Geomechanical Monitoring Research Articles

STRAIN GAUGES FOR MEASURING DEFORMATIONS IN MINE OPENING ELEMENTS

Specifics of new solutions for measuring deformations in mining openings by strain gauges and specifics of forecasting changes in a mine geomechanical situation have been presented in the form of the case study of conditions of LLC GIPS KNAUF gypsum mine. A definition has been given for geomechanical monitoring station, results of tests in mine conditions have been also presented.

Geomechanical monitoring of temporal lining in railway tunneling in complex geological conditions

The article describes the integrated method and results of deformation–wave monitoring of temporal lining in railway tunneling in complex geological conditions in the south of Western Siberia. 3D geometric parameters of temporal lining are measured by laser scanning at a span of 3 months, which enables comparing actual 3D models of temporal lining and rocks in reinforced tunnel section. Based on the data obtained at various times of observation, shifting of unmarked points of temporal lining and deformation of tunnel walls and arch were determined. High density scanning allows remote identification of comparatively small zones where structure of rocks and state of lining are changed. The authors analyze seismic vibration of rocks under hammering, which shows that peak spectral densities of elastic wave in rocks are conditioned by low-frequency (pendulum) wave generated at siltstone and coal interface, and are related with dimension of joints and with mechanical properties of rocks.

Experimental Investigations of the Effectiveness of the "Geocomposite" Method of Soil Grouting in the Beds of Buildings on Backfill Sands

Means of geomechanical control are examined for effectiveness of stabilization during grouting of fill sands by the "Geocomposite" method. Results are presented for control of soil stabilization beneath the foundation of a building under construction during one-time and repeated injections after appropriate studies within the framework of geomechanical monitoring.

Practical experience of geomechanical monitoring in underground mineral mining

The article addresses the issues of geomechanical monitoring in underground mineral mining. A brief review covers existing software and hardware for estimation of stress state and properties of rocks and the results of in situ trial of an integrated tool set. The authors offer the geomechanical monitoring structure using a package of instrumental, visual and numerical methods for the assessment of mechanical condition and its alteration in rocks and in structural components of mines. Thereupon, the geomechanical state control system have been developed and introduced in a number of operating mines. For the stability assessment of structural elements in mines and for the decision-making on mining safety, the rock mass limit state criteria are defined.

Shallow Strip Foundations Joined by Gently Inclining Envelopes on Highly Compressible Soils

Computed behavioral characteristics are presented for a soil bed subject to nonuniform loading, and a computational model and method of controlling interaction between shallow strip foundations and the soil bed with use of strip foundations connected by gently inclining envelopes are proposed. Results are cited for experimental investigations. Computational data and results of geomechanical monitoring of the construction of a 17-story tenement building are presented.

A New Approach in Permeability and Hydraulic-Flow-Unit Determination

Summary Building an integrated subsurface model is one of the main goals of major oil and gas operators to guide the field-development plans. All field-data acquisitions from seismic, well logging, production, and geomechanical monitoring to enhanced-oil-recovery (EOR) operations can be affected by the accurate details incorporated in the subsurface model. Therefore, building a realistic integrated subsurface model of the field and associated operations is essential for a successful implementation of such projects. Furthermore, using a more reliable model can, in turn, provide the basis in the decision-making process for control and remediation of formation damage. One of the key identifiers of the subsurface model is accurately predicting the hydraulic-flow units (HFUs). There are several models currently used in the prediction of these units on the basis of the type of data available. The predictions that used these models differ significantly because of the assumptions made in the derivations. Most of these assumptions do not adequately reflect realistic subsurface conditions, thus increasing the need for better models. A new approach has been developed in this study for predicting the petrophysical properties and improving the reservoir characterization. The Poiseuille flow equation and Darcy equation were coupled, taking into consideration the irreducible water saturation in the pore network. The porous medium was introduced as a domain containing a bundle of tortuous capillary tubes with irreducible water lining the pore wall. A series of routine and special core analysis was performed on 17 Berea sandstone samples, and the petrophysical properties were measured and X-ray diffraction (XRD) analysis was conducted. In building the petrophysical model, it was initially necessary to assume an ideal reservoir with 17 different layers, each layer representing one Berea sample. Afterward, by the iteration and calibration of the laboratory data, the number of HFUs was determined by use of the common HFU model and the proposed model accordingly. A comparative study shows that the new model provides a better distribution of HFUs and prediction of the petrophysical properties. The new model provides a better match with the experimental data collected than the models currently used in the prediction of such parameters. The good agreement observed for the Berea sandstone experimental data and the model predictions by use of the new permeability model shows a wider range of applicability for various reservoir conditions. In addition, the model has been applied to a series of core-analysis data on low-permeability Medina sandstone, Appalachian basin, northwest Pennsylvania. The flow-unit distribution by use of the proposed model shows a better flow-zone distinction, and the permeability/ porosity relationship has a higher confidence coefficient.

