Overburden Height Research Articles

Numerical modeling of seismic performance of shallow steel tunnel

Advanced numerical models can be used to complement experimental results and further elucidate their findings. This is particularly true when certain scaled model “adjustments” are incorporated in the testing scheme to reduce the testing cost or schedule. This study conducts comprehensive finite element modeling to simulate large-scale shaking table tests conducted by Kim et al. (2023) [1] to evaluate the seismic performance of steel tunnels. The numerical model was calibrated by comparing its predictions with the experimental observations in the initial tests. The calibrated model was then validated by comparing its predictions with the results obtained from other test models and subjected to different input ground motions. The validated model was employed to comprehensively investigate the effects of the testing scheme parameters including the input motion time scaling, tunnel burial depth, and soil relative density. It was found that reducing the time scale factor during the tests led to decreased seismic responses. It was also found that the presence of overburden soil on top of the tunnel resulted in higher seismic bending moment values, and that higher overburden height increased both lateral and vertical soil pressures on the tunnel side walls and top slab. In addition, lateral soil distortion and tunnel deformations were found to be directly correlated with the overburden soil height. Furthermore, in the absence of overburden soil, there was a significant amplification in horizontal soil acceleration. The results demonstrated that lower-density sand bed experienced greater acceleration amplification and larger displacement, and the tunnel experienced larger lateral soil pressure and higher racking. Additionally, the results revealed that subjecting the same soil bed to several shaking tests affected its stiffness, and hence affected the test observations in the subsequent tests. This should be considered when planning shaking table tests. Finally, the strain values and racking ratios obtained from the numerical simulations and the shaking tests were in agreement with the values obtained from the FHWA procedure.

An analytical investigation of soil arching induced by tunneling in sandy ground

The soil mass above the tunnel generally yields due to the tunnel volume loss. Depending on the amount of the volume loss, soil unit weight, overburden height and internal friction angle, a stress arching zone and a loosened zone can be formed above the tunnel. In this study, a two-dimensional stress field resulting from the tunnel volume loss inside the soil mass above the tunnel is investigated analytically. By presenting an analytical solution in rectangular coordinates, new equations were developed to evaluate and estimate the magnitude of vertical, horizontal and shear stress components inside the soil mass. The vertical stress changes resulting from the tunnel volume loss were analyzed and the height of the arching zone and the loosened zone above the tunnel were determined. In addition, a parametric study was conducted to evaluate the effect of soil unit weight, soil internal friction angle, surcharge on the ground surface and overburden depth on the stress distribution in the soil above the tunnel. The results showed that depending on the depth of the tunnel and the strength of the surrounding soil, the arching and loosened zones may or may not be created. In order to validate the proposed solution, the vertical stress distribution along the tunnel crest has been compared with some experimental and numerical data. It can be stated that the proposed solution provides relatively good approximations for the vertical stress component. The results of this research show that a safe and economical support system for tunnels in sandy ground can be designed using the proposed solution.

Stability evaluation of room-and-pillar rock salt mines by using a flat jack technique - A case study

Room-and-pillar mining is commonly employed for the extraction of rock salt in underground mines. Pillar stress is a major concern in these mines as it is directly related to stability and mineral recovery. In this study a flat jack method was used to measure pillar stresses in three underground rock salt mines in Pakistan. The field work included determination of in-situ stress, in-situ elastic modulus, recording of field variables (pillar length and width, height and width of opening, opening width to height ratio, extraction ratio, and overburden height) and collection of salt block samples. The geomechanical properties of rock salt (uniaxial compressive strength, Young's modulus, Brazilian tensile strength, and density) were also determined to estimate overburden stress, pillar strength, and factor of safety (both estimated and actual). It was found that the measured pillar stresses are proportional to the overburden stress values, with their magnitude ranging from 6.05 MPa to 11.97 Mpa, and the pillars were found to be stable. Regression analysis was performed to develop statistical models for in-situ stress and in-situ elastic modulus. Finally a quick guideline chart was developed to determine the suitable length of pillar for a given span and required level of safety. Keywords: flat jack, room-and-pillar mining, in-situ stress, factor of safety, regression analysis.

