Geological Prediction Research Articles

TBM in Azad Kashmir region of Pakistan: in situ stress measurements for rockburst prevision

Using the authors’ experience, this paper details the in situ stress measurements in twin tunnel boring machine (TBM) tunnels of the Neelum Jhelum hydropower project, located in the Azad Kashmir region of north-east Pakistan in foothills of the Himalayas, with overburdens up to 2000 m and high tectonic stresses in very complex geology. The ability to predict the likelihood, location, severity and number of rockbursts directly impacts on the tunnel safety and daily production rates. This, combined with the lack of previous project experience in similar conditions, has required the use of all the available advanced geological prediction methods: forward probing, tunnel seismic tomography, continuous microseismic monitoring and in situ stress measurements were used. These methods, except in situ stress measurements, only gave an indication of likelihood and severity of rockbursts. The in situ tests provided the actual ground stresses and their orientations. The in situ stress results contradicted the forecasts based on the classical empirical rules combining stress analysis and rock strength. This paper is focused on the in situ stress measurements carried out behind the two TBMs and details the information obtained and how data were interpreted and integrated to support excavation, prevention and control of rockbursts, which improved tunnel safety and productivity.

A method suited to survey of shallow high resolution Survey and survey in busy streets of a city ? Landsoner

Landsoner is the abbreviation of extremely elastic reflection wave recording continues profiling with extremely small offset and vary wide band frequency. It has following characteristics: (a) Small-offset single is used; (b) Under situation of using hammer source can be excited and be received reflection wave with frequency 10Hz-4000Hz of depth of 1.200m; (c) It is unnecessary that the geophones f ixed on the ground. On this characteristics the wave with different frequency band can be got that can greatly rise resolution, and can keep away from the noise of acoustic wave, direct wave, reflected wave, surface wave, specially can keep away from the noise of vibration of pedestrians, cars and the other machines on a city. When using landsoner method survey line with broken line can be used. There is no need to statics in mountainous region for this method. On the time-section of figure of Landsoner a karst cave can clearly be reflected. Landsoner method has been successfully used in shallow high resolution survey in mountainous region or in a busy city, in survey karst caves, in geological prediction forward from working face in a tunnel construction and in examining quality ofconcrete structures.

A new method for clastic reservoir prediction based on numerical simulation of diagenesis: A case study of Ed1 sandstones in Bozhong depression, Bohai Bay Basin, China

The use of seismic exploration technique to provide reliable reservoir information is a conventional method. However, due to its quality and resolution reasons, it cannot satisfy the detailed research and characterization of reservoirs, especially the clastic reservoir with thin sand body. Diagenesis is a fundamental process in the development and formation of all petroleum reservoirs and is a major contributor to their ultimate physical properties. Based on numerical simulation of diagenesis, a new prediction method called geology prediction techniques is presented to simulate the evolution of the diagenetic stages, diagenetic facies and porosity of clastic reservoirs and ultimately for favorable reservoir prediction. It emphasizes the idea of dynamic quantitative research dominated by process recovery, the most important of which is the establishment of mathematical models, including mineral dissolution models, mineral cementation models and sediment compaction models using the experimental data in study area and the results of previous studies. The essence of this method is illustrated, and its effectiveness is proved using Ed1 clastic sandstones in the Bozhong depression, Bohai Bay Basin, China. At present, the reservoir is in the early diagenetic stage B (IB) and the middle diagenetic stage A1 (IIA1). The major diagenetic processes that influence the porosity of the sandstones in study area are mechanical compaction, carbonate cementation, quartz cementation, clay cementation, feldspar dissolution and carbonate dissolution. There are three types of sandstones including fine sandstone, siltstone, and argillaceous siltstone, and the variation range of primary porosity of these sandstones is from 26% to 38%. Compaction and carbonate cementation are the main reasons for porosity reduction, with porosity loss percentage by compaction (P-Com) and porosity loss percentage by cementation of carbonate (P-C-Car) being 53.1% ~ 7.8% (av. 41.9%) and 53.1% ~ 7.8% (av. 18%), respectively, while carbonate dissolution and feldspar dissolution can greatly improve reservoir physical property, with porosity increase percentage by dissolution of carbonate (P-D-Car) and porosity increase percentage by dissolution of feldspar (P-D-Fel) being 0 ~ 9.9% (av. 8.9%) and 0 ~ 27.8% (av. 9.4%), respectively. The predicted porosities match the measured porosities well. Cited as : Qian, W., Yin, T., Hou, G. A new method for clastic reservoir prediction based on numerical simulation of diagenesis: A case study of the Ed1 clastic sandstones in the Bozhong depression, Bohai Bay Basin, China. Advances in Geo-Energy Research, 2019, 3(1): 82-93, doi: 10.26804/ager.2019.01.07

