteria.

Dynamics of Methane-Consuming Biomes from Wieliczka Formation: Environmental and Enrichment Studies.

The rocks surrounding Wieliczka salt deposits are an extreme, deep subsurface ecosystem that as we studied previously harbors many microorganisms, including methanotrophs. In the presented research bacterial community structure of the Wieliczka Salt Mine was determined as well as the methanotrophic activity of the natural microbiome. Finally, an enrichment culture of methane-consuming methanotrophs was obtained. The research material used in this study consisted of rocks surrounding salt deposits in the Wieliczka Salt Mine. DNA was extracted directly from the pristine rock material, as well as from rocks incubated in an atmosphere containing methane and mineral medium, and from a methanotrophic enrichment culture from this ecosystem. As a result, the study describes the composition of the microbiome in the rocks surrounding the salt deposits, while also explaining how biodiversity changes during the enrichment culture of the methanotrophic bacterial community. The contribution of methanotrophic bacteria ranged from 2.614% in the environmental sample to 64.696% in the bacterial culture. The methanotrophic enrichment culture was predominantly composed of methanotrophs from the genera Methylomonas (48.848%) and Methylomicrobium (15.636%) with methane oxidation rates from 3.353 ± 0.105 to 4.200 ± 0.505 µmol CH4 mL-1 day-1.

Improved imaging of ground deformation and brine seepage around abandoned flooded salt mines by joint inversion of multiphysics data

Centuries of bad mine-flooding practice have left a legacy of underground salt mine collapse and contaminated discharges, the scale of which is only slowly being revealed now that ground processes have caused instability over decades to >100 years. Geophysical methods are used for mapping ground subsidence and groundwater contamination at such sites but suffer individually from non-uniqueness and with the underlying mechanism and processes not being well understood. Here, to reduce uncertainty and maximize accuracy we recover subsurface models with structural similarity enforced via crossgradients joint inversion of seismic refraction and dc resistivity data for the top 40 m at former mining areas in Carrickfergus region of Northern Ireland. The models in combination with multispectral image fusion, enable us to identify hitherto unknown mechanism of deformation and compositional changes consistent with the Chebotarev geochemical evolution of groundwater. We found evidence of concealed gravitational slump structures interpreted as being caused by water ingress weakening the gypsum-bearing marl bedrock (via gypsum dissolution and increased fluid pressures within marl) and leading to gravitational gliding deformation, expressed as curved subsidence bands and stepped thrusts coincident with surface zones of brine-mud seepage and sinkhole collapse. Our results have wide-ranging implications for best-practice assessment and management of abandoned flooded salt mines and the hazards they pose to ground stability and water resources world-wide.

Seismogenic structures and earthquake mechanisms in the Changning area, China: Insights from seismicity and tomography

The Changning area, located in southwestern Sichuan Basin, China, was previously known to be a seismically inactive region. However, in recent years, the region has experienced an increase in the rate of seismic activity. To gain a better understanding of the seismogenic structures and earthquake mechanisms in the region, we deployed 298 short-period seismic stations and collected 47 days of continuous waveform data following the 2019 Ms 6.0 Changning earthquake. Using a machine-learning-based earthquake location workflow (LOC-FLOW; Zhang et al., 2022), we detected and located over 60,000 seismic events. These events were then used for three-dimensional Vp and Vs inversion using a double-difference tomography method (tomoDD). The results show that the earthquake distribution has distinct zoning characteristics with different mechanisms. In the Changning-Shuanghe anticline, most earthquakes are distributed in areas with large velocity and Vp/Vs gradients, typically occurring in regions with high velocity and low Vp/Vs, where tectonic stresses are prone to accumulate. Long-term water injections may promote fault activation in the southeast of Changning anticline. Earthquakes around the salt mining well were found to occur in sedimentary cover, indicating that the basement fault has not been activated but rather acts as a fluid-flowing path. In the Changning shale gas block, earthquakes showed different triggering mechanisms, accompanied by different velocity characteristics. The spatial variations in earthquake locations and velocity characteristics can be explained by the terrain at shallow depths, syncline structures, and the distribution of fluids and gas reservoirs. Our study provides new insights into the detailed seismogenic structures and earthquake mechanisms in the Changning area. These findings can be used to improve earthquake hazard assessment in the region.