Disastrous Mechanism of Water Burst by Karst Roof Channel in Rocky Desertification Mining Area in Southwest China

With the development of coal mining in rocky desertification mining area in Southwest China, water burst is becoming an important disaster in coal mine. In order to grasp the evolution characteristics of water gushing channels in coal mining in rocky desertification mining area, the 1402 working face in Xintian Coal Mine is taken as the research object, and the occurrence of aquifers on the roof of the working face is analyzed, and the water filling path of the aquifers is explored. Besides, the evolution characteristics of water passage in coal seam mining are comprehensively analyzed, by the methods of physical similarity simulation, numerical simulation, and microseismic monitoring. The results show that the key water resource is the atmospheric precipitation, which enters the mine through the original karst fissure and mining-induced fissure. With the continuous advance of working face, the fracture height of overburden increases gradually. Specifically, when the advancement distance of working face exceeds 135 m, the water-conducting cracks in the overlying strata develop to the bottom boundary of the Yulongshan limestone aquifer, and then, the mining-induced fracture and aquifer are conducted; when the working face advances 190 m, the overall overburden mining fissure is divided into fissure opening zone and fissure closed zone. Meanwhile, most of the microseismic events occur in the middle part of the karst roof, and the maximum height of microseismic event is 40 m away from the bottom boundary of the Yulongshan limestone, during the advancing process of the working face. When the mining fissure is connected with the original karst fissure, atmospheric precipitation enters the aquifer through the original karst fissure and enters the gob of working face through the mining fissure. The research results provide the references for prediction and prevention for the water burst disaster in rocky desertification mining area in Southwest China.

Study of the Indoor Model Test and CEL Simulation of Jacking Force in the Vertical Tunnelling Method

The jacking force is one of the important parameters affecting the construction process in the vertical tunnelling method. To study the dynamic changing process of jacking force with the jacked distance and the influencing factors of the maximum jacking force, both the indoor model test and numerical simulation were conducted. In the model test, we investigated the influence of the height of the soil and water content. The results indicated that the higher the overburden height was, the greater the jacking force. Moreover, the water content enhanced the compressibility of the soil and had little effect on the maximum jacking force. Additionally, the coupled Eulerian–Lagrangian (CEL) approach was used to simulate the vertical jacking construction. In the numerical simulation, we investigated two construction factors (jacking speed and the standpipe outer diameter) and four soil parameters (cohesion, internal friction angle, elastic modulus, and Poisson’s ratio). Before that, the CEL simulation results were compared with test data to prove the rationality of the CEL approach, and the two were in good agreement. The results showed that among the six influence parameters, according to the influence degree on the maximum jacking force from large to low, the outer diameter of the standpipe, internal friction angle, cohesion, elastic modulus, jacking speed, and Poisson’s ratio were ranked. In addition, the jacking speed of numerical analysis was suggested to be 0.2 m/s. The research results in this paper can provide a reference for the construction of the vertical tunnelling method.

Rock engineering challenges in post-mining

A legacy of environmental challenges with abandoned mines remains for many generations. The challenges include among others: (i) danger from sinkholes above shallow old mine workings and (ii) effects of rising water level in deep mines. Abandoned shallow mines show after > 20 years no damaging subsidence. Sinkholes, however, may still develop by structurally controlled failure. Main contributing factors are the geometry of an underground opening. Geological factors include the resource type (orebody or seam), height of rock overburden and cohesive soil, water flow and discontinuity spacing. The latter determines the bulking factor of the displaced roof and thus the maximum caving height. For steeply inclined openings it must be considered whether the caved rock moves down the dip and prevents self-stabilization. Rising water levels in deep abandoned mines may induce seismic events. Despite significant progress in monitoring and numerical methods there is still no appropriate geological or rock mechanical basis for explaining or predicting water pressure induced seismic events. Some research topics are suggested to approach this issue.

Three-Dimensional Numerical Investigation of the Interaction Between Twin Tunnels

The construction of twin tunnels is a mandatory guideline and a prevailing practice in either conventional or mechanized tunneling. Nevertheless, most of the design methods for calculating the tunnel loads focus on single tunnels, neglecting thus the potential interaction between neighboring tunnels. The effect of such interaction can be significant, especially for closely-spaced twin tunnels. In this context, this paper investigates via parametric 3D finite element analyses the interaction between deep, parallel-twin, circular and non-circular tunnels excavated with a conventional (i.e., non-TBM) method and supported with shotcrete lining. The numerical investigation focuses on the axial forces acting on the primary support of the tunnels by examining the effect of a wide range of geometrical (pillar width, overburden height, tunnel diameter and section (shape), lagging distance), geotechnical (strength and deformability of the surrounding rockmass, horizontal stress ratio), structural (thickness and deformability of the shotcrete lining) and construction parameters (full- or partial- face excavation and support of the tunnels). The results of the analyses indicate that the construction of the subsequent tunnel influences the loads of the precedent. The stress state of the single tunnel is used as the reference for the quantification of the interaction effect. The output is presented in normalized design charts of the quantified interaction effect on the axial forces versus key geomaterial and geometry parameters to facilitate preliminary estimations of primary support requirements for twin tunnels. Furthermore, nomographs are provided for preliminary assessments of the optimum pillar width (spacing) between twin tunnels, which practically eliminates the interaction effect.

