scholarly journals An Experimental and Numerical Investigation on the Initiation and Interaction of Double Cracks in Rocks under Hydromechanical Coupling

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jie Mei ◽  
Wanzhi Zhang
Keyword(s):  
Water Pressure ◽  
Critical Length ◽  
Maximum Energy ◽  
Enhancement Effect ◽  
Hydromechanical Coupling ◽  
Underground Engineering ◽  
Side Rock ◽  
Crack Tips ◽  
Dip Angle ◽  
Interaction Behaviors

The growth of double cracks is the main factor leading to progressive rock failure under hydromechanical coupling. The initiation modes and interaction behaviors of double cracks were investigated by using laboratory tests, and the influences of water pressure were analyzed. The maximum energy release rate criterion was modified to determine the crack growth characteristics. A numerical model was established and then verified by the test results. Based on the simulation, the distribution of stress fields and key fracture parameters of double cracks was investigated. Then, initiation characteristics and interaction behaviors of parallel and nonparallel cracks were quantitatively analyzed. The results indicate that the increase in water pressure leads to the crack initiation being inclined to the original surfaces and the growth length along the crack fronts tending to be uniform; the small tensile stress zones are formed close to the crack tips, and significant compressive stress zones are formed at both sides of the crack surfaces; stress superposition and interaction occur when crack spacing is less than 2.5a; the interactive weakening effect is mainly present in the inner side (rock bridge zone) of cracks, while a certain degree of interactive enhancement effect exhibits in the outer sides; the cracks are much easier to initiate at the outer wing cracks when the spacing is less than the critical length (0.5a); and cracks with a dip angle of 45° are much easier to initiate at the endpoints of long axis. The research results provide certain theoretical guidance for the safety assessment of underground engineering.

Developing an in situ, hydromechanical coupling, true triaxial rock compression tester and investigating the deformation patterns of reservoir bank slopes

2021 ◽  
pp. qjegh2021-043
Author(s):  
Lei Fan ◽  
Meiwan Yu ◽  
Aiqing Wu ◽  
Yihu Zhang
Keyword(s):  
Coupling Effect ◽  
Water Pressure ◽  
Pressure Coefficient ◽  
Hydromechanical Coupling ◽  
Rock Interaction ◽  
True Triaxial ◽  
Rock Structure ◽  
Deformation Patterns

Interactions between water and rocks are the main factors affecting the deformation of rock masses on sloped banks by reservoir impoundment. The technology used in laboratory tests of water-rock interaction mechanisms cannot simulate the coupling of water, the rock structure and the initial stress environment. In this work, we develop an in situ hydromechanical true triaxial rock compression tester and apply it to investigate the coupling response of reservoir bank rocks to changing groundwater levels. The tester is composed of a sealed chamber, loader, reactor, and device for measuring deformation, which are all capable of withstanding high water pressures, and a high-precision servo controller. The maximum axial load, lateral load and water pressure are 12 000 kN, 3 000 kN and 3 MPa, respectively. The dimensions of the test specimens are 310 mm×310 mm×620 mm. The test specimens are grey-black basalts with well-developed cracks from the Xiluodu reservoir area. The results show that increasing water pressure promotes axial compression and lateral expansion, while decreasing water pressure causes axial expansion and lateral compression. A water pressure coefficient, K, is introduced as a measure of the hydromechanical coupling effect (expansion or compression) with changing groundwater level. A mechanical tester can be used to perform accurate field tests of the response of wet rocks to hydromechanical coupling. The test results provide new information about the deformation patterns of rock slopes in areas surrounding high dams and reservoirs.Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

scholarly journals Theoretical Modeling of Rock Breakage by Hydraulic and Mechanical Tool

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hongxiang Jiang ◽  
Changlong Du ◽  
Songyong Liu ◽  
Liping Wang
Keyword(s):  
Theoretical Model ◽  
Water Pressure ◽  
Rock Fracture ◽  
Superposition Principle ◽  
Specific Energy Consumption ◽  
Critical Length ◽  
Rock Fragmentation ◽  
Rock Breakage ◽  
Hydraulic Impact ◽  
Mechanical Tool

Rock breakage by coupled mechanical and hydraulic action has been developed over the past several decades, but theoretical study on rock fragmentation by mechanical tool with water pressure assistance was still lacking. The theoretical model of rock breakage by mechanical tool was developed based on the rock fracture mechanics and the solution of Boussinesq’s problem, and it could explain the process of rock fragmentation as well as predicating the peak reacting force. The theoretical model of rock breakage by coupled mechanical and hydraulic action was developed according to the superposition principle of intensity factors at the crack tip, and the reacting force of mechanical tool assisted by hydraulic action could be reduced obviously if the crack with a critical length could be produced by mechanical or hydraulic impact. The experimental results indicated that the peak reacting force could be reduced about 15% assisted by medium water pressure, and quick reduction of reacting force after peak value decreased the specific energy consumption of rock fragmentation by mechanical tool. The crack formation by mechanical or hydraulic impact was the prerequisite to improvement of the ability of combined breakage.

Plugging Performance Optimization Tests of Grouting Material for Sudden Water Inflow of Underground Engineering Construction

2011 ◽  
Vol 306-307 ◽  
pp. 722-726 ◽  
Author(s):  
Li Ping Li ◽  
Shu Cai Li ◽  
Jin Sheng Cui ◽  
Zhao Li
Keyword(s):  
Performance Optimization ◽  
Water Pressure ◽  
High Water ◽  
Water Inflow ◽  
Karst Area ◽  
Seepage Water ◽  
Underground Engineering ◽  
Grouting Material ◽  
New Type ◽  
Plugging Performance

Sudden water inflow is the typical geological hazard during the construction period of underground, especially for the karst area. According to a new type of polymer chemical grout material called Malisan, plugging performance optimization tests of different grouting material had been carried out, such as ordinary cement, superfine cement and special cement of HSC, the geo time, consolidating strength, anti-erosion property and comprehensive properties of grouting harnessing had been systematically analyzed and compared. Test results showed that the new type of polymer chemical grout material has the significant characteristics of controllable gel time, high consolidating strength, anti-scour performance, water swelling and extremely strong permeability, it is more effective than conventional grouting material for grouting harnessing of seepage, water spraying and water inflow with high water pressure, in addition, it is convenient for transportation, material configuration and process operation.

