Publications

The mechanical performance of cemented paste backfill (CPB) can be enhanced by incorporating very low amounts of nano-fibrillated Cellulose (NFC), a novel and sustainable biomaterial derived from wood pulp. This study demonstrates that even a minimal addition of 0.1 wt% NFC significantly accelerates the strength development in CPB, while simultaneously enhancing the ultimate strength of the cured material. In a CPB system containing 5% cement, the addition of 0.1% NFC resulted in nearly doubling of the 7 day compressive strength. This achievement led to a 7 day compressive strength in the NFC-supplemented sample equivalent to the 14 day compressive strength of the control sample. These results indicate that low addition levels of NFC have the potential to significantly reduce the required cement content to achieve desired mechanical performance. Furthermore, it is hypothesized that incorporating NFC into the plug can play a pivotal role in continuous fill operations, where high yield stress and rapid curing of the plug are advantageous. Additionally, NFC could be used to reduce the overall cement content and therefore contribute to a reduced carbon footprint in CPB.

Dewatered tailings can be among the most difficult flowing bulks solids found in the mining industry. Understanding the scientific principles that guide good bin and feeder design for difficult flowing cohesive materials, such as dewatered tailings, is key to knowing how to design an appropriate storage and feed system capable of reliably handling these materials. In the late 1970s, Kamengo launched a 15 yr research programme to understand and resolve the root causes of bin plugging, including for handling difficult flowing cohesive bulk solids such as dewatered tailings. The research showed that good bin design centres on choosing the correct geometry for the storage bin using the flow properties of the stored material. The standard for a correctly designed storage bin is that with the feeder removed, it should selfempty with only the aid of gravity. The research also showed that the feeder can be a significant culprit in creating plugging problems in a storage bin, including storage bins with correct geometry.

First, conventional feeders have a tendency to compact the stored material. With many cohesive bulk solids, when they are compacted, they gain strength very quickly. The more shear strength a bulk solid has, the wider the opening over which it can bridge. When compacted enough, a cohesive bulk solid will develop the strength to bridge over the feeder. Second, conventional feeders have a tendency to withdraw material selectively from the storage bin’s discharge outlet. Uneven discharge promotes a first-in, last-out discharge pattern. This is problematic because most cohesive bulk solids, including dewatered tailings, will not reliably discharge in a first-in, last-out discharge pattern.

In summary, the research demonstrated that a reliable storage and feed system handling cohesive bulk solids requires both: a) a storage bin with correct bin geometry; and, b) a feeder that withdraws material evenly from the entire discharge opening of the storage bin.

The mining industry faces evolving challenges in adapting to the impacts of climate change. Among these challenges is the management of tailings. Traditional methods of tailings disposal, primarily utilizing water-based tailings dams, are increasingly vulnerable to the shifting climate patterns, making alternative approaches imperative. This study focuses on investigating surface disposal of frozen non-cemented paste tailings, particularly the effect of water content (ie, 20 and 30%) and ambient temperature (ie, -5 and -15 °C) on the mechanical characteristics and the thermophysical properties of the frozen paste tailings. Results of thermophysical properties suggested an enhanced conduction medium for paste tailings compared with dry porous tailings. Unconfined compression strength (UCS) test results deemed the effect of the ambient temperature to be the most dominant, despite having additional influence from water content. The highest UCS observed is 0.62 MPa for a sample with 30% water content, tested at -15 °C. The lowest UCS observed is 0.26 MPa for a sample with 20% water content, tested at -5 °C. This study suggests further investigation to the characteristics and variables that are important in cold regions, such as freeze-thaw cycles and thermal behavior at sub-zero temperatures.

Cemented paste backfill has become the standard in modern cut-and-fill and long-hole stoping mines globally. It has proven to be an efficient method in maximizing ore recovery while reusing up to 50% of the tailings for underground stope fill. To reach the required fill strength, paste backfill must incorporate a cementitious binder. The cost of this binder can account for up to 75–80% of the total backfilling cost. Therefore, reducing the binder content can generate substantial savings while reducing cement related CO2 emissions. The loss in strength due to binder reduction can be compensated by paste backfill admixtures, which allow an increase in the paste solid content while maintaining a flowable paste. This study analyses cemented paste backfill mixes sourced from three different Canadian hard rock mines. Laboratory results validate significant binder reduction by changing the paste mix designs. The use of customized cementreducing admixtures results in a paste solid content increase, ranging from 3–4%, which in turn, facilitates a total binder reduction of 14–26%. This binder reduction translates to a reduction in CO2 eq/kg of paste, ranging from 4–26%.