Stability Evaluation of Horizontal Salt Caverns for Gas Storage in Two Mining Layers: A Case Study in China

To increase natural gas storage capacity and further utilize salt mine resources, salt cavern gas storage in the Yunying salt mine, Hubei Province, China, was simultaneously constructed in two different mining layers (K3 and K4). The purpose of this study was to investigate the long-term feasibility of operating salt caverns for gas storage in two mining layers. Based on the geological conditions and sonar test results, the geometric parameters for the salt caverns in the two mining layers were designed, and a 3D geomechanical model was built to predict the cavern stability. The corresponding evaluation index included the displacement, volume shrinkage rate, equivalent strain, and dilatancy factor. The results show that simultaneously operating salt cavern gas storage in two mining layers is feasible, and the operational pressures for the salt caverns in mining layers K3 and K4 should be no less than 4–9 and 7–12 MPa, respectively, to satisfy the stability requirements. The surrounding rock of the salt caverns presents a larger displacement and volume reduction compared with cases in which the salt caverns are operated in a single mining layer. Increasing the injection–withdrawal frequency increases the deformation of the surrounding rock.

Experimental assessment of the effect of different types of salt and temperature on the survival of the larval stage of eurasian perch Perca fluviatilis Linnaeus, 1758

Salinization of freshwaters is a serious problem leading to a decrease in biodiversity and degradation of aquatic ecosystems. In conditions of climate warming, the toxic effect of salinization can increase. The aim of this study was an experimental assessment of the survival of the pre-larvae of the Eurasian perch Perca fluviatilis under conditions of different concentration of two types of salt (salt mining wastes and sodium chloride), and also under two temperature regimes. We found that under temperature conditions of 8–15 ° C, the mortality of pre-larvae was significantly lower compared to the values obtained with an increase in temperature by 5 °C. The tolerance limit (LC50 ) under exposition to salts for 24 hours was a mineralization value equal to 9.8 g/l and 8.7 g/l under an exposition of 72 hours. There were no significant differences between the two types of salts — salt mining wastes and sodium chloride in terms of LC50. There were also no significant differences in the time of death of 100 and 50% of the tested prelarvae. At the same time, a higher mortality of pre-larvae was revealed in solution of salt-mining wastes at concentrations of 7 and 8 g/l. At concentrations above 9 g/l, the opposite trend was observed — a greater mortality rate was found in sodium chloride solution. For both types of salts, a greater survival rate of prelarvae was revealed at a salt concentration of 8 g/l compared to a concentration of 7 g/l, which requires more detailed studies. These results are important for understanding the limits of tolerance to salinity in the larval stage of development of one of the most widespread ecologically flexible freshwater fish species. The relevance of the study is determined by current trends in climate change and the increasing level of salinization of boreal freshwaters as a result of salt pollution.

Feasibility Analysis of Compressed Air Energy Storage in Salt Caverns in the Yunying Area

With the widespread recognition of underground salt cavern compressed air storage at home and abroad, how to choose and evaluate salt cavern resources has become a key issue in the construction of gas storage. This paper discussed the condition of building power plants, the collection of regional data and salt plant data, and the analysis of stability and tightness. Comprehensive analysis and evaluation methods were put forward from four aspects, including ground comprehensive conditions, regional geological conditions and formation lithology, salt mine characteristics, stability, and tightness of salt caverns. The limit equilibrium theory was applied to establish the limit equilibrium failure mode of salt caverns under operating pressure, and the stability coefficient calculation method of the target salt cavern was determined by combining the mechanical characteristics. Based on the physical and mechanical properties of salt rocks, it was found that salt rocks with enough thickness around the salt cavity could be used as sealing rings to ensure the tightness of the salt cavern. Combined with the field water sealing test, the tightness of the target salt cavern is verified. This method has been applied to the salt cavern screening and evaluation of a 300 MW compressed air energy storage power plant project in Yingcheng, Hubei Province, and remarkable results have been obtained, indicating the rationality of the method.

Using Group Decision-Making to assess the negative environmental, social and economic impacts of unstable rock salt mines in Maceio, Brazil

The disaster caused by the instability of rock salt mines in Maceió, Brazil, is the largest ongoing worldwide socio-environmental disaster in urban areas and has already affected approximately 60,000 families directly who needed to be relocated. To assess the negative impacts caused by this disaster, a Group Decision-Making (GDM) model was developed based on qualitative (Thematic Content Analysis) and quantitative (Nominal Group Technique) analysis. A comparative evaluation of the opinion of three groups of stakeholders was performed: two considered as experts, i.e., academic professors and local public agents, and a group of citizens directly affected by the disaster. As a result, the residents considered the relevance of the impacts in the three dimensions analyzed to be similar, while the experts gave greater importance to the social and economic dimensions than the environmental one. This study potentially contributes to society by guiding public policymakers in the decision-making process on mitigation and preventive actions, and academics interested in the governance of disasters caused by mining industries.