Surficial and Deep Earth Material Prediction from Geochemical Compositions

Prediction of true classes of surficial and deep earth materials using multivariate spatial data is a common challenge for geoscience modelers. Most geological processes leave a footprint that can be explored by geochemical data analysis. These footprints are normally complex statistical and spatial patterns buried deep in the high-dimensional compositional space. This paper proposes a spatial predictive model for classification of surficial and deep earth materials derived from the geochemical composition of surface regolith. The model is based on a combination of geostatistical simulation and machine learning approaches. A random forest predictive model is trained, and features are ranked based on their contribution to the predictive model. To generate potential and uncertainty maps, compositional data are simulated at unsampled locations via a chain of transformations (isometric log-ratio transformation followed by the flow anamorphosis) and geostatistical simulation. The simulated results are subsequently back-transformed to the original compositional space. The trained predictive model is used to estimate the probability of classes for simulated compositions. The proposed approach is illustrated through two case studies. In the first case study, the major crustal blocks of the Australian continent are predicted from the surface regolith geochemistry of the National Geochemical Survey of Australia project. The aim of the second case study is to discover the superficial deposits (peat) from the regional-scale soil geochemical data of the Tellus Project. The accuracy of the results in these two case studies confirms the usefulness of the proposed method for geological class prediction and geological process discovery.

Research on Advanced Tunnel Geological Detection and Prediction Technology Based on Three-dimensional Dynamic Point Source Induced Polarization Method

This paper introduces the basic principle of the comprehensive geological prediction method of tunnel, and summarizes the key points and key points of the comprehensive geological prediction method of tunnel in the construction of highspeed railway tunnel. The comprehensive geological prediction method and tunneling effect are compared. The results show that the comprehensive geological prediction method is effective and accurate. At last, this paper expounds the problems existing in the advanced geological prediction of high-speed railway tunnel, and puts forward the corresponding solutions.

Early Mars Climate History: Characterizing a “Warm and Wet” Martian Climate With a 3‐D Global Climate Model and Testing Geological Predictions

AbstractObservations of Late Noachian‐Early Hesperian‐aged Martian surfaces reveal valley networks, lakes, degraded craters, and putative oceanic shorelines, often interpreted to require a persistent “warm and wet” climate, characterized by mean annual temperature >273 K and abundant rainfall. We simulate this “warm and wet” climate (global mean annual temperature ~ 275 K) with a 3‐D global climate model to determine whether these features could have formed in this climate through rainfall activity. We find that rainfall is limited in abundance and areal distribution, precipitation is dominated by snowfall, and highlands temperatures are <273 K for the majority of the year. We conclude that, in this simulated climate scenario, (1) Late Noachian‐Early Hesperian valley networks and lakes could not have formed through rainfall‐related erosion, (2) crater degradation by rainsplash and runoff is not predicted, (3) global clay formation through long‐lived rainfall, fluvial activity, and warm temperatures is unlikely, and (4) the presence of a rainfall‐ and overland flow‐fed northern ocean is improbable.