During the process of extracting minerals through underground mining methods, voids are created. These voids need to be filled to prevent the sinking of the ground and reduce problems that may occur after the mining activity. Traditionally, sand has been the primary material used for backfilling. However, due to the growing demand in the construction sector and the slow rate of replenishment, there has been a search for alternative backfill materials. Several researchers have suggested using fly ash as a replacement for sand. However, due to its slow settling rate and the creation of hydrostatic pressure, use of fly ash necessitates appropriate techniques be employed. This study involved combining fly ash (FA) and high-density polyethylene (HDPE) plastic in a ratio of 80:20 to create a synthetic lightweight aggregate. The investigation sought to evaluate its appropriateness as a hydraulic backfill material. The results exhibit an exceptionally high slake durability index, a low specific gravity that enables easy transportation of the material at low pressure, an enhanced grain size distribution, a sand-like morphology, and a permeability 25 times higher than that of pure fly ash. These findings indicate that the combined aggregates show potential as a hydraulic backfill material.

Paste backfill or pastefill, has become the industry standard for sustainable mine fill; minimizing surface tailings storage requirements, while maximizing resource recovery underground through improved local and regional stability. To realize all the benefits of paste backfill, a ‘good’ product must be produced, meeting all specified uncured and cured material properties including ingredient quantities, rheology, early strength, and final strength. When these specified properties are not met, the impact on safety, the environment, and mining production can be catastrophic.

While the immediate short-term consequences (blocked lines, paste spills, etc.) of bad paste are well known, the long-term downstream consequences and related costs are rarely totaled and reflected upon, as mine planning and operations adjust in haste after which the mining cycle continues. These long-term consequences include:
• re-working mine designs
• additional underground development requirements
• mass failure into adjacent stopes
• significant paste dilution affecting skip production and mill performance • delay of sequences, and • sterilization of ore.

Resulting costs stemming from bad paste are typically absorbed by multiple departments, such as engineering, mine haulage/development, mine backfill, and the processing plant. As such, the costs are rarely totalled and attributed to the bad paste incident.
The cost of the downstream flow-on effects that can be attributed to the original bad paste events have been examined. The quantification of these costs will help operations justify the upfront costs of good quality backfill engineering, construction, instrumentation, engineers, and operators that are often overlooked in attempts to reduce capital and operational expenditures.

With the gradual depletion of surface and shallow mineral resources, deep mining has become the trend of future mining development. In the process of deep mining, the temperature will increase with the increase of mining depth, and will have a significant impact on the hydration reaction rate and products of the backfill; this changes the physical and mechanical properties of the backfill and affects backfill stability in the underground stope. In this study, the unclassified tailings of a gold mine and ordinary Portland cement were used as filling materials. By means of nuclear magnetic resonance (NMR) analysis, scanning electron microscope (SEM) observation, and a uniaxial compression experiment and theoretical analysis, the characteristics in the early curing stage of the unclassified tailings backfill slurry under high temperature conditions and the evolution strength rules of the backfill were explored. The results show that an increase of temperature leads to decrease of porosity in backfill slurry, decrease of free water content, and an increase of adsorbed water and pore water content. Increasing the curing temperature can increase the degree of hydration reaction such that the hydration products of the backfill form a denser structure; this eventually leads to the increase of the strength of the backfill. These research results have important theoretical significance for the strength design of backfill in deep mining.