Three-Dimensional Numerical Analyses of Perpendicular Tunnel Intersections

This paper investigates the effect of constructing a junction tunnel, intersecting an existing main tunnel at a normal angle, via parametric 3D Finite Element (3D-FE) analyses. The 3D interaction between the tunnels significantly modifies the stress state of the primary support and the surrounding rockmass at the intersection area, compared to that of the single tunnel (quasi plane strain problem), thus making 3D-FE analyses necessary for the realistic design of the primary support at the junction area. The numerical investigation includes deep, circular intersecting tunnels with the junction tunnel excavated, after the main tunnel, via a conventional (non-TBM) method and supported with shotcrete lining. The parametric analyses are performed for a wide range of junction tunnel’s diameter, overburden height, in-situ horizontal stress ratio, strength and deformability of the surrounding rockmass. They focus on calculating the axial forces acting on the primary support at the intersection area before, during and after the construction of the junction tunnel. In addition, they identify the extent of the zone influenced by the tunnel interaction. The results of the analyses indicate that the construction of the junction tunnel causes significant additional compressive loading at the springline of the main tunnel. In contrast, the crown/invert of the opening of the main tunnel is subjected to either compressive loading or unloading (often reaching tensile loading). The results of the analyses are presented in normalized design charts of the axial forces, versus key geomaterial and geometry parameters to facilitate preliminary estimations of primary support requirements at tunnel junctions.

An Investigation of the Seismic Interaction of Surface Foundations and Underground Cavities Using Finite Element Method

In this study, the seismic interaction of surface foundations and underground cavities was investigated. For this purpose, a parametric study of geometric dimensions of the foundation and cavity, their location, and the effect of the interaction between surface foundations and underground cavities was evaluated. The variable parameters include the ratio of the overburden height to the foundation width (H/B = 0.5, 1 and 2), the location ratio of the cavity to the foundation width (X/B=0, 2 and 8) and the ratio of the cavity diameter to the foundation width (d/B=0.5, 1 and 2), respectively. The accuracy of the finite element method was evaluated using a laboratory study and it was found that the used method provides an accurate prediction of tunnel behavior.The results indicated that by increasing the overburden height, the stress on the tunnel surfaces was increased for all values of X/B (the horizontal tunnel distance to the foundation width). Therfore, in the case where the tunnel is located exactly along the center at the bottom of the foundation (X/B=0, d/B=2), the maximum stress generated is approximately 2.13 times greater than its corresponding value in the ratio of the depth to width of 0.5 (X/B=0, d/B=0.5). It can be concluded that the higher overburden height, the greater stresses caused by the dynamic loads of the earthquake on the tunnel wall.

A theory of loosening earth pressure above a shallow tunnel in unsaturated ground

SummaryA theory is proposed to evaluate the loosening earth pressure (vertical earth pressure after excavation) acting on a shallow tunnel in unsaturated ground with an arbitrary groundwater level. The theory is developed based on the limit equilibrium theory, combining soil–water characteristic curves, Mohr–Coulomb failure criteria, and effective stress for unsaturated soils. The proposed theory is applied to predict the vertical distribution of loosening earth pressure in unsaturated ground, which shows a significant difference from that in saturated ground. In unsaturated ground, suction contributes to the increase in effective loosening earth pressure and shear resistance. The remarkable effects of groundwater depth, soil type, and scale of overburden height and trapdoor width on loosening earth pressure are also revealed. Based on the soil–water characteristic curve, the degree of saturation decreases, which causes wet density to decrease and the total and effective loosening earth pressures to have contrary tendencies. Moreover, effective loosening earth pressures vary with soil type as the degree of saturation varies. The total loosening earth pressures are, however, very similar regardless of soil type, because wet density and shear resistance have similar tendencies. The proposed theory provides a valid model for loosening earth pressure in unsaturated ground that will be useful for shallow tunnel excavations.

