Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

Tao Wang, Chao-Sheng Tang, Bin-Qiang Ouyang et al.

Afeez K. Popoola, Kareem Ramzy Aboayanah, Seyed Mohammad Hosein Seyed Ghafouri et al.

The microstructure and fabric of rocks largely control their mechanical behavior, and their spatial variations can lead to anisotropic behavior. Metamorphic rocks such as gneiss exhibit anisotropy, and characterizing this anisotropy is crucial in geoscientific and engineering applications including geothermal plays, active fault zones, and mining sites. We investigate a foliated gneiss from the French River area of the Canadian Shield to determine its mechanical properties and assess the impact of anisotropy across different scales. We combined micro-scale experiments (e.g. nanoindentation and optical and electron microscopy), with meso-scale experiments (e.g. unconfined compressive strength (UCS) and indirect tensile test), to attempt bridging the micro-to meso-scale elastic property gap. Our results show that micro- and meso-mechanical properties of gneiss are orientation-dependent across scales. Young's modulus, upscaled from nanoindentation testing, varied between 51 GPa and 74 GPa, while meso-scale Young's modulus from UCS tests varied between 45 GPa and 54 GPa. The ultrasonic velocities (P- and S-wave) exhibited anisotropy of 26% and 24%, respectively, while the estimated UCS anisotropy was 30%, with the highest values observed in the direction parallel to the foliation. The direction of the mineral alignment forming the foliation plane plays a crucial role in determining the failure pattern of the rock. We observed predominantly tensile failure in samples with 0°–15° foliation plane angle, shear-slip failure for samples with 20°–65°, and a conjugate shear failure in the sample at 90° foliation plane angle to the loading direction. These findings provide insight into the anisotropic (orientation-dependent) characterization of foliated metamorphic rocks, which can be useful in rock engineering applications and numerical simulations.

JIN Changyu, WEI Zhenlin, CHEN Tianyu

This study investigates the influence of water accumulation in goaf on the stability of surrounding rock in a coal mine in Shanxi Province via field test, laboratory experiment and numerical simulation. Specifically, we established 3D geometric models of water bodies and goaf in water-bearing goaf based on 3D laser scanning and sonar. We then conducted permeability test on coal rock under different degrees of damage, and obtained permeability variation patterns. We then analyzed the stability of surrounding rock near water-cut goaf using numerical software by considering the dynamic changes of permeability. Results show that: ① pore water pressure exerts significant impact on the surrounding rock and overlying rock mass. ② The surrounding rock is prone to water seepage and percolation after the old goaf is flooded. ③ A large range of plastic zone with low stability is observed in the coal pillar between the goaf and roadway due to mining disturbance and water seepage. Therefore to ensure the safety of underground production, it is suggested to increase temporary underground drainage facilities for in-time water discharge to avoid flooding accidents.

Yong Fang, Bin Zhuo, Yubo Wang et al.

Clogging is a major geohazards risk in mechanized tunnelling through cohesive soils. Clay clogging results from the high adhesion between the clay and metal. Based on the water film theory and Reynolds fluid equation, the interfacial adhesion between metal and soil is simplified in this study as viscous hydrodynamic behavior between planes. Considering the influence of capillary force and the viscous force of water film at the interface between metal and soil, a theoretical calculation model of interfacial adhesion between metal and soil is established. The influence of water film thickness and separation rate on the interfacial adhesion between metal and soil is qualitatively analyzed. Then, the adhesion stress between the clay and the metal surface was tested with a pullout test and the influence of moisture content, pullout rates and types of clay minerals on the adhesion stress was analyzed. Finally, the calculation model of adhesion force was compared with the experimental results. The calculation model of soil adhesion stress established in this paper can quantitatively describe the relationship between soil adhesion force and moisture content and can also qualitatively reveal the influence mechanism of soil moisture content on adhesion stress.

Ke Man, Liwen Wu, Xiaoli Liu et al.