'Tight' backfilling of stopes can be required for geotechnical reasons, and 'blind' filling can be required for logistical placement reasons, potentially resulting in an overall tight-filled condition. Such practices present elevated levels of risk for containment barricade failure in comparison to standard (ie, non-tight) backfilling. Barricade failures can result in high-energy release of backfill into underground workings posing significant hazards where risks are not mitigated. Challenges relating to tight-filling deserve more scrutiny as, to our knowledge, this practice has resulted in most of the barricade failures during the past decade. Increasing awareness of a specific risk is a critical (and potentially overlooked) tool in improving industry safety. In 2007, researchers documented several barricade failures and provided valuable contributions to increasing safety and best practice awareness. Here, this record is updated with the inclusion of seven tight-fill related barricade failures that have occurred at well-respected mines within North America and Australia since 2017.
While the causes of failures are varied, the common trend is that tight backfilling induced elevated pressures within backfilling stopes which have exploited weakness in barricade construction or simply caused apparently sound barricades to fail. Best practices resulting from lessons learned include maintaining adequate ventilation in terms of positioning, size, and construction of breather pipes in stopes and 'spill holes' in barricades, and in tracking and reconciling as-placed fill volumes versus predicted volumes. The use of on-barricade pressure instrumentation may provide useful information. Further, there is opportunity for novel instrumentation approaches to mitigate human error in the potentially unreliable practice of observing continued air flow via breather hole 'flags'. Tight-filling poses a potentially inherent risk of elevated barricade pressures; thus, mitigation factors such as limiting 'fluid' portions of fill, and providing and enforcing conservatively designed exclusion zones are operational requirements.

Traditional manual approaches to managing backfill systems are being replaced with improved and more efficient methods that are faster and safer. Automated diverter valves are among the technologies being used to effect efficiency and safety gains. Using diverter valves eliminates time-consuming manual operations that require special equipment and put workers in harm’s way. A case study that assesses automated diverter valve operation and manual diversion at an Australian mine provides a comparison of functionality, time-savings, and safety advantages inherent to the diverter valve.

The liquefaction potential of cemented paste backfill (CPB) masses under cyclic loading at early ages is a concern in underground mine backfilling operations. As underground mines face gradual depletion of shallow ore reserves in various regions worldwide, mining operations are increasingly moving to greater depths with larger volumes, leading to more severe and frequent cyclic loading events. This research utilizes the shaking table technique to assess the liquefaction potential of hydrating CPB during cyclic loading at early ages. A series of shaking table tests were conducted on large, fresh CPB samples cast in a specially designed flexible laminar shear box. Some of these tests were carried out at different curing ages (2.5, 4.0, and 10.0 hrs) to investigate the influence of cement hydration progress on CPB's liquefaction potential.

Additionally, another set of tests explored the impact of pore-water or mixing water chemistry, specifically sulphate content, on the seismic response of fresh CPB by subjecting CPB models to seismic loads with varying sulphate ion concentrations. Various parameters, such as pore water pressure, horizontal and vertical displacement, acceleration, temperature, and electrical conductivity, were continuously monitored before, during, and after shaking. The results revealed distinct cyclic behavior and performance of CPB under different conditions. Specifically, the progress of cement hydration (longer curing time) enhanced the liquefaction resistance of CPB, while the presence of sulphate ions diminished it. Furthermore, the study demonstrated that the acceleration, horizontal and vertical displacement, and excess pore water pressure of CPB under cyclic loading were greatly influenced by the curing time, depth within the CPB, and the chemistry of the mixing water.

These findings contribute to a deeper understanding of the cyclic behavior and liquefaction potential of CPB at early ages, providing valuable insights for liquefaction assessment of CPB structures.

In the Abitibi-Témiscamingue mining region, underground mining operations extensively employ cemented paste backfill (CPB) as a crucial secondary support method in stopes following ore extraction. This method has become indispensable and widely adopted. However, its utilization of binders encompassing basically Portland cements and blast furnace slag contribute to elevated costs and an increased carbon footprint. These challenges are further exacerbated by the logistical complexities of transporting binders to remote mining sites. Consequently, there is a pressing need to explore alternative, cost-effective, and environmentally friendly binders that leverage locally available manufacturing materials.

This study explores the potential application of limestone calcined clay cement (LC3) in CPB using the calcined Abitibi clays. The Abitibi-Témiscamingue region in Canada is endowed with extensive clay reserves, presenting a valuable source to produce supplementary cementitious material (SCM). A recent preliminary investigation study has been conducted to assess the viability of utilizing a specific clay from Rouyn-Noranda city in Abitibi-Témiscamingue region as a precursor of SCM. The clay sample underwent calcination within the temperature range of 700–850°C for LC3 production. Numerous CPB specimens were manufactured using this new type of LC3, as well as the conventional LC3 based on metakaolin. Subsequently, these specimens underwent uniaxial compression tests to determine the unconfined compressive strength (UCS) after curing periods of 7 and 28 days. The results reveal comparable UCS values at 28 days between the new type of LC3 and the conventional LC3 incorporating metakaolin.

