Geotechnical Properties Of Rocks Research Articles

Review of Gully Erosion in Anambra State: Geology, Causes, Effects, Control Measures and Challenges Associated with Its Mitigation

In South-Eastern Nigeria, particularly in Anambra State, gully erosion presents a serious environmental challenge. With over 100 gully sites in the state, only about 30 have received measures of control but are still not fully under control. Observations have shown clearly that the underlying geology exerts major control over the development of gully erosion in the study area. Progressive gullies in certain areas of Anambra State are caused by various factors, including topography, soil and water pH, lithology type, deforestation, hydrogeology, and geotechnical rock properties. This erosion activity has resulted in the loss of productive lands, water pollution, sedimentation of waterways, and the loss of lives and properties almost every year. However, several government agencies have attempted to manage it using concrete structures, stabilization work such as planting bamboo and cashew trees to increase water intake, and pipe structures to channel the water directly to nearby surface waters through the construction of check dams, embankments, and retention ponds to control the flow of water and sediments. Despite these control efforts, several challenges persist in effectively managing gully erosion in Anambra State. Majority of the concrete structures used to control these gullies have collapsed, leading to the incessant spreading of the site. Inadequate funding, failure of engineering structures, flooding, the geologic setting of the area, limited technical expertise, population growth, urbanisation, a lack of public awareness, and a lack of proper coordination among stakeholders hinder the implementation of comprehensive erosion control measures. It is recommended that concrete drainage channels should not only be used in controlling these gullies but also be integrated with other measures to yield a positive result.

New Insights into the Internal Structures and Geotechnical Rock Properties of the Giant San Andrés Landslide, El Hierro Island, Spain

The San Andrés landslide on El Hierro (Canary Islands) represents a rare opportunity to study an incipient volcanic island flank collapse with an extensive onshore part. The presented research improves the knowledge of the internal structure and rock characteristics of a mega-landslide before its complete failure. The investigation combines multiple geophysical measurement techniques (active and passive seismic) and remotely sensed, high spatial resolution surveys (unmanned aerial vehicle) with in situ and laboratory geotechnical descriptions to characterize the rock properties inside and outside the San Andrés landslide. The available geophysical and geological data have been integrated into 3D geomodels to enhance their visual interpretation. The onshore geophysical investigations helped detect the possible San Andrés landslide sliding surfaces at depths between 320 m and 420 m, with a rather planar geometry. They also revealed that rocks inside and outside of the landslide had similar properties, which suggests that the previous fast movements of the landslide did not affect the bulk properties of the displaced rocks as the failure chiefly occurred along the weakened sliding plane. Uniaxial strength tests on basalt rocks further indicate a high variability and spatial heterogeneity of the rock strength properties due to the different types of volcanic rocks and their texture. The new information on the rock properties and structural setting of the San Andrés landslide can now be used to develop realistic geotechnical slope models of the onshore part of the flank collapse that are possibly applicable for slope stability or deformation calculations. It will also help assess related hazards marked by a low occurrence probability and a high impact potential.

Abrasivity evaluation for wear prediction of button drill bits using geotechnical rock properties

The current study investigates the wear life of button bits and rate of penetration (ROP) of rotary-percussive drilling machines by employing geotechnical rock properties. According to the research plan, three hydropower projects and six active mining quarries in Pakistan were included. The field work included recording of drill bit consumption (m/bit) and measurement of penetration rate (m/min) from the 11 selected rock units. A comprehensive laboratory testing plan on the collected rock units was carried out to include rock abrasivity assessment [CERCHAR (CAI), LCPC (ABR) and abrasion value steel (AVS) tests], NTNU/SINTEF drillability parameters [Sievers’ J-value (SJ), brittleness value (S20), Cutter Life Index™ (CLI) and Drilling Rate Index™ (DRI)] and physico-mechanical properties [uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), porosity (n), density (ρ), p wave velocity (Vp), Schmidt rebound hardness (SRH) and brittleness index (B3)]. Moreover, XRD analyses were performed to compute equivalent quartz content (EQC %), rock abrasivity index (RAI) and Vickers hardness number of rock (VHNR). The least square regression technique was employed to predict bit life from geotechnical rock properties. Dependence of ROP on geotechnical rock parameters was also discussed. Finally, two multiple linear regression models were also proposed for the estimation of bit life based on the included geotechnical rock properties. The developed multi-variable models were validated using the F-test statistical method. The correlations so developed are particularly proposed for rock engineers involved in rock drilling projects.