Abstract Due to the complexity of underground engineering geology, the tunnel boring machine (TBM) usually shows poor adaptability to the surrounding rock mass, leading to machine jamming and geological hazards. For the TBM project of Lanzhou Water Source Construction, this study proposed a neural network called PCA–GRU, which combines principal component analysis (PCA) with gated recurrent unit (GRU) to improve the accuracy of predicting rock mass classification in TBM tunneling. The input variables from the PCA dimension reduction of nine parameters in the sample data set were utilized for establishing the PCA–GRU model. Subsequently, in order to speed up the response time of surrounding rock mass classification predictions, the PCA–GRU model was optimized. Finally, the prediction results obtained by the PCA–GRU model were compared with those of four other models and further examined using random sampling analysis. As indicated by the results, the PCA–GRU model can predict the rock mass classification in TBM tunneling rapidly, requiring about 20 s to run. It performs better than the previous four models in predicting the rock mass classification, with accuracy A, macro precision MP, and macro recall MR being 0.9667, 0.963, and 0.9763, respectively. In Class II, III, and IV rock mass prediction, the PCA–GRU model demonstrates better precision P and recall R owing to the dimension reduction technique. The random sampling analysis indicates that the PCA–GRU model shows stronger generalization, making it more appropriate in situations where the distribution of various rock mass classes and lithologies change in percentage.

Philip I. Batanov, Ilyas F. Abkadyrov, Artem V. Degterev et al.

The paper provides information on the objectives, methods, targets and some preliminary results of the expeditionary work carried out within the framework of the RSF project No.21-17-00049 by the employees of the Institute of Volcanology and Seismology of the FEB RAS, Institute of Marine Geology and Geophysics of the FEB RAS, Pacific Geographical Institute of the FEB RAS and Trofimuk Institute of Petroleum-Gas Geology and Geophysics of the SB RAS in 2022 and 2023. The main objectives of the expedition were geological volcanological, hydrogeological, geophysical, tephrochronological, and paleoseismological studies. In accordance with the set objectives, field teams were formed, which began work in February 2022. On the basis of the data obtained during the expedition, previously unknown hydrothermal manifestations and seismic events on Iturup Island were identified. A number of geophysical and paleomagnetic surveys were carried out.

LI Xiaomei 1, LING Xiaodong 2, WANG Fang 1, MI Zhankuan 1, ZHAN Xinjie 1

It is important to study the stress deformation and stability of foundation by accurately testing the strength index of soils. For the triaxial tests under low confining pressures (less than 100 kPa), the influences of the piston friction and the rubber membrane can not be ignored. At the same time, the test accuracy and measuring range of equipments are also the important factors that should be considered. This study attempts to explore the influences of factors such as the piston friction and the rubber membrane on the test results by carrying out unconfined compressive strength tests under different conditions and triaxial consolidated undrained shear tests of different equipments, and to explore how to measure the compressive and shear strengths of samples according to the existing test conditions, so as to provide reliable data for design, construction and numerical calculation. In view of the shortcomings of domestic triaxial test equipments, reasonable suggestions are put forward, and it is expected that the triaxial test equipments should be further transformed and upgraded from mechanical manufacturing so as to promote the researches and development of precise triaxial test equipments in China.

Kang Chen, Shengyang Yuan, Shenxin Pan et al.

Weathered Red mudstone is widely distributed in Sichuan basin. The compacted weathered red mudstone has been used as subgrade fill materials of high-speed railway in southwestern of China. Dynamic responses of such materials under cyclic loading are critical to long-term stability of subgrade. Shakedown concept is widely employed in characterizing the permanent deformation behavior of soils. According to the evolution of axial strain (Werkmeister’s theory) or unit dissipated energy (Tao’s theory) with loading cycles, the behavior of unbound granular materials can be classified into three categories: plastic shakedown, plastic creep and incremental collapse. However, both theories are more suitable for the unbound granular materials with some limitations when used to separate the plastic creep and incremental collapse behavior. To overcome the limitations of the current theories, 26 cyclic triaxial tests were conducted on a saturated fully weathered red mudstone (SFWRM) to study the evolution of axial strain and unit dissipated energy during cyclic loading. A clear dependency of axial strain, axial strain rate on the unit dissipated energy level under various cyclic stress states were observed. A new criterion which is based on the responses of unit dissipated energy with cyclic stress ratio, was proposed to determine the limit between plastic creep and incremental collapse. Comparing with Werkmeister’s criterion and Tao’s criterion, the proposed criterion showed a better performance in identifying the incremental collapse behavior of the SFWRM.