The Role of Geomechanical Observation in Continuous Updating of Thermal-Recovery Simulations With the Ensemble Kalman Filter

Summary In-situ thermal methods such as steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) are widely used in oil-sand reservoirs. The physics of such thermal processes is generally well-understood, and it has been shown that rock properties are highly influenced by the geomechanical behavior of the reservoir during these recovery processes. Geomechanics improves the process dynamically, and its response can depict the progress of production within a reservoir. However, the potential of geomechanical monitoring is not usually practiced. With increased implementation of highly instrumented wells and communication technologies providing real-time monitoring data from different sources, combining available data into reservoir geomechanical simulations can improve updating numerical models and the prediction process. This research explores effective uses of geomechanical observation data for history matching and types of geomechanical observation sources adequate for thermal recovery. The ensemble Kalman filter (EnKF), combined with an iterative geomechanical coupled simulator, has been chosen as the data-assimilation algorithm to update the model continuously on the basis of geomechanical observations and production data. The results show that considering geomechanical modeling and observation improves history matching when geomechanical behavior plays a role in the process.

Vibration effect of earthquakes in abandoned medieval mine

The information on seismic loading and vibration effect is significant when assessing stability of underground spaces located in the vicinity of seismic active areas. Underground structures are well known to be earthquake resistant. Nevertheless, the existence of discontinuities makes them vulnerable to collapses, particularly in case of shallow underground openings. This study presents results of long-term seismic monitoring performed in the shallow medieval mine. This mine is located at a distance of about 25 km southeast of Nový Kostel focal zone (West Bohemia, Czech Republic), where seismic activity in the form of seismic swarms occurs. The most intensive earthquakes were documented here in the past with local magnitude M L =5.0. During two intensive seismic swarms from the Nový Kostel focal zone in 2008 (M L ≤3.8) and 2011 (M L ≤3.7), almost 2000 earthquakes were recorded at the seismic station in the mine. Vibration effect underground was analysed together with results of geomechanical monitoring. Based on the measured data, vibration effect in the mine was extrapolated for an expected more intensive earthquake with the local magnitude M L =5.0.

Mock-up experiments on permeability measurement of concrete and construction joints for air tightness assessment

Concrete permeability is subject to various test conditions, and on-site measurement at in situ structural scale is much preferable. This paper presents an experimental study to measure the permeability of concrete linings and their construction (placing) joints between old and new concretes using a novel in situ permeability testing system. Using the developed system, we performed in situ scale permeability tests of rectangular concrete specimens with dimensions of 500 × 500 × 2800 mm3, within which the construction joints were artificially placed. From this model experiment, we verified an effective applicability of the system to both low permeability concrete matrices and highly permeable construction joints thanks to its selective capability of gas or water permeability test, depending on the air/water tightness of tested materials. The experimental results presented in this paper also showed that the intrinsic permeability of the construction joint could be higher than that of the concrete matrices by orders of magnitude (101–104 times), but it could be reduced to as low as those of the concrete matrix by pasting a bonding agent on the interfacing surfaces. As a result of geomechanical monitoring during the experiment, the opening displacement of construction joints with relatively higher stiffness values showed a reversible deformation when the gas injection pressure was unloaded, which is much preferable in a storage performance perspective of underground lined rock caverns.