Geological models and controlling factors of gas content in marine–terrigenous shale in the Southern Qinshui Basin, China

Geological prediction models for gas content in marine–terrigenous shale under the effects of reservoir characteristics and in situ geological conditions, were established using methane isothermal adsorption, high temperature/pressure methane isothermal adsorption, total organic carbon, X-ray diffraction, mercury porosimetry, porosity in net confining stress, and field desorption methods. Results indicated that the adsorption capacity of marine–terrigenous shale has a linearly positive correlation with total organic carbon content and maturity. Clay and quartz minerals are the two main components of inorganic minerals in marine–terrigenous shale, with an average content of 54.3% and 36.9%, respectively. Adsorption capacity of marine–terrigenous shale is slightly positive correlated with clay content, while it exponentially decreases with increasing quartz content. The effects of in situ temperature and reservoir pressure on adsorption capacity in marine–terrigenous shale are also significant. The adsorption capacity of marine–terrigenous shale shows a clear decreasing trend as temperature increases, while it increases with increasing reservoir pressure. The porosity of marine–terrigenous shale is characterized by highly stress-sensitive, decreasing exponentially with increasing effective stress, which results in a more complex occurrence of free gas in deep shale reservoirs. In addition, gas saturation for the shale samples was calculated based on the results of field desorption, after which geological prediction models of total gas, adsorbed gas, and free gas were established while considering the coupled effects. Adsorbed gas, free gas, and total gas content all initially increase as burial depth increases, and then eventually decrease. Adsorbed gas content and free gas content have a positive correlation with total organic carbon content and porosity, indicating that the total gas content at different burial depths is mainly controlled by the total organic carbon content and porosity.

Prediction of karst for tunnelling using fuzzy assessment combined with geological investigations

This paper presents a method for predicting karst features before and during tunnel construction. The prediction of karst consists of two components: an initial karst prediction using a fuzzy assessment system to evaluate the underground karst state and an updating karst prediction where appropriate geological investigation methods are selected based on the assessment of underground karst state. The investigation results are then used to update the underground karst state. The initial assessment system is based on a fuzzy comprehensive evaluation method. Nine influence factors are selected as the evaluation indices for the underground karst state, and each index is quantitatively rated to four grades. The membership of the evaluation index is determined by using a membership function, and the weights of these indices are distributed by using a fuzzy Analytical Hierarchy Process. The fuzzy transform principle and maximum membership degree principle are applied to determine the underground karst state level. Based on the assessment result, several techniques for geological investigation, including the seismic reflection method, ground penetrating radar, infrared water detection, transient electromagnetic method, and advance probe boreholes, are recommended to predict the location, size, and distribution of karst features ahead of tunnel faces. These geological investigations have different characteristics and can be combined to improve the accuracy of the geological prediction. The appropriate combination of investigation methods is selected using the assessed underground karst state, and the investigation results are also used as the input to update the underground karst state. The proposed method can improve the prediction of karst in tunnelling. An application of this method was performed in the Doupengshan tunnel project.

Geological Prediction Ahead of Tunnel Face in the Limestone Formation Tunnel using Multi-Modal Geophysical Surveys

Tunnel construction in typical karst topography face the risk which unknown geological condition such as abundant rainwater, ground water and cavities. Construction of tunnel in karst limestone frequently lead to potentially over-break of rock formation and cause failure to affected area. Physical character of limestone which consists large cavity prone to sudden failure and become worsen due to misinterpretation of rock quality by engineer and geologists during analysis stage and improper method adopted in construction stage. Consideration for execution of laboratory and field testing in rock limestone should be well planned and arranged in tunnel construction project. Several tests including Ground Penetration Radar (GPR) and geological face mapping were studied in this research to investigate the performances of limestone rock in tunnel construction, measured in term of rock mass quality that used for risk assessment. The objective of this study is to focus on the prediction of geological condition ahead of tunnel face using short range method (GPR) and verified by geological face mapping method to determine the consistency of actual geological condition on site. Q-Value as the main indicator for rock mass classification was obtained from geological face mapping method. The scope of this study is covering for tunnelling construction along 756 meters in karst limestone area which located at Timah Tasoh Tunnel, Bukit Tebing Tinggi, Perlis. For this case study, 15% of GPR results was identified as inaccurate for rock mass classification in which certain chainage along this tunnel with 34 out of 224 data from GPR was identified as incompatible with actual face mapping.