WANG Long 1, 2, 3, CHEN Guoxing 2, HU Wei 3, SUN Dean 4, LI Jie 5, LIU Wenhua 1

The seismic excitation remains the main factor in triggering the slope failures that present three-dimensional (3D) features universally. The slopes combined with anti-slide piles are the effective reinforcement techniques in improving the slope stability and are widely employed in slope failure preventions. Based on the upper bound limit analysis theorem and the pseudo-dynamic approach, the plasticity deformation theory is extended to unsaturated soils, and a modified horizontal slice method is proposed to calculate the work rates of unsaturated soil gravity, seismic inertial forces and pile lateral resistance forces as well as the energy dissipation rate of apparent cohesion that are all characterized with nonlinear distribution features. The semi-analytical method is validated through comparisons with the analytical solutions. A series of parametric analyses are conducted regarding the seismic responses of unsaturated soil slopes. The improvements in seismic slope stability due to soil suction are studied systematically. The results show that the slope safety is underestimated by 15% ~ 30% when the soil suction is not considered in the analyses. The suction effects depend on the seismic excitations and are enhanced significantly when the seismic wave approaches the peak. The horizontal acceleration coefficient and soil shear modulus both have a great influence on the slope stability. The critical slip surface becomes much shallower under excitation conditions.

XU Tao 1, SHI Qingfeng 1, ZHANG Dingwen 1, XU Jingmin 1, LIU Yihuai 2

The slurry pressure can be transferred to the soil skeleton of the tunnel face through the filter cake and becomes the effective stress, which therefore is important for the tunnel face during slurry shield tunnelling. From the laboratory infiltration tests, three key factors affecting the formation of filter cake are discussed: the hydraulic gradient on the tunnel face, the sand content of slurry and the soil particle size. A lower hydraulic gradient leads to longer time of filter cake formation. A filter cake is more easily formed for the fine sand than the medium and coarse sand, but the filter cake is easily damaged. Although a filter cake is harder to be formed for the medium and coarse sand, the slurry-infiltrated zone is thicker and thus is more significant for the stability of the tunnel face. The permeability coefficient of the filter cake is more than 100 times lower than that of the slurry-infiltrated soil. The permeability coefficient of the filter cake is less than 10-8 m/s, while that of the slurry-infiltrated soil is between 10-7~10-5 m/s. A lower permeability coefficient of the filter cake or slurry-infiltrated zone leads to a smaller distribution zone and a higher decrease rate of the excess pore pressure. When the slurry is mixed with sand, the slurry infiltration rate is higher than that of the clean slurry. The permeability coefficient of the slurry-infiltrated zone increases with the increasing slurry density, and the decrease rate of the excess pore pressure decreases with the increasing slurry density.

Xiaoying Qiao, Meng Jiang, Shaoyang Ma

The interaction between lake water and groundwater is of great significance to the rational development and utilization of water resources. In this paper, based on temperature tracer principle, two methods including of the analytical method and numerical simulation method are used to comprehensively study the interaction between lake water and groundwater with a buried depth of 0-0.4 meters at the lake bed in the beach of Maowusu Lake Basin. In addition, compared with the result by hydrodynamic method. The results show that from May 20 to 28, 2018, the vertical seepage velocity between lake water and groundwater is 2×10-7-1×10-6 m/s, and the seepage velocity at the buried depth is 0.4 m is greater than that at the buried depth of 0.2 m. Precipitation have a certain impact on the results of analytic method, and there is a certain lag in the seepage velocity at the buried depth of 0.4 m. Without less rainfall interference, the results of numerical method and hydrodynamic method are of good agreement, furthermore the results of the three methods are in the same order of magnitude. At the same time, the volume heat capacity and porosity of lake bed sediments have great influence on the results. In the study of interaction between lake water and groundwater in semi-arid areas, numerical simulation is much better choice when the monitoring data are collected completely.

