Geomechanical Properties Of Rock Mass Research Articles

Back analysis of geomechanical parameters for rock mass under complex geological conditions using a novel algorithm

Geomechanical properties of rock mass are of vital importance for design optimization and stability evaluation in geotechnical engineering. Traditionally, they are estimated by laboratory experiments, in situ tests, and empirical classification, which ignore the scale effect, and may be not representative, leading to uncertainties of parameters. Back analysis method based on the monitoring displacement data provides the state-of-the-art tool for the estimation of geomechanical parameters. This paper proposed a novel back analysis method, which combined the optimized particle swarm optimization (OPSO) algorithm with the support vector machine (SVM) algorithm. And then, we cooperate the method with finite element method (FEM) forming the comprehensive method named OPSO-SVM-ABAQUS. This method has developed the standard PSO algorithm from two aspects for more powerful optimization capability and higher optimization precision. The OPSO algorithm is then used for the estimation of the SVM hyperparameters and the optimal values of geomechanical parameters. Furthermore, the performance of the proposed algorithm is compared with other six algorithms. Finally, the geomechanical parameters of the interlayered soft and hard rocks are calculated accurately, with the average error between the back-analyzed and assumed actual parameters to be 0.91 %. And the parametric investigations are implemented with the trained model. It dominates that the proposed algorithm is feasible for reasonable parameters in geotechnical engineering under complex geological conditions.

Review of the Geological Strength Index (GSI) as an Empirical Classification and Rock Mass Property Estimation Tool: Origination, Modifications, Applications, and Limitations

The geological strength index (GSI) is one of the most exceptional rock mass classification system which is used to evaluate very weak and highly jointed rock mass by different approaches and related to rock mass geomechanical properties including generalized Hoek & Brown constants, deformation modulus, strength properties, and Poisson’s ratio for an appropriate design of tunnels, caverns, and other engineering structures. The distinctiveness of this system over the rock mass rating (RMR), Q‐system, and other empirical methods is as follows: it utilized field observations, blockiness of rock mass, and surface joint characteristics during the evaluation process of rock mass and efficiently espoused as an empirical tool for estimation of geomechanical properties of rock mass required for pre‐post stability of engineering structures using numerical modeling. This study presents the review of the 19 years of research studies conducted by different researchers about the GSI in a systematic way, i.e., origination, modifications, applications, and limitations. Furthermore, this study will provide a better understanding to field professionals (geologists, mining and civil engineers) about the qualitative and quantitative estimation of the GSI and its application as an empirical estimating tool for an appropriate design of engineering structures in rock mass environments.

RMR and RHRS of Ngaizel Road cutting section, Aizawl, Mizoram

Due to unfavourable topographical features roads in hilly areas are usually small as compared to plain areas, therefore several problems may arise whenever rockfall occurs. One of the busiest domestic road in Aizawl i.e. Ngaizel road often encountered rockfall along its cutting slope. This road act as an important gateway which connects the southern parts of Mizoram. This road is packed with human activities which adds on the hazard level to rise high. The main factors that contribute to rockfalls include slope degree, geomechanical properties of rock mass and anthropogenic activities. Taking into consideration of all the adverse effect of rockfalls, RMR (Rock Mass Rating) become indispensable to identify the actual condition of rock mass on the slope of the study area. RMR classification is carried out to determine the geomechanical condition of slope rock mass and Rockfall Hazard Rating System (RHRS) is applied for identifying the hazard-prone area of rockfall along the cut slope of Ngaizel road. RHRS depends on various parameter which include slope height, annual precipitation, block size, block volume, decision sight distance, average vehicle risk, road width and rockfall history which mainly concern about the safety of pedestrians along the road. The RMR and RHRS study along Ngaizel cut slope provides a detailed and useful information about the geological condition and delineating the hazard level. The study also gave awareness and alertness about the actual condition of the area.