Conception and Exploration of Using Data as a Service in Tunnel Construction with the NATM

Abstract The New Austrian Tunneling Method (NATM) has been widely used in the construction of mountain tunnels, urban metro lines, underground storage tanks, underground power houses, mining roadways, and so on. The variation patterns of advance geological prediction data, stress–strain data of supporting structures, and deformation data of the surrounding rock are vitally important in assessing the rationality and reliability of construction schemes, and provide essential information to ensure the safety and scheduling of tunnel construction. However, as the quantity of these data increases significantly, the uncertainty and discreteness of the mass data make it extremely difficult to produce a reasonable construction scheme; they also reduce the forecast accuracy of accidents and dangerous situations, creating huge challenges in tunnel construction safety. In order to solve this problem, a novel data service system is proposed that uses data-association technology and the NATM, with the support of a big data environment. This system can integrate data resources from distributed monitoring sensors during the construction process, and then identify associations and build relations among data resources under the same construction conditions. These data associations and relations are then stored in a data pool. With the development and supplementation of the data pool, similar relations can then be used under similar conditions, in order to provide data references for construction schematic designs and resource allocation. The proposed data service system also provides valuable guidance for the construction of similar projects.

Chemical kinetics evaluation and its application of natural gas generation derived from the Yacheng Formation in the deep-water area of the Qiongdongnan Basin, China

The natural gas generation process is simulated by heating source rocks of the Yacheng Formation, including the onshore-offshore mudstone and coal with kerogens of Type II2-III in the Qiongdongnan Basin. The aim is to quantify the natural gas generation from the Yacheng Formation and to evaluate the geological prediction and kinetic parameters using an optimization procedure based on the basin modeling of the shallow-water area. For this, the hydrocarbons produced have been grouped into four classes (C1 C2 C3 and C4-6). The results show that the onset temperature of methane generation is predicted to occur at 110°C during the thermal history of sediments since 5.3 Ma by using data extrapolation. The hydrocarbon potential for ethane, propane and heavy gaseous hydrocarbons (C4-6) is found to be almost exhausted at geological temperature of 200°C when the transformation ratio (TR) is over 0.8, but for which methane is determined to be about 0.5 in the shallow-water area. In contrast, the end temperature of the methane generation in the deep-water area was over 300°C with a TR over 0.8. It plays an important role in the natural gas exploration of the deep-water basin and other basins in the broad ocean areas of China. Therefore, the natural gas exploration for the deep-water area in the Qiongdongnan Basin shall first aim at the structural traps in the Ledong, Lingshui and Beijiao sags, and in the forward direction of the structure around the sags, and then gradually develop toward the non-structural trap in the deep-water area basin of the broad ocean areas of China.

A 3D Multi-scale geology modeling method for tunnel engineering risk assessment

A method for 3D multi-scale geology modeling is proposed for assessing tunnel engineering risk. Risk assessments have varying requirements at various different construction stages, therefore the proposed model can be modified for different scales. The regional scale 3D geological model, based on regional field surveys of geological boundary and attitude, is proposed for conducting preliminary evaluations with limited geological sampling data and the Hermite radial basis function (HRBF). The project scale geological model, based on updating and refining the regional scale model with dense drilling and geological prediction data, couples the geological body model for surrounding rock and the tunnel model. This project scale model is appropriate for performing pre-evaluations of tunnel construction. Once construction has begun, continuous rock structure surface information from the newly exposed tunnel face is incorporated into the outcrop scale geological model. It is based on a Monte-Carlo algorithm for conducting dynamic evaluations during construction. These modeling methods are applied to a case study, railway tunnel engineering of the Yuelongmen tunnel in China.

Typical Underwater Tunnels in the Mainland of China and Related Tunneling Technologies

Abstract In the past decades, many underwater tunnels have been constructed in the mainland of China, and great progress has been made in related tunneling technologies. This paper presents the history and state of the art of underwater tunnels in the mainland of China in terms of shield-bored tunnels, drill-and-blast tunnels, and immersed tunnels. Typical underwater tunnels of these types in the mainland of China are described, along with innovative technologies regarding comprehensive geological prediction, grouting-based consolidation, the design and construction of large cross-sectional tunnels with shallow cover in weak strata, cutting tool replacement under limited drainage and reduced pressure conditions, the detection and treatment of boulders, the construction of underwater tunnels in areas with high seismic intensity, and the treatment of serious sedimentation in a foundation channel of immersed tunnels. Some suggestions are made regarding the three potential great strait-crossing tunnels—the Qiongzhou Strait-Crossing Tunnel, Bohai Strait-Crossing Tunnel, and Taiwan Strait-Crossing Tunnel—and issues related to these great strait-crossing tunnels that need further study are proposed.