GAO Guo-yao 1, GUO Wei 1, ZHOU Feng-xi 2

The multi-field coupling problem of water, heat and salt in the composite unsaturated soils composed of unsaturated clay and unsaturated sand is studied. Based on the mass and energy conservation equations for porous media, the temperature, pore pressure, salt content and their gradients are selected as the state variables, and the state equations for the multi-field coupling problem of water, heat and salt under unsteady conditions are established. After the Laplace transformation of the state equations, the frequency-domain solution for the strongly coupled nonlinear variable coefficient differential equations is solved, and the time-domain solution is obtained by the inversion method. The numerical solution is compared with the experimental results of the self-designed tests, and the accuracy of the established mathematical model is verified. The influences of the thickness and saturated permeability coefficient of the unsaturated sand at the bottom of the composite unsaturated soils on the distribution and migration law of water and salt fields in the whole unsaturated soils under the temperature gradient are analyzed, and then the test and theoretical basis are provided for the improvement of saline soils and the construction of engineering soil barriers.

Deliang Wang, Lianfu Mei

The Aure fold-thrust belt is an important area for oil and gas exploration in Papua New Guinea, but the structural deformation and evolution of the fold-thrust belt are not well understood.In this paper, 2D and 3D seismic data, drilling and geological data covering the structural belt, combined with previous geological research results, were used to identify the structure and kinematics characteristics of the Aure fold-thrust belt.Guided by the theory of fault-related folds, the seismic data are interpretation.The Aure fold-thrust belt can be divided into three sections along the strike, and the structural deformation of the belt has obvious differences, which are mainly reflected in the following aspects: ①In the trend from NE to SW, the deformation level is gradually shallow, the involved strata are gradually new, and the deformation degree is gradually weaker; ②Along the strike from NW to SE, the extension range becomes smaller, the foreland sedimentary strata become newer, the tectonic deformation time becomes later, the shortening rate becomes larger, and the shortening amount becomes smaller; ③The western section and the middle section are disintegrated vertically, and the eastern section is inherited deformation.The results can provide basin evidence for oil and gas exploration in Papua New Guinea and regional tectonic evolution in the northern margin of Australia.

Zhenwei Guo, J. Lai, Ke-neng Zhang et al.

Ong Siong Guan, Raoof Gholami, Arshad Raza et al.

There have been many attempts to improve the filtration control of water based muds under High Pressure High Temperature (HPHT) condition using a cost effective approach. Nano particles are perhaps the best option considering their successful applications reported in many studies. However, they are often expensive and pose unfavourably changes on the rheology of the muds. In this paper, an attempt was made to show the application of Nano Glass Flakes (NGFs) as a cheap but effective nano particle to control the filtration of water based muds under HPHT conditions. Performing a series of rheology, filtration and conductivity tests on the mud samples with unmodified NGFs revealed that this nano particle increases the mud rheology, yield point and gel strength of the mud with a slight impact on the filtration loss. However, by modifying the surface charges of NGFs with a cationic surfactant, filtration loss was significantly reduced without any severe impacts on the mud rheology. Considering the conductivity of the mud which increases by adding the modified NGF, this nano particle might be a good choice to improve the overall performance of water based muds under HPHT conditions. Keywords: Nano glass flakes, Filtration loss, Rheology, HPHT, Dispersion