Cytotoxic effects of halophilic archaea metabolites on ovarian cancer cell lines

BackgroundOvarian cancer is one of the most frequent and deadly gynaecological cancers, often resistant to platinum-based chemotherapy, the current standard of care. Halophilic microorganisms have been shown to produce a large variety of metabolites, some of which show toxicity to various cancer cell lines. However, none have yet been shown to be active against ovarian cancer cells. Here, we examined the effects of metabolites secreted by the halophilic archaea Halorhabdus rudnickae and Natrinema salaciae on various cancer cell lines, including ovarian cancer cell lines.Results1H NMR analyses of Hrd. rudnickae and Nnm. salaciae culture supernatants contain a complex mixture of metabolites that differ between species, and even between two different strains of the same species, such as Hrd. rudnickae strains 64T and 66. By using the MTT and the xCELLigence RTCA assays, we found that the secreted metabolites of all three halophilic strains expressed cytotoxicity to the ovarian cancer cell lines, especially A2780, as well as its cisplatin-resistant derivative A2780cis, in a dose-dependent manner. The other tested cell lines A549, HepG2, SK-OV-3 and HeLa were only minimally, or not at all affected by the archaeal metabolites, and this was only seen with the MTT assay.ConclusionsThe halophilic archaea Hrd. rudnickae and Nnm. salaciae, isolated from a Polish salt mine and Lake Medee in the Mediterranean Sea, respectively, secrete metabolites that are active against ovarian cancer cells, including those that are resistant to cisplatin. This opens potential new possibilities for the treatment of these frequent and deadly gynaecological cancers.

Ebro Valley Gypsum Escarpment Near Zaragoza (NE Spain)—Combination of Highly Valuable Rock Record, Dynamic Geomorphosites and Associated Cultural Heritage

The 40-km-long escarpment of the Ebro River valley to the north-west of Zaragoza (NE Spain) is a remarkable geomorphological feature and an important geoheritage locality. Being 30 to 150 m high, the escarpment exposes a complex evaporate-clastic succession of Early to Middle Miocene age, with alternating gypsum and mudstone/marl units, as well as halite beds at depth. The escarpment is a highly dynamic feature, extensively shaped by mass movements of different types, especially in sections where it is directly undercut by the Ebro River. It also hosts abundant evidence of salt and gypsum dissolution, contributing to ongoing instability. Diverse cultural heritage is associated with the escarpment, including an ancient Celtiberian settlement, medieval castles, abandoned villages, rock-cut churches and dwellings and ancient salt mines. Twenty-six possible geosites are identified, with six considered as most representative described in detail. Opportunities to develop the area for geotourism are presented, but these will be associated with challenges of properly managing steep, dynamic and fragile terrain.

The Interaction Principle in the Assessment of Pillars’ Secondary Stress-Deformation State

Abstract In the field of mining, one of the exploitation methods that is still the most used in rock salt, potassium, and magnesium salt deposits is the method with the room and abandoned pillar. The salt mining method with rooms and pillars represents a unique spatial system for which the establishment of an optimal correlation between the parameters of the room, pillar, and rock massif is required in any given situation. Thus, the dimensioning of the most requested element in the system is followed, and depending on its parameters, the other parameters of the system are established. Considering the exploitation method with rooms and pillars, the pillars are certainly the elements that are subjected to the greatest loads. In the situation where the deep exploitation of salt is done with square pillars, the evaluation of the optimal parameters of the elements of the exploitation system requires: establishing the loads that appear in the surrounding salt massif (the natural stress state); the qualitative-quantitative determination of the way of distribution of the secondary stress state in the pillars; evaluating the bearing capacity of the pillars; and establishing their geometric elements. Solving this problem can be achieved by different methods: based on the theory of limit equilibrium, taking into account the effective stress in the pillars; methods of the mechanics of the continuous system based on the analytical models for evaluating the secondary stress and deformation state of pillars and floors; and numerical methods combined with the results and measurements from the laboratory and in situ tests. A methodology based on the pillar–room–salt massif interaction principle was proposed for the analytically achievable stability exploitation system of rock salt by the dry method as the depth increased. Applying this method, the secondary stress-deformation state in the pillar can be established by taking into account the rheological behaviour of the salt, changing the pillar shape, and the extraction technology. The presented algorithm can be extended in the field of exploitation, where the room and pillar exploitation methods are used.