The obtained results show promising UCS at 28 days. However, additional samples are imperative to ascertain the quality of clays in Abitibi-Témiscamingue region and their suitability for incorporation into LC3 cements for CPB. The effectiveness of these binders is anticipated to yield significant economic and environmental benefits for the Abitibi-Témiscamingue mining region. Furthermore, this project promotes the local supply of cements with a minimized carbon footprint.

Pastefill is used as an efficient, sustainable product to improve safety and stability of underground mines, while facilitating continued extraction of ore. Many mines have the advantage of using fresh tailings derived from the process plant to produce pastefill; however, this is not always possible if the mine and processing facility are not co-located, tailings quantities are insufficient, or the properties of the tailings are not suitable to make pastefill. Mines subject to these conditions are then required to look at alternative sources to procure pastefill, such as excavation of nearby tailings from historic mining operations.
This paper examines use of tailings from a historic gold mining tailings storage facility as pastefill for Kidd Mine. With the mine considering further expansion and deepening, the existing tailings source and two alternatives were critically assessed to determine a suitable source for continued pastefill production. Test work was completed and a thorough review of the tailings properties and their influence on pastefill strength and rheology was completed. The test work also reviewed the impact of temperature on the pastefill strength given the expected temperatures of the mine at depth. Further to the physical, mechanical, and metallurgical properties of the tailings sources, the economic implications and practical challenges associated with excavating tailings from each of the sites was evaluated to determine a suitable source to align with the potential mine expansion.

Mine tailings are filtered and stored on the surface in tailings storage facilities to create self-supporting tailings. However, tailings containing phyllosilicates (such as muscovite-fine tailings) may be susceptible to long-term freeze-thaw and wet-dry cycles. These environmental conditions can adversely affect hydrogeochemical stability, including the modification of saturated hydraulic conductivity (ksat), water retention curve (CRE), and mobility of chemical elements, especially in the case of sulfide deposits. Additionally, these conditions impact the physical stability, including mechanical strength and bearing capacity of these tailings.

To mitigate these potential impacts, the use of hydraulic binders to solidify and stabilize these tailings is becoming increasingly a necessity. In these tests, small quantities of HE cements (0.5, 1.5, and 2%) were added to the filtered tailings, incorporating different proportions of muscovite (9.5, 12.5, and 15.5%) to form mix recipes. These blends were subjected to several tests after 28 days of curing at a controlled temperature of 18°C. Test results showed significant improvements in uniaxial compressive strength (UCS), ksatt, pH, Eh, and electrical conductivity (EC); all parameters improved with the addition of 2% HE cements to muscovite-bearing mine tailings of up to 15%. UCS increased from 61 kPa for unamended tailings to 493 kPa for tailings amended with 2% HE cements, ksat decreased from 10-7 m/s to 10-9 m/s, and pH increased from 7 to 8.6.

The results of this study highlight the positive impact of incorporating cementitious amendment to phyllosilicate-bearing mine tailings stored on the surface under northern conditions. This finding presents an opportunity for mining companies to establish a more responsible, safe, and sustainable management system for the mining environment, all at a lower cost.

The decline in strength of cemented paste backfill (CPB) presents a recurrent challenge in underground backfilling operations. The heightened presence of phyllosilicates in CPB is recognized as a key factor contributing to its strength degradation. While some studies in civil engineering have delved into similar phenomenon, noting a decrease in concrete strength with rising mica content, there is conspicuous gap in research addressing this specific phenomenon within CPB.

This study systematically investigates the mechanical and hydrogeochemical responses of CPB influenced by phyllosilicates, specifically muscovite, addressing both quantitative and qualitative dimensions. The primary objective is to scrutinize the influence of varying muscovite contents on the hydration characteristics of the binding agent within CPB. The experimental program is meticulously designed to unveil significant changes in CPB physicochemical and mechanical properties across diverse muscovite contents (0%, 3%, 12% and 18%) throughout varying curing times (7 , 28, and 91 days). This investigation employs one binder type, general use Portland cement (Type GU) at two binder contents (Bw, 5 and 7%).

The findings from this study provide fresh perspectives on how phyllosilicates, particularly muscovite, impact the mechanical and physicochemical properties of CPB during both mixing and hardening phases. These insights contribute valuable knowledge for refining new CPB formulations (mix recipes) by thoughtfully considering the phyllosilicates content in mine tailings.