Sina Lohrasb, Radzuan Junin

Acidizing treatment is considered as a significant process in the oil well stimulations to form wormholes in carbonate formation in order to enhance the reservoir fluid production. Obtaining the number of pore volumes to breakthrough is an important objective in matrix acidizing, for it contributes to determining the wormhole characteristics such as type, shape, and size. Finding this number in experimental works requires a considerable amount of time, energy and cost. Therefore, this study aimed to establish an analytical method in which a reasonable result is achieved for the number of pore volumes to breakthrough. This purpose is accomplished by solely implementing acid and formation properties without performing any experimental works. The process of wormhole creation is done through developing a numerical model by utilizing the conservation of mass law method in which the carbonate core is considered as a closed system and the overall mass in the system as constant during the acid injection process. Furthermore, a constant number is added to the mathematical part of the model in order to eliminate the dimensionless Damköhler number which is supposed to be calculated experimentally. The results of the numerical procedure of the model are further compared to four other experimental works, which led to calculating the average accuracy of this model that is shown to be 95.98%. This study puts forward a comprehensive numerical model to estimate the number of pore volumes to breakthrough with an acceptable accuracy rate merely through implementing known acid and core properties.

Abhishek Rawat, Linzhi Lang, Wiebke Baille et al.

A methodology for identifying and calibrating the material parameters for a coupled hydro-mechanical problem is presented in this paper. For validation purpose, a laboratory-based water infiltration test was numerically simulated using finite element method (FEM). The test was conducted using a self-designed column-type experimental device, which mimicked the wetting process of a candidate backfill material in a nuclear waste repository. The real-time measurements of key state variables (e.g. water content, relative humidity, temperature, and total stresses) were performed with the monitoring sensors along the height of cylindrical soil sample. For numerical simulation, the modified Barcelona Basic Model (BBM) along with soil-water retention model for compacted bentonite was used. It shows that the identified model parameters successfully captured the moisture migration process under an applied hydraulic gradient in a bentonite-based compacted soil sample. A comparison between the measured and predicted values of total stresses both in axial and lateral directions along with other state variables revealed that heterogeneous moisture content was distributed along the hydration-path, resulting in non-uniform stress-deformation characteristics of soil.

P. Sreelakshmi, T. Mathew, K. Umamaheswaran et al.

Liu Bo, Yang Weihong

It is difficult to consider the change of settlement along with time by using stochastic medium theory in the settlement prediction process in subway construction. A new settlement-time model is proposed. This model is based on normally distributed cumulative function. A prediction model of three-dimensional ground surface settlement considering time effect induced by subway tunneling is built up by using stochastic medium theory. The prediction formulae of ground surface settlement considering time effect induced by single tunnel and twin tunnels are deduced. The computing method of three-dimensional incline and curvature of the ground surface settlement considering time effect is presented. A case study of back analysis is presented based on the Dougezhuang-Heizhuanghu section tunnel project of Beijing subway construction. The results show that:The time-settlement model is close to the measured data,which proved the model is scientific; The model can make prediction of the spatial distribution and time variation of settlement; According by the predicted settlement surface,we can calculate the three-dimensional incline and curvature of the ground surface settlement,and obtain the differential settlement and shape of the surface settlement over time.

В основу проведенного палеобатиметрического моделирования положена специфика расселения бентосных фораминифер в среднеюрском-раннемеловом бассейне на северо-востоке Ульяновско-Саратовского прогиба (восток Русской плиты). Прослежена динамика изменения родового и видового состава известкового и агглютинирующего сообщества, появления новых видов, общей численности популяции фораминифер. Построены графики изменения данных параметров по средне-верхнеюрской и нижнемеловой части разреза с разбивкой на батиметрические зоны. Батиметрические кривые характеризуют вариации палеоглубин бассейна для каждой из четырех выделенных в разрезе секвенций: батской-среднекелловейской, верхнекиммериджской-верхневолжской, верхнеготеривской-среднеаптской и среднеальбской. Пиковые значения всплесков биоразнообразия и численности фораминифер маркируют поверхности максимумов трансгрессий, разделяющие трансгрессивные системные тракты и тракты высокого стояния.