Evaluation and Optimization of the Effective Parameters on the Shield TBM Performance: Torque and Thrust—Using Discrete Element Method (DEM)

Cutterhead torque and thrust are the two main designing parameters of the shield TBM, which have to be evaluated and optimized, based on the interaction between the TBM and excavated material. This study employs the discrete element method (DEM) to simulate the tunneling procedure of the line-7 of Tehran underground urban train tunnel utilizing the micro mechanical parameters calculated from back analysis on direct shear tests. The resultant torque and thrust are then compared against the actual parameters and then with those estimated from the numerical analyses. This result shows that DEM is able to estimate the TBM torque and thrust applying actual boundary conditions and material properties for the model. Furthermore, the impact of ground properties, overburden height, linear and radial velocity on cutterhead torque and thrust and its performance are evaluated and optimized.

Predicting Convergence Rate of Namaklan Twin Tunnels Using Machine Learning Methods

Convergence prediction of tunnels has always been one of the important issues of geotechnical projects. Developing prediction models is a good approach to predict convergence, when there is no knowledge of the possibility of convergence occurrence in the future. In this study, convergence rates of two tunnels from the Namaklan twin tunnel were predicted by different types of machine learning methods. Artificial neural networks (ANNs), multivariate linear regression (MLR), multivariate nonlinear regression (MNR), support vector regression (SVR), Gaussian process regression (GPR), regression trees and ensembles of trees (ET) were applied to predict the convergence rate (CR). The six parameters of cohesion (c), internal friction angle (Φ), uniaxial compressive strength of rock mass (σc), rock mass rating, overburden height (H) and the number of installed rock bolts (NB) were selected as predictor parameters. The dataset was collected via field investigations and laboratory experiments. The results showed that the MLP–ANN model can successfully predict the CR with the determination coefficient (R2) of 0.93. The RBF–ANN model is also successful in predicting the CR with R2 of 0.81. The SVR, MNR and MLR models were also constructed to obtain an empirical formula for predicting the CR. Comparing among the three models showed that the SVR model is more successful (R2 = 0.66) than the MNR and MLR models with R2 of 0.65 and 0.61, respectively. However, the SVR model is placed in the next rank of the ANN models. Among the rest models, except the ET model (R2 = 0.66), the RT and GPR models have no good capability for the prediction of the CR. In total, assessing the statistical indices indicated that the ANNs are superior to the other models in predicting the CR. However, the SVR model could be considered to be a reliable predictive model for convergence rate estimation.

Effect of Overburden Height on Hydraulic Fracturing of Concrete-Lined Pressure Tunnels Excavated in Intact Rock: A Numerical Study

This study investigated the impact of overburden height on the hydraulic fracturing of a concrete-lined pressure tunnel, excavated in intact rock, under steady-state and transient-state conditions. Moreover, the Norwegian design criterion that only suggests increasing the overburden height as a countermeasure against hydraulic fracturing was evaluated. The Mohr–Coulomb failure criterion was implemented to investigate failure in the rock elements adjacent to the lining. A pressure tunnel with an inner diameter of 3.6 m was modeled in Abaqus Finite Element Analysis (FEA), using the finite element method (FEM). It was assumed that transient pressures occur inside the tunnel due to control gate closure in a hydroelectric power plant, downstream of the tunnel, in three different closure modes: fast (14 s), normal (18 s), and slow (26 s). For steady-state conditions, the results indicated that resistance to the fracturing of the rock increased with increasing the rock friction angle, as well as the overburden height. However, the influence of the friction angle on the resistance to rock fracture was much larger than that of the overburden height. For transient-state conditions, the results showed that, in fast, normal, and slow control gate closure modes, the required overburden heights to failure were respectively 1.07, 0.8, and 0.67 times the static head of water in the tunnel under a steady-state condition. It was concluded that increasing the height of overburden should not be the absolute solution to prevent hydraulic fracturing in pressure tunnels.