Geomechanical time series and its singularity spectrum analysis

The multifractal analysis is applied to the study of geomechanical monitoring time series. Estimation of singularity spectra parameters within moving time window for this monitoring time series provides a possibility for splitting the history of observations into few adjacent fragments which could reflect e.g. hidden different states of the rock massif in the vicinity of measuring station. In this contribution, analysis of time series of measured distances is presented. A laser distance meter is used for measuring the height of a large chamber in the medieval Jeroným Mine (Czech Republic). This time series separation into individual segments using singularity spectra parameters is important for possible comprehensive analysis of data in individual time periods and/or between individual time periods.

Specific roof behavior in the southern wing of the Upper Kama potash salt deposit

The authors consider a number of geomechanical monitoring methods for the underworked salt rock behavior, including visual control of its specific structural features, measurement of displacements using contour and depth reference points, and assessment of stresses in the surrounding rock mass. It is proposed to assess stresses in salt rocks using long spacing measurement methods without modeling-based recovery of stresses from measured strains if possible.

On joint geomechanical and geophysical monitoring in mines

The case study, conducted for the seam No. 4 of the Vorkuta coal district, illustrates the enhancement of the interpretation of the microseismic data through their using in combination with calculation of stresses and numerical simulation of seismic events.

Athens Metro – Elliniko Extension TBM Tunnel Construction

The present paper is describing the TBM tunnelling and all related geological, geotechnical aspects, geomechanical monitoring, TBM construction and other special civil works issues for a 5.5 km metro construction project of the Athens metro line 2 extension to Elliniko. This paper is linked to the recent overall publication "Project Description, Structuring and Implementation" of the same project in the Magazine Geomechanics and Tunnelling within the edition of June 2008.

Information systems for geomechanical monitoring in underground structures

Results of the development of a monitoring system for underground structures, which makes it possible to unite and utilize data bases intended for various purposes (geographic, geologic, ecologic), and also results of numerical modeling of the interaction between a structure and rock mass, and data derived from field measurements within the framework of the design of the geographic information system (GIS), are cited for a specific entity. Utilizing the GIS, fixing of the structure in space will make it possible to assess more graphically and informatively the condition of the structure, and the degree of its safety, as well as the influence that it exerts on the adjacent setting and surrounding geologic medium during its construction and service.

Universal time provisioning in a distributed seismic-acoustic system for rock mass geomechanical monitoring

A structure of hardware-software universal time provisioning in a seismic-acoustic system for rock mass geomechanical monitoring is described. The structure was tested at a mine in the Chitinskaya Region. A measure of inaccuracy of universal time counting is analyzed and calculated.

Numerical modeling of seismic and aseismic events in three-dimensional problems of rock mechanics

The numerical method for joining geomechanical and seismological monitoring at mines is extended to 3D problems.

Block Model for Realization of Prediction Component in Geomechanical Monitoring

The problem on possible creation of monitoring system ensuring reliable prediction of catastrophic manifestations of rock pressure is considered. The mathematical model of hierarchical block mass is presented for describing the development of nonlinear consolidation and deconsolidation processes. The analytical methods are proposed for the model investigation to reveal possible origination of catastrophes.

One approach to the prediction of rock bursts

Thus, as a result of the experimental discovery of previously unknown pendulum waves, the elementary carriers of which are geoblocks differing in hierarchic level, with dynamic-kinematic characteristics that depend on the stress-strain state of the rock masses and the dimensions of the focal zones of rock bursts and explosions, we are able to propose a new approach to the prediction of catastrophic events. Here, as diagnostic indexes with respect to the critical stages of stress concentration for focal zones of rock bursts that are being formed, we can use the angular characteristic θ of the conical envelope of the μ-wave packets and their energy characteristics Ψ1 and Ψ2. With such an approach, seismograms from technological explosions can be used as integral information in a new system of geomechanical monitoring.