Response Characteristics and Experimental Study of Underground Magnetic Resonance Sounding Using a Small-Coil Sensor

Due to its unique sensitivity to hydrogen protons, magnetic resonance sounding (MRS) is the only geophysical method that directly detects water and can provide nondestructive information on subsurface aquifer properties. The relationship between the surface MRS signal and the location and characteristics of aquifers using large-coil (typically 50–150 m) sensors has been discussed based on forward modelling and experiments. However, few researchers have studied underground MRS using a small-coil sensor. In this paper, a parametric study and a large-scale physical model test were conducted to shed light on the critical response characteristics of underground MRS using a small-coil sensor. The effects of the size and number of turns of the transmitter coil and receiver coil, the geomagnetic declination, the geomagnetic inclination, and the position, thickness, and water content of a water-bearing structure on the performance of the underground MRS were studied based on numerical simulations. Furthermore, we derived the kernel function and underground MRS signal curves for a water-bearing structure model based on the simulations. Finally, a large-scale physical model test on underground MRS using a small-coil sensor was performed using a physical test system for geological prediction of tunnels at Shandong University. The results show that the inversion results of the physical model test were in good agreement with the physical prototype results. Using both numerical modeling and physical model tests, this study showed that underground MRS using a small-coil sensor can be used to predict water-bearing structures in underground engineering.

Construction risks of Huaying mount tunnel and countermeasures

The Chongqing-Guang’an motorway is planned to cross Huaying mount at Jingguan town of Chongqing city. The whole mount is a colossal anticline whose core is consisted of coal measure strata (upper Permian Longtan formation P2l) and the limbs are limestone strata (middle Triassic Leikoupo formation T2l and lower Triassic Jialingjiang formation T1j). The tunneling is full of risks of collapse, gas explosion or gas outburst, water (mud) inrush, gas inrush because of existence of faults, high pressure gas, karst tectonics and coal goafs around the tunnel. In order to cope with the high risk, two main countermeasures were taken to ensure security of construction. One is geology prediction, and the other is automatic wireless real-time monitoring system, which contains monitoring of video, wind speed, poisonous gas (CH4, CO, H2S, SO2), people location, and automatic power-off equipment while gas contents being more than warning threshold. These ascertained the engineering safety effectively.

Application of comprehensive prediction method of water inrush hazards induced by unfavourable geological body in high risk karst tunnel: a case study

ABSTRACTWhile tunnelling in karst terrains, karst fissure water may endanger the safety of tunnel engineering and cause geological disasters such as water inrush. To ensure the safety of tunnel construction, in investigation stage, engineering geological and hydrogeological conditions of Jigongling Tunnel was analysed firstly. In design stage, a reasonable prediction method combining with optimization principle was selected to calculate the water inflow according to the geological and hydrogeological conditions analysed in the investigation stage. Then the advanced geological prediction was divided into different classes based on the water inflow. To make an accurate prediction, tunnel seismic prediction method, transient electromagnetic method, induced polarization method and advanced geological drilling were comprehensively applied in construction stage. This method combined with geology analysis, water inflow calculation and classification of advanced geological prediction is successfully applied in the Jigongling Tunnel of Fanba Expressway, and has provided a reference for the similar engineering constructions.