Variations in Mechanical Parameters of Rock Mass Affecting Shaft Lining / Zmiany Parametrów Mechanicznych Górotworu I Ich Wpływ Na Obudowę Szybową

Abstract The paper presents geomechanical properties of rock mass occurring in the initial section of shaft lining during its execution. The shaft being sunk is surrounded with cohesive soils, mainly clays with sand layers and silts. Such lithology causes that in various levels some parts of strata are saturated with water. This results in a considerable changeability of soil properties in time. With high water content, the soil is washed away leading to local loss of contact between shaft lining and surrounding soils. This, in turn, results in lack of proper support for curbs and shaft lining fracture in some sections. Engineering activity in such a case should embrace sealing injections in selected parts of the shaft in order to resume proper reinforcement in the lining-rock mass system. The studies of the soils surrounding shaft lining were supposed to help design curbs with increased bearing capacity. The tests of soils indicated that the angle of internal friction and cohesion do change not only at different depths but also at the same depth in different points of perimeter. It was also observed during the study that the mechanical parameters of the analyzed soils improve as the distance from the shaft lining increases, which clearly indicates change of soil properties in the direct neighborhood of the shaft. Considerable number of tests carried out in the study allowed to determine the relationship between water content and angle of internal friction or soil cohesion. The determined relationships can help to estimate change of soil properties under the influence of water with considerable precision. The reinforcement of curbs executed with the use of ground anchors allowed for further shaft sinking. The tests of concrete used in the shaft carried out in the analyzed section produced results similar to the values assumed in the project.

MATHEMATICAL AND FUZZY LOGIC MODELS IN PREDICTION OF GEOLOGICAL AND GEOMECHANICAL PROPERTIES OF ROCK MASS BY EXCAVATION DATA ON UNDERGROUND WORKS / MATEMATINIS IR NERAIŠKIOSIOS LOGIKOS MODELIAI APRAŠANT GEOLOGINES IR GEOMECHANINES UOLIENOS SAVYBES, NAUDOJANT POŽEMINIO KASINĖJIMO DUOMENIS

In underground works, the continual consciousness of geological and geomechanical properties of rock mass during drilling, is of major importance to optimize the works and the equipment used. In this paper, the mathematical relationship obtained from tunnel excavations, considering percussion drilling for blasting by a drilling machine and by a tunnel boring machine (TBM) are exposed. These mathematical relationships are useful in the percussion drilling case, to adjust the drilling parameter recorder (DPR) tools, and in the case of TBM to predict the rock mass geomechanical index (RMR). Taking into account the complexity of these mathematical models obtained, as a consequence of the affected variables and their relations, a fuzzy logic model based on parameters accessible to the drilling machine has been used in tricone bit drilling. Santrauka Atliekant požeminius uolienų gręžimo darbus ir optimizuojant darbus bei jiems naudojamą įrangą, labai svarbu prognozuoti geologines ir geomechanines uolienos savybes. Šiame darbe pateikiamos gautos matematinės išraiškos, taikant tunelių kasimo duomenis, gautus naudojant smūginio gręžimo ir tunelių gręžimo (TBM) įrangą. Šios matematinės išraiškos yra naudingos smūginio gręžimo metu koreguojant gręžimo parametro fiksavimo (DPR) duomenis, o naudojant TBM įrangą – nustatant uolienos geomechaninį indeksą (RMR). Atsižvelgiant į gautų matematinių modelių kompleksiškumą, t. y. į gautus parametrus ir jų sąryšius, naudotinas neraiškiosios logikos modelis, jungiantis parametrus, tinkamus trigalvio grąžto gręžimo įrangai.

Evaluation of boring machine performance with special reference to geomechanical characteristics

The duration of tunneling projects mostly depends on the performance of boring machines. The performance of boring machines is a function of advance rate, which depends on the machine characterizations and geomechanical properties of rock mass. There were various theoretical and empirical models for estimating the advance rate. In this paper, after determining the geomechanical properties of rock mass encountered in the Isfahan metro tunnel, the performance of the roadheader and tunnel boring machine (TBM) were then evaluated using various models. The calculation results show that the average instantaneous cutting rate of the roadheader in sandstone and shale are 42.8 and 74.5 m 3/h respectively. However the actual values in practice are 34.2 and 51.3 m 3/h. The operational cutting rate of the roadheader in sandstone and shale are 8.2 and 9.7 m 3/h respectively, but the actual values are 6.5 and 6.7 m 3/h. The penetration rate of the TBM in shale is predicted to be 50–60 mm/round.

Geomechanical properties of rock mass of Xingo dam, Brazil : Agagao, C J G; Souza, R J B; Abrahao, R A Proc 5th International Congress International Association of Engineering Geology, Buenos Aires, 20–25 October 1986V4, P2173–2180. Publ Rotterdam: A A Balkema, 1990

Geomechanical properties of rock mass of Xingo dam, Brazil : Agagao, C J G; Souza, R J B; Abrahao, R A Proc 5th International Congress International Association of Engineering Geology, Buenos Aires, 20–25 October 1986V4, P2173–2180. Publ Rotterdam: A A Balkema, 1990