Experimental assessment of the stress-strain state of the rock in the bed of the Sayano-Shushenskoe hydroelectric power plant

bed itself, but is also the initial background on which dynamic loads due to seismic effects are superposed. The mechanism responsible for interaction between the body of the dam and the rock bed ultimately reflects the seismic safety of the structure and requires increased attention, especially in the stage when the entity is brought on line. Of paramount significance here are experimental observations of the mechanical processes that take place both in the body of the dam, and in the rocks of the bed [1]. It is important to compare computed estimates obtained in design with actual data on the one hand, for example, to adapt the three-dimensional finite-element model of the dam to actual conditions. On the other hand, empirical information on the stress-state of specific segments will contribute to the database of the system used for geomechanical monitoring of processes occurring in the zone of the shore abutments under cyclically varying loads caused by the regime under which the reservoir is filled and drawn down. A program for complex experimental investigation of the stress-strain state of the rock bed of the high dam for the Sayano-Shushenskoe hydroelectric power plant* calls for, among other things, stationary observations by several geophysical (ultrasonic profiling, seismic inspection) and geomechanical methods, including the hydraulic rupture of rock in a hole. In our study, we discuss the results of two series of experiments conducted by the method of hydraulic rupture of holes in a section of the left-bank abutment Of the dam when the reservoir had been filled close to, respectively, the maximum 540-m (October 1996) and minimum 500-m (May 1997) elevations.t The procedure used for the experimental studies, the makeup of the equipment, the recording apparatus, and the method employed for data interpretation are described in [2]. The selection of this method was not random and was predetermined by its correspondence to a series of requirements set forth for long-term stationary observations: firstly, by the repeatability of measurements, i.e., the possibility of taking measurements at the same point of the mass as external conditions vary; and, secondly, by the serviceability under rather complex conditions where the water content of the rocks is high and the natural jointing of the mass is increased; these conditions are critical for the majority of familiar methods based on strain measurement. Attention as also focused on the scale of the method (the possibility of conducting measurements at a distance to tens of meters with a measurement base of the order of 0.5 m) and a quality rather rare for mechanical methods: direct measurement of a parameter possessing the dimensions of stress; this precludes additional determination of some deformation constants of the rocks. Of course, the question concerning the sensitivity and resolution of the shaft variant of equipment, which is intended for operation in deep underground workings remains unanswered as applies to different rock and hydrogeological conditions. True, preliminary estimates of the expected stress level of the order of 10 MPa in sections of the shore arch supports, which had made it possible to calculate a positive result, and also the data derived from a trial series of experiments with the

Deep hydraulic fracture imaging: Recent advances in tiltmeter technologies

Standard metallic coaxial cables were installed at the Waste Isolation Pilot Plant (WIPP) to monitor shear deformation in the roof, floor and walls of a newly excavated underground room. The WIPP is being developed near Carlsbad, New Mexico, for the disposal of transuranic nuclear wastes in bedded salt 655 meters (2, 150 feet) below the surface. Data collected from WIPP geomechanical monitoring are used to characterize conditions, confirm design assumptions, and understand and predict the performance of deep salt excavations. In the past, the installation of metallic coaxial cables provided an excellent means of locating the areas of shear deformation using time domain reflectometry (TDR). However, this monitoring technique has been advanced by quantifying the amount of shear deformation occurring in the underground installations. To quantify field data, shear tests were conducted in the laboratory to simulate a typical field installation in salt rock undergoing shear deformation. Shear offsets were quantified with respect to change in waveform characteristics. This paper presents a comparison of field data collected at the WIPP to laboratory test results in order to quantify waveform characteristics to shear deformation. By quantifying the TDR monitoring system, the amount of deformation as well as the are a of deformation can be defined. This provides an excellent, as well as inexpensive, means of monitoring shear deformation in underground excavations. This work was supported by the U.S. Department of Energy under DOE Contract No. DE-AC04-86AL31950.