Bemessungskonzept für Druckschächte bei Nutzung des passiven Gebirgswiderstands

AbstractThe proposed method can be seen as an adaption of the ”Seeber“ concept considering developments in geomechanics, calculation methods and steel technology over the last decades. When exposed to inner pressure, the cracking condition is transgressed and steel linings will not protect the rock mass against cracking. Accordingly, the post‐failure behaviour of the rock mass is an essential basis for structural design. The effects of crack water pressure on radial displacements and the width of gaps are considered. The resistant behaviour of the rock mass is determined by its minor primary principal stress. Under mountain ridges and slopes, there is no correlation between the minor stresses and the height of overburden. Obviously damage cases in concrete lined tunnels are the result of inappropriate assessment of principal stresses. A better approach is proposed based on fundamental considerations and FE calculations. Crack water pressure close to the level of the minimal principal stress will induce progressive hydraulic fracturing in the rock mass, which requires safe waterproofing sealing of the shaft. Grouting the coaxial gap in rock mass is a firm part of any design concept. In shafts sealed by membranes, the capability to bridge fissures must be proved by tests. In steel lined shafts, the usable passive resistance of rock mass is determined by the acceptable radial displacement.

A First Order Quantification of Effects of Uncertainties in Hydro-fracturing Parameters on Tunnel Ovalization Estimates

In-situ stresses are always present in rock-masses due to gravitational and tectonic forces. Excavation of a tunnel in such a pre-stressed media causes deformation of tunnel cross-section. Ovalization of tunnels due to in-situ stresses in rock-mass is an important design parameter. For estimation of tunnel ovalization, state of in-situ stresses needs to be determined first. In-situ stresses determined through hydro-fracturing technique (HFT) are dependent upon the three HFT parameters: (a) shut-in pressure, (b) re-opening pressure, and (c) fracture orientation. A critical review of previous studies indicates that HFT parameters are subjected to uncertainties due to (1) limitations of testing procedures and equipment, (2) assumptions and subjective engineering judgment associated with interpretation of test results, and (3) inherent variability of geological formations. Therefore, tunnel deformation estimates based on in-situ stresses determined through HFT would also be affected by these uncertainties. In this paper, a framework based on the first-order second moment method is developed to evaluate the effects of uncertainties in hydro-fracturing test data on tunnel deformation. The analysis indicates that uncertainty in tunnel deformation depends upon the uncertainty levels as well as magnitude of the three HFT parameters along with Poisson’s ratio, height of overburden, and the angular location of the point on the tunnel periphery where deformation is being estimated. It is also found that among the three parameters, the shut-in pressure has the maximum relative contribution in the resulting uncertainties in tunnel ovalization with an average of 68% (± 8% standard deviation). The proposed methodology is explained through an example case-study from Bukit Timah Granite rock-mass of Singapore. It is found that for a range of coefficient of variation of shut-in and re-opening pressure from 0 to 50%, the maximum coefficient of variation of tunnel deformation varies between 63 and 332%. In view of such high uncertainties, it is recommended that uncertainties of HFT parameters must be taken into account in the design procedure to avoid unsound engineering judgments.

The role of dilatancy in shallow overburden tunneling

The mechanical behavior of sandy ground during shallow circular tunneling is explored for various overburden heights H (=0.5D, 1.0D, 1.5D and 2.0D; D is the diameter of the tunnel) and various dilatancy coefficients (ψ/ϕ = 0, 1/3, 1/2, and 1; ϕ and ψ are the internal friction angle and dilation angle, respectively) through finite difference analyses. The ground is modeled as a linear elastic-perfectly plastic material that employs the Mohr–Coulomb yield criterion and obeys the non-associated flow rule. The ground reaction curve is applied in conjunction with the stress path as a conceptual tool for interpreting the mechanical response of the ground to tunneling. It is revealed that, at a certain relaxation value, a yield zone develops during tunneling and extends to the surface. This relaxation value increases with increases in the overburden and ψ/ϕ values for the cases of less shallow tunnels (i.e., H = 1.0D, 1.5D and 2.0D), while for the shallowest case (H = 0.5D), the extent of the yield zone to the ground surface is not sensitive to the ψ/ϕ value. The shear strain due to tunneling also increases with an increase in the ψ/ϕ value. Moreover, the ψ/ϕ value affects the radial displacement and the surface settlement due to tunneling. The magnitudes of the surface settlement and the radial displacement at the tunnel crown both decrease with an increase in the ψ/ϕ value. The relative difference in the displacement at the tunnel crown between the upper bound and lower bound values, ψ/ϕ (at the last computed stage), increases with an increase in the overburden height. It is recommended, therefore, that careful consideration be given to the dilatancy angle in the case of relatively less shallow tunnels.