Artificial intelligence (AI) stands as one of the most remarkable advancements in human history, finding applications across various sectors such as industry, healthcare, law enforcement, and finance. Despite its widespread integration, the mining industry, from exploration to exploitation, has been slow in fully utilizing the potential of AI. This is particularly evident in areas such as monitoring underground operations and detecting anomalies like seismic events and faults in mechanical systems. As the use backfill materials becomes crucial for mineral extraction, ongoing research challenges arise in comprehending and studying the diverse properties (mechanical, rheological, physical) of these materials. Cemented paste backfill (CPB) is the prevailing choice for mine backfill, with unconfined compressive strength (UCS) being a critical property defining its mechanical behavior. However, predicting the UCS of CPB remains a formidable challenge.

Exploiting the extensive big data generated by the mining industry provides an opportunity to create intelligent systems. This research aims to develop a smart tool utilizing Machine Learning (ML) and Deep Learning (DL) to predict the UCS of cemented paste backfills. To achieve this, a comprehensive dataset was compiled from Agnico-Eagle mines and supplemented with laboratory data, resulting in a rich database (DB) of 10,050 CPB specimens that encompass the physical, chemical, and mineralogical properties of ingredients. Prior to model training, an exploratory data analysis was conducted. Various intelligent models, including Random Forest (RF), Gradient Boosting Regressor (GBR), eXtreme Gradient Boosting Regressor (XGBR), and the Deep Neural Network (DNN), were employed. Based on performance indicators, the top-performing models, GBR and DNN, demonstrated coefficients of correlation (R) equal to 0.970 and 0.969, respectively. These models underwent validation in the laboratory through the preparation of new CPB mixtures. To make these models applicable for the mining industry, a user-friendly web application was developed, ensuring accessibility and ease of use for industry professionals.

To tackle the issues associated with mine waste management, adopting a sustainable strategy involves repurposing solid waste into raw materials. This practice contributes to the development of conventional mine backfills, notably cemented rockfills (CRFs). CRFs are widely employed in the mining sector due to their capacity to deliver high unconfined compressive strength (UCS) and ensure effective ground stability and control. Despite their prevalence, the intricate preparation procedures, and diverse composition of CRFs have hindered their broad acceptance. Moreover, the lack of a systematic design to facilitate binder usage control for CRFs further exacerbates this challenge in the mining industry.

The objective of this study is to develop a thorough technical quality control procedure for CRF mixtures, with a specific focus on predicting their compressive strength. The methodology encompasses the initial empirical validation and calibration of an existing semi-empirical model, utilizing laboratory-prepared mixtures with diverse formulations. Once successfully validated, the semi-empirical model is intended for broader application through the creation of a user-friendly application for predicting constants. Subsequently, a pragmatic quality control (QC) procedure of CRF will be implemented, integrating fundamental relations and gravimetric water content determination.

The outcomes illustrate the reliability of the semi-empirical model in predicting the UCS of CRF and cement slurry. This predictive capacity underwent assessment through linear regressions, revealing coefficients close to 1. An application has been devised to forecast parameters associated with the type of cement used in CRF mixtures, streamlining the prediction of suitable values based on experiment-related data. Furthermore, the results emphasize the importance of vigilant monitoring of geotechnical parameters (final wet density, dry density, gravimetric water content) and a meticulous selection of components for cemented rockfill mixtures to uphold their stability.

Underground backfilling allows for the effective disposal of mine waste; however, the backfill must also be able to withstand a certain load, as in most cases it is used as an underground construction material such as in cut-and-fill mining methods. Therefore, the composition of the mill tailings utilized in the backfill must be such that when combined with a binding agent and pumped underground, the slurry or paste is then able to withstand a certain load within a specified period of time. High-pyrrhotite content tailings are commonly found on mine sites throughout Ontario and Quebec. These high-pyrrhotite tailings are reactive and can easily oxidize, producing acidity and/or metal-laden drainage under certain disposal conditions. This means that the pyrrhotite in the tailings can result in acid mine drainage if stored on surface, but can also cause strength degradation if used in excessive concentrations in underground mine backfill. Bioleaching processes can be used in an attempt to neutralize the tailings, reducing the resultant strength degradation. These bioleaching processes can provide an additional benefit by transforming mine waste from an environmental hazard to an economic opportunity, as the tailings may contain significant metal values.