Forming Condition and Geology Prediction Techniques of Deep Clastic Reservoirs

Forming Condition and Geology Prediction Techniques of Deep Clastic Reservoirs

The application of geological advanced prediction in tunnel construction

This article studied the theoretical composition of tunnel geological prediction (TGP), put forth the concepts of broad-sense TGP, narrow-sense TGP and comprehensive TGP and established a technical solution of broad-sense TGP on this basis, including three steps: macroscopic prediction of unfavorable geologies in the tunnel area, prediction of unfavorable geological bodies in the tunnel (i.e.: narrow-sense TGP) and alarm on approaching of geological hazards in the tunnel. The article also researched the methods and technical means of short-term geological prediction and long-term geological prediction of narrow-sense TGP and proposed a fault parameter prediction method, a surface geological body projection prediction method and a precursor prediction method of unfavorable geological bodies in the tunnel. In addition, the article also introduced the concept of alarm on approaching of geological hazards in tunnel construction and established a method for alarm on approaching of geological hazards in the tunnel. In the end, the article concluded that the implementation of comprehensive prediction is the most effective means to achieve expected prediction effect and increase prediction accuracy.

Mechanism of water inrush in tunnel construction in karst area

ABSTRACTWith the rapid developing trend of long, large and deep construction characteristics for underground engineering in the world, China has the largest number of karst tunnels with the wide scales and great difficulties. As the hydrogeological conditions are becoming unprecedentedly complex, water inrush disaster becomes the bottleneck problem for the further development of traffic tunnels. Based on the statistical analysis of a large number of cases of water inrush in karst tunnels, influence factors of water inrush have been put forward from the view of karst hydrogeological factors and engineering disturbance of human factors. Karst hydrogeological factors include geological defect, strata dip, formation lithology, landform and underground level. Human factors of engineering disturbance include excavation and reinforcement geological prediction, monitoring and measurement of surrounding rock. It also introduces some geological disasters caused by the water inrush in tunnel excavation. In terms of the formation of water inrush channel, water inrush types are divided into geological defects inrush, non-geological defects inrush and the combination. Conclusions will be beneficial to further research on hazards control of underground construction.

A new comprehensive geological prediction method based on constrained inversion and integrated interpretation for water-bearing tunnel structures

Advanced geological predictions and ascertainment of the water-bearing geological structures in front of the tunnel face are effective ways to ensure the safety of tunnel construction. Comprehensive geological predictions are often used to obtain adverse geological conditions in front of the tunnel face, and the comprehensive comparison analysis on various prediction methods can help to reduce multiplicity of solutions and improve reliability. However, in the conventional comprehensive prediction system, the prediction data for each method is separately inverted and processed, so the problem of multiple solutions in detection results for each category actually cannot be solved. Therefore a new comprehensive geological prediction method is proposed in this paper based on constrained inversion and integrated interpretation for water-bearing tunnel structures to solve the problem. Firstly, four preferred prediction methods are selected to meet the needs of the advanced detection of water-bearing structure. They are seismic reflection method, transient electromagnetic method, 3D resistivity method and ground penetrating radar (GPR) method. Then, a constrained inversion method of 3D resistivity is proposed based on the inequality and spatial structural constraints. Inequality constraint characterises the electrical resistivity variation range of the detection area, and its prior information is mainly from the geological inference and core-drilling analysis. Spatial structural constraint characterises the geological structure boundary and shape, its prior information is mainly derived from some more effective methods for geological tectonic boundary recognition such as seismic reflection and GPR methods, and it also can be derived from the disclosure by drilling exploration. The role of resistivity constrained inversion to reduce the multiple solutions of prediction is mainly reflected in data processing, and the role of integrated interpretation to reduce the multiple solutions of prediction is mainly reflected in the result interpretation process. Meanwhile, the responding characteristics of methods of seismic reflection, electromagnetism, 3D resistivity, GPR and others to the water-bearing geological structure are summarised from the differences of elasticity, electrical conductivity and dielectric constant. Therefore, an integrated interpretation guideline for water-bearing structures is proposed. Finally, a new comprehensive geological prediction technology system is established through combining the constrained inversion and the integrated interpretation. Numerical examples and engineering applications show that this method can take full advantage of the prior information of inequality constraints and spatial structures, and together with the integrated interpretation on the comprehensive geological prediction results, it has a significant effect in eliminating the false anomalies of inversion, reducing the multiple solutions of inversion and improving prediction accuracy.