A comprehensive feasibility evaluation of salt cavern oil energy storage system in China

Large-scale underground oil storage has a great effect on national energy safety. China's oil dependency has exceeded 70% for four consecutive years, so it is necessary for China to build strategic oil storage. The salt cavern is a good medium to store oil, and it is widely used in foreign countries. China is rich in salt mines and has basic conditions for building salt cavern oil storage (SCOS). In this paper, the necessity and advantages of SCOS are analyzed, the salt rock mechanics experiments of SCOS are conducted, the geological feasibility evaluation model is built, the 3D numerical creep stability model in three working conditions (long-term, oil pressure dynamic, injection and production) is built, and the economic feasibility evaluation model is built. The results show that the implementation of SCOS in China is feasible, the earthquake (51%) and fault (28%) have a great effect on geological selection, the SCOS has good stability under three working conditions, the storage cost of SCOS is lower by 64.3% and 84.3% contrasted to rock cavern and storage tank in 2025. The study has a reference value for the development of SCOS in China.

Usability of acrylates in damp proofing in deep-level salt mining

Usability of acrylates in damp proofing in deep-level salt mining

Radio Link Model for Node Deployment in Underground Mine Sensor Networks

This paper presents an experimental characterization of the proposed radio link model for an underground mine sensor network. Power efficiency and range are critical factors to consider when designing a wireless sensor network, particularly for low data rate applications where the goal is to have a long-lasting, low-maintenance network. A ‘deploy and forget’ strategy is desirable because it allows the network to operate autonomously without requiring frequent maintenance or intervention from network operators. DASH7 and IEEE 802.15.4f are both excellent choices for low-power, long-range wireless sensor networking applications. The proposed radio link model was developed and evaluated for 433 MHz DASH7 in underground mines, considering the practical electromagnetic properties of mine walls and the propagation medium, which helps in calculating accurate signal characteristics. Radio wave propagation is a critical factor that needs to be considered when designing a wireless sensor network for complex mine structures. The received signal strength indicator (RSSI) and packet error rate (PER) are two key parameters that are used to measure wave propagation and assess the quality of the radio link between sensor nodes. The radio link design has been optimized for complex mine structures by utilizing these parameters in a model, leading to improved performance and reliability. The measurements were carried out in the world’s second largest salt mine at Khewra, Pakistan, with representative irregular mine structures. The RSSI and PER were measured at different node positions and with variable separation between the nodes. The proposed model allows for the easy placement of nodes on either the rooftop or near the side walls of the mine corridors, with an average variation of 6% in RSSI and 1.9% in PER. The proposed model was validated using off-the-shelf wizzi sensor nodes received from Wizzi Lab, France, and was programmed to measure RSSI and PER while operating under the 433 MHz DASH7 protocol. An agreement between modeled and measured parameters has been noted, making the proposed model a decent method for efficient node deployment in underground mine sensor networks.

Respiratory Muscle Function in Older Adults with Chronic Respiratory Diseases after Pulmonary Rehabilitation in Subterranean Salt Chambers.

Training the respiratory muscles is a crucial aspect of pulmonary rehabilitation. The purpose of this study was to assess the function of respiratory muscles in older adults both before and after a period of pulmonary rehabilitation and treatment stay within the underground chambers of a salt mine. A total of 50 patients aged 65 years and older with chronic respiratory conditions was enrolled in the study. These participants underwent a 3-week subterranean pulmonary rehabilitation (PR) program in the "Wieliczka" Salt Mine. Levels of sniff nasal inspiratory pressure (SNIP), maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP) were measured using the MicroRPM both before and after the outpatient PR program conducted 135 m underground. A total of 44 patients with a mean age of 68.8 ± 2.9 years who completed the PR program and tests were included in the analysis. The average changes in the parameters of pulmonary function before and after the PR were: MIP 8.8 cmH2O, MEP 7.1 cmH2O, and SNIP 11.2 cmH2O (for p < 0.05). For patients older than 70 years, beneficial changes were only observed for MEP, which increased by 9.3 cmH2O (for p < 0.05). Speleotherapy combined with pulmonary rehabilitation improves respiratory muscle function in older adults with chronic respiratory diseases, mainly in terms of MEP. Therefore, a greater emphasis on inspiratory muscle training in the rehabilitation program should be considered.