CanmetMINING has developed a novel stirred-tank bioleaching process for recovering nickel and cobalt (both critical for vehicle electrification) that incorporates both partial neutralization and iron removal in the bioleaching circuit; bench-scale tests have resulted in excellent nickel and cobalt recovery over a range of temperatures. The resulting process residue contains a significant proportion of jarosite, which can be problematic for long-term disposal. This paper reports on research designed to evaluate different options for disposal of the high-jarosite residue into a suitable underground mine backfill material.

Historically the limit equilibrium solutions by Mitchell and Roettger (1989) have been used when specifying backfill strengths for horizontal exposures. While these solutions have proven useful for small spans, where ground support is included (eg, in underhand cut and fill mining), experience shows this approach to underestimate dilution in larger underhand stoping applications with cemented paste and hydraulic fill, and overestimate the strength required to prevent catastrophic failure (ie, achieve stability, while permitting some dilution).

Persistent, cohesionless, horizontal ‘cold/flow’ joints, which form during the hydraulic deposition process are expected to be controlling the horizontal exposure mechanism. After incorporating the influence of these joints into discontinuum numerical analysis, this model is shown to provide a more reasonable representation of the relationship between dilution and strength during horizontal exposures. Based on the mechanics revealed from the numerical output two new analytical modes are proposed for representing the horizontal exposure behaviour. The first is based on Voussoir beam theory and relates depth of overbreak (or dilution) to backfill strength, while the second provides a model for estimating the strength below which catastrophic, uncontrolled caving would occur. Finally, the analytical solutions suggest horizontal exposures to be largely independent of tensile strength. This is verified through a numerical sensitivity study.

The increasing depth of underground mines, driven by the scarcity of surface ore deposits, has led to higher horizontal ground stresses and subsequent rockwall closure, impacting underground mining operations. Cemented paste backfill (CPB) is commonly used to support excavations, but its response to multiaxial stress conditions in deep mines remains poorly understood. This research addresses this knowledge gap by introducing a new multiaxial compressive stress (MCS) curing and monitoring apparatus for CPB capable of simulating rockwall closure-induced stresses encountered in underground mines. The developed apparatus applies two horizontal stresses (σH1 and σH2) resulting from rockwall closure and a vertical stress (σV) to CPB samples during curing. Validation tests confirm its efficacy and reliability to replicate rockwall closure conditions. Employing this apparatus, the study investigates how rockwall closure impact strength development of the studied CPBs.

Experimental results indicate that time-dependent multiaxial compressive stresses, including vertical stress from self-weight and rockwall closure-induced horizontal stresses, can significantly enhance the early-age unconfined compressive strength (UCS) of CPB. Specifically, the UCS improvement at curing ages of 1, 3, and 7 days amounts to 29, 58, and 37%, respectively, compared to control samples without multiaxial loadings. This strength enhancement is attributed to the densification of the CPB's pore structure and the acceleration of cement hydration. It is crucial to note that rapidly increasing rockwall closure-induced horizontal stresses at later curing ages have notable contribution to further densification of CPB. Moreover, the study identifies that the horizontal and vertical deformations within CPB are significantly influenced by stress evolution in each axial direction. These findings provide valuable insights into the curing behavior of CPB under rockwall closure-induced stresses, facilitating an improved understanding of CPB performance in deep mining applications. This knowledge is crucial for optimizing backfilling practices, enhancing underground mine safety, and ultimately increasing mining efficiency in deeper ore deposits.

The quality of cemented backfill mass is of great importance for utilizing mining with backfill method, thus the quality evaluation of backfill mass has long been the research focus for researchers and engineers of mining. Generally, the evaluation can be analyzed based on the strength value fluctuation of the samples drilled from in situ backfill, which can demonstrate the peak strength value or the position of weak quality areas, while the essential causes leading to the changes and distribution cannot be acquired. Therefore, in this study the quality evaluation method based on segregation degree analysis, which mainly utilizes the measurement results of cemented contents and porous properties of samples, has been described. Based on this method, the strength distributions and segregation indexes of cemented backfill samples of a real mine have been analyzed, and the following results have been determined:

1. The cement content increases gradually along the drilling hole, while the porosity has a fluctuating trend, which are all different from the strength distribution.
2. The strength of the sample is not just determined by cement content but also is coupled and affected by porous properties.
3. By analyzing the segregation properties of drilled samples, some optimization suggestions about the particle size distribution of backfill materials can be gained.