Water Saturation Influences on Engineering Properties of Selected Sedimentary Rocks of Pakistan

This study is focused on the evaluation of water saturation influence on the mechanical and physical properties of 34 sedimentary rock units selected from different geological formations in Pakistan. The laboratory testing program comprised the determination of physico-mechanical rock properties of both air-dry as well as fully water saturated rock specimens. Further thin section analyses of all rock samples were also performed to explain their petrography. According to the statistical analyses overall reductions of around 40 and 50% were found in UCSsat and BTSsat values, respectively, measured on saturated rock samples in comparison to their corresponding dry strength values, i.e. UCSdry and BTSdry. Linear correlations were found between ultrasonic wave velocities as well as density of both dry and saturated rock samples. In addition, the dry and saturated UCS values were exponentially related with the rock porosity. Multiple regression technique was also utilized to develop a predictive linear model of UCSsat with geotechnical rock properties in the dry condition and petrographical characteristics of rock samples. Finally the validity of multiple regression model developed in this study and an existing correlation for the conversion of UCSdry into UCSsat was statistically assessed.

Simulation of weathered profiles coupled with multivariate block-support simulation of the Puma nickel laterite deposit, Brazil

Modelling and assessing spatial variability and uncertainty of mineral deposits is critical for both capital investments in mining projects as well as operational issues once a mine is developed. However, traditional approaches for modelling geological domains and geostatistical estimation provide smoothed representations of the pertinent deposit attributes, ignore spatial variability and, thereby, can mislead downstream decisions. Spatial variability and related uncertainty in modelling mineral deposit characteristics of interest, ranging from metal content and geological boundaries to geomechanical - geotechnical rock properties, can be modelled and quantified by stochastic spatial simulations. This is demonstrated through a detailed, step- by-step application to the Puma deposit, a major nickel lateritic asset in Brazil, part of the Onça-Puma mining complex. To integrate the variability of the regolith profiles of the deposit, their thicknesses are calculated after an unwrinkling process is applied and the deposit is then jointly simulated using min/max autocorrelation factors (MAF). The realizations serve as geological boundaries within which Ni, Co, Fe, SiO2, MgO and Dry-tonnage factor (DTF) are subsequently jointly simulated directly at block support scale. The final result is a series of equally probable representations of the Puma deposit, which are used to quantify and assess the uncertainty about key aspects of the project at the Puma deposit, such as the uncertainty of the in-situ resources documented herein, and the strict control of the ore's quality that feeds the ferronickel processing plant. The framework presented shows the advantages of the MAF and direct block simulation approaches for the efficient joint simulation of spatially variant geological attributes of large deposits for industrial environments. The methods presented are general, new in the context of geotechnical and geomechanical engineering, and can assist in the modelling of spatial variability and quantification of uncertainty linked to geotechnical rock properties and pertinent lithological boundaries.

Effects of rock water content on CERCHAR Abrasivity Index

Cerchar Abrasivity Index (CAI) has been commonly used to represent rock abrasion for estimation of tool wear in rock excavation applications. This test is a simple and effective measure of rock abrasion but operating parameters can impact its results. This paper focuses on the influence of water saturation on CAI values based on laboratory testing of 33 sedimentary rock units collected from different regions of Pakistan. The tests include CAI measurements as well as engineering rock properties on both dry and saturated rocks. It was found that overall 79% of CERCHAR abrasivity index values measured on saturated rock surfaces “CAIsat” were less than the CERCHAR abrasivity index values measured on dry rock surfaces “CAIdry”. Meanwhile, 52% of CAIsat values showed significant reduction from CAIdry values in the statistical analysis of CAI results with significance level of 15% (α=0.15). Regression analysis was used to correlate CAIsat values with CAIdry, normally measured in CERCHAR testing. The proposed formula can be used to estimate CAIsat from result of laboratory testing where CAI reported is often CAIdry. This could lead into more accurate estimation of tool wear and related adjustments when CAI is used for estimation of tool wear when excavation is done under wet conditions. Multiple regression was also used to establish a predictive model of CAIsat with petrographical, wear indices and geotechnical rock properties of saturated rock samples. In addition, the validity of correlations of CAI with rock properties that are already published was evaluated.

Analysis of Methods of Landslide Processes Forecasting on Highways

This paper analyzes the methods of investigation of the stress-strain state of the landslide slope rock, as well as the research methods of geotechnical properties of rocks that form the sliding slope. The quantitative characteristics obtained during observations are necessary for grounding and selection of optimal anti-landslide measures, as well as to predict the occurrence of landslides. The geodesic observation techniques of landslide displacement which make it possible to predict with high accuracy a variety of simultaneous displacements within the general landslide zones and the manifestation of their features are considered.