Sensitivity analysis of the conception of small scale district heating networks on the thermal conductivity of the surrounding soil

Heat distribution via pre-insulated plastic bonded piping systems will become of major importance for covering the primary energy consumption of EU and will be of vital importance for the energy and heat turnaround. Utilizing efficiency potentials of combined heat and power (CHP) and integrating (industrial) waste heat and renewable energy contents within these grids, low temperature (and low-ex) heat sources might be exploited. Thus, energetic contents unsuitable for electrical energy supply are utilized in order to diminish greenhouse gas emissions and minimize primary energy needs.Distribution of heat requires accurate planning and network design for the expected service time of several decades. This applies for existing networks as well as for future networks. During planning and conception different load scenarios (of today and in future) must be considered. Since the design of existing networks was done in the past, this paper focusses on the requirements for the conception and planning of heating networks in the near future. Because of low temperature (and low-ex) heat sources, the expansion of district heating networks in EU will be linked to modifications in the network design and planning. A sensitivity analysis was carried out for relevant input parameters in low temperature networks. The analysis showed a significant influence of the conductivity of the bedding material as well as the overburden height on heat losses. For the given set of reference parameters, the energy efficiency potential of systems for heat distribution is approximately 10 %.

Effect of soil type on nail pull-out resistance

Nowadays, soil nailing is widely used to stabilize slopes and excavations. The bond strength is integrated shear strength along the interface area between grout and soil. Choosing a value for bond resistance is one of the effective parameters in nailed wall design, which is generally determined by the values proposed by FHWA guidelines. A designer uses a high safety factor that makes the design safe but sometimes it is not economical. Therefore, in this study, an attempt is made to investigate the effects of overburden, injection pressure and soil strength parameters on the bond strength of nails in field. For this research, five different sites in Tehran were considered with a total number of 20 soil–nail pull-out test. Values such as cohesion, friction angle, modulus of elasticity, moisture content, percentage of coarse- and fine-grained soil were determined in the laboratory, and the effect of these parameters on the bond strength was examined. The results of the tests showed that by increasing injection pressure and overburden height, bond strength increases, and that the effect of injection pressure is much more than that of overburden height. Finally, a relationship was suggested to estimate the bond strength in terms of soil specifications and overburden height.

The Dangerous Condition of Ground during High Overburden Tunneling (A Case Study in Iran)

Knowledge of the ground condition and its hazards can play an important role in the selection of support and suitable excavation method in underground structures. Water transport tunnel is one of the most important structures with regard to the goal of excavation, special conditions and limitations considered in the design and execution of them. Beheshtabad Water Conveyance Tunnel with 64930 meters length, 6 meters final diameter is the largest water Conveyance tunnel in Iran. Because of high over burden and weak rock in the most of tunnel path, the probable hazardous of the ground condition such as squeezing and rock burst must be studied. Squeezing stands for large timedependent convergence during tunnel excavation. This phenomenon occurs in weak rocks and deep conditions. Besides, the height of overburden in some of the zone tunnel is about 1200 meters. The occurrence of this phenomenon is always together with the instantaneous release of strain energy stored in the rock materials, causing the harm to the personal equipment and the collapse of underground structures. The existence of high thickness overburden in some the zones of this project indicates the high potential of rock burst hazard. In this research, the length of the tunnel has been partitioned into sections using the interpreted geological, geophysical studies and borehole data. After evaluating rock burst and squeezing potential with alternative analytical and experimental methods for each section, the results of dierent methods were compared with each other. Results predict low to moderate squeezing potential and moderate to high rock burst potential for some panels of the tunnel.

Prediction of representative deformation modulus of longwall panel roof rock strata using Mamdani fuzzy system

Deformation modulus is the important parameter in stability analysis of tunnels, dams and mining structures. In this paper, two predictive models including Mamdani fuzzy system (MFS) and multivariable regression analysis (MVRA) were developed to predict deformation modulus based on data obtained from dilatometer tests carried out in Bakhtiary dam site and additional data collected from longwall coal mines. Models inputs were considered to be rock quality designation, overburden height, weathering, unconfined compressive strength, bedding inclination to core axis, joint roughness coefficient and fill thickness. To control the models performance, calculating indices such as root mean square error (RMSE), variance account for (VAF) and determination coefficient (R2) were used. The MFS results show the significant prediction accuracy along with high performance compared to MVRA results. Finally, the sensitivity analysis of MFS results shows that the most and the least effective parameters on deformation modulus are weathering and overburden height, respectively.