Use of convolution and geotechnical rock properties to analyze free flowing discharge test

Discharge tests are conducted in order to determine aquifers transmissivity (T) and storage coefficient (S). However the interpretation of test data is not unique and the results may vary depending on adopted hypothesis. In this work, the convolution technique is applied for the reconstruction of observed drawdown curves aiming for the reduction of uncertainty. The interference between a flowing well and an observation well is evaluated in order to determine the hydrogeological parameters of the confined Guarani Aquifer System (Araujo et al. 1999). Discharge test data are analyzed according to the Jacob and Lohman (1952) method. The application of convolution enabled the determination of the most reliable solution. Obtained transmissivity (T = 411.0 m2/d) and storage coefficient (S = 2.75x10–4) are close to values estimated by direct evaluation of the geotechnical sandstone properties.

극한환경에 노출된 남극 암석의 물리적·역학적 특성

The Antarctic continent exposed to strong wind, very low temperature, and extremely dry condition. The freezing-thawing cycles under this extreme environment change the mechanical characteristics of rocks near the ground surface. To investigate the effect of freezing-thawing cycles under the extreme environment understand on geotechnical properties of rocks, rocks from the Antarctica were collected from two places: (1) West Antarctic Cape Burks and (2) East Antarctic Terra Nova Bay areas. The rock characteristics of these two areas were described and compared. For Terra Nova Bay area, rock characteristics of rocks near the surface and depths exceeding 2.9 m were examined. The `near-the-surface rocks` averages of absorption rate, P-wave velocity, and unconfined compressive strength were 0.56%, 3,717 m/s, and 109MPa, respectively; while, those values of `deep-sited rocks` were 0.24%, 4,670 m/s, and 88MPa. From the measurements, it was found that the effects of weathering were not significant on mechanical characteristics (strength) but were pronounced on physical characteristics(absorption and P-wave velocity).

Displacement-based numerical back analysis for estimation of rock mass parameters in Siah Bisheh powerhouse cavern using continuum and discontinuum approach

Back analysis as a modern observational method is a helpful technique for evaluation of soil and rock mass parameters and prediction of their mechanical behavior. Most back analysis techniques in geotechnical engineering problems are based on the methods that utilize the monitored data of stresses, strain and displacements. This technique is one of the prominent processes in design and evaluation of the stability of caverns that reveals the shortcoming of supports design and in fact is essential for evaluation of design parameters. Siah Bisheh pumped storage project with complex geometry, changeable geological formations and diverse geotechnical properties of rocks, is under construction on the Chalus River at the north of Iran. The underground complex consists of three main caverns placed near each other. In this study displacement based direct back analysis using continuum and discontinuum numerical modeling were applied and geomechanical properties of rocks, stress ratio and joints parameters were identified and then calculated parameters were compared with the initial design parameters. Both continuum and discontinuum modeling results were in a good agreement with measured displacements which confirm the numerical modelings correctness and back analysis results.

Long term stability assessment of Siah Bisheh powerhouse cavern based on displacement back analysis method

Siah Bisheh pumped storage powerhouse cavern with complex geometry, changeable geological formations and diverse geotechnical properties of rocks, is under construction on the Chalus River at the north of Iran. Powerhouse cavern is located near the lower dam reservoir and its crown is more than 30 m down the lower dam maximum lake level. After impounding of lower dam, powerhouse region will be located under saturated condition. Therefore long term stability assessment of the powerhouse cavern under saturated condition is unavoidable. In this study, displacement based direct back analysis using univariate optimization algorithm were applied and geomechanical properties of rocks, stress ratio and joints parameters were identified. Numerical modeling results are in good agreement with measured displacements using extensometers which confirm the numerical modeling accuracy and back analysis results. Then ordinary analysis of powerhouse cavern under natural condition using back analysis results were carried out. Results of analysis shows that powerhouse cavern is stable under natural condition and existing support system has suitable efficiency and could effectively control displacements. Finally, powerhouse cavern long term stability under saturated condition was analyzed. Results of analysis shows that after lower dam impounding, pore water pressure and uplift pressure in discontinuities around powerhouse cavern will arose and tend to local failure of powerhouse cavern in region 2nd and 3rd instrumentation arrays. To obtain powerhouse long term stability, it is recommended to construct a cutoff curtain around powerhouse cavern.

The Prediction of Geotechnical Rock Properties from Sonic and Neutron Logs

Sonic logs have been used successfully for estimating strength and static elastic moduli for coal measures strata at 18 sites in N.S.W. and Queensland, and empirical relationships between these geo...