Study on Technique of Automatic and Continuous Monitoring Groundwater Level and its Application to Engineering

2012 ◽  
Vol 170-173 ◽  
pp. 2060-2065
Author(s):  
Chun Bao Xiong ◽  
Hai Tao Wang
Keyword(s):  
Groundwater Level ◽  
Continuous Monitoring ◽  
Serial Communication ◽  
Water Pressure ◽  
Pumping Test ◽  
Underground Engineering ◽  
Engineering Project ◽  
Engineering Construction ◽  
Level Change ◽  
Java Language

Pumping test is a common method to obtain the hydrogeology information for underground engineering construction, of which monitoring groundwater level is an important part. A system of automatic and continuous monitoring groundwater level was developed to meet the special requirements of pumping test. Considering the characteristics of groundwater level change in pumping test, the sensor of water pressure based on vibration string was used. For connecting the sensor and computer, serial communication protocols were programmed in JAVA language. The system was applied to an engineering project, and it achieved the satisfactory effects.

scholarly journals Universal poroelastic mechanism for hydraulic signals in biomimetic and natural branches

2017 ◽  
Vol 114 (42) ◽  
pp. 11034-11039 ◽  
Author(s):  
J.-F. Louf ◽  
G. Guéna ◽  
E. Badel ◽  
Y. Forterre
Keyword(s):  
Growth Response ◽  
Pressure Pulse ◽  
Vascular System ◽  
Water Pressure ◽  
Local Deformation ◽  
Physical Parameters ◽  
Hydromechanical Coupling ◽  
Long Distance ◽  
Whole Plant ◽  
Basic Features

Plants constantly undergo external mechanical loads such as wind or touch and respond to these stimuli by acclimating their growth processes. A fascinating feature of this mechanical-induced growth response is that it can occur rapidly and at long distance from the initial site of stimulation, suggesting the existence of a fast signal that propagates across the whole plant. The nature and origin of the signal is still not understood, but it has been recently suggested that it could be purely mechanical and originate from the coupling between the local deformation of the tissues (bending) and the water pressure in the plant vascular system. Here, we address the physical origin of this hydromechanical coupling using a biomimetic strategy. We designed soft artificial branches perforated with longitudinal liquid-filled channels that mimic the basic features of natural stems and branches. In response to bending, a strong overpressure is generated in the channels that varies quadratically with the bending curvature. A model based on a mechanism analogous to the ovalization of hollow tubes enables us to predict quantitatively this nonlinear poroelastic response and identify the key physical parameters that control the generation of the pressure pulse. Further experiments conducted on natural tree branches reveal the same phenomenology. Once rescaled by the model prediction, both the biomimetic and natural branches fall on the same master curve, enlightening the universality of our poroelastic mechanism for the generation of hydraulic signals in plants.

scholarly journals Stress Heterogeneity and Slip Weakening of Faults under Various Stress and Slip

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Longjun Dong ◽  
Qiaomu Luo
Keyword(s):  
Slip Surface ◽  
Water Pressure ◽  
High Stress ◽  
Local Stress ◽  
Seismic Source ◽  
High Water ◽  
Fault Slip ◽  
Underground Engineering ◽  
Finite Element Software ◽  
Stress Heterogeneity

The rock mass of deep underground engineering is in the complex geological environment of high stress, high temperature, and high water pressure. In the process of deep mining and underground space development, the fault-slip seismic source may cause engineering accidents with strong destructive capacity. An in-depth study of fault slip characteristics is very important in the engineering disaster prevention and control. In this paper, a slip model was established based on the finite element software ABAQUS. A total of 20 loading ways are set for various stress and slip, which include the possible slip conditions of fast slip, slow slip, and critical state. By comparing the simulation diagrams and collecting the data of representative grid elements on the loading surface and slip surface, the slip characteristics such as stress heterogeneity under different loads are analyzed. The results show that the increase of slip velocity will make the slip unstable, and the local stress and deformation will become irregular. The spatial stress heterogeneity and the resulting local high working rate will lead to the decrease of the friction strength and the slip weakening. These results can provide some useful suggestions for the research of seismic activities caused by fault slip.

scholarly journals Investigation of Concrete Base-Roadbed Surface Contact Variation-Induced Vibration Characteristics of Vehicle-Slab Track-Subgrade System considering Fluid-Solid Interaction

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Kai-Wen Liu ◽  
Fei Yue ◽  
Qian Su ◽  
Bao Liu ◽  
Pengfei Zhou
Keyword(s):  
Surface Layer ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Critical Length ◽  
Bottom Layer ◽  
Dynamic Responses ◽  
Continuous Contact ◽  
Slab Track ◽  
Fluid Solid Interaction

The excessive pumping of fines in saturated roadbed surface layer, which is induced by the fluid-solid interaction under dynamic loads from high-speed train, is a special form of high-speed railway subgrade defect reported recently. This can deteriorate the interface between nonballasted track structure bottom layer and roadbed surface layer and therefore lead to associated contact variation with the moving of trains. According to the dynamic Biot’s equations known as u-p formulation and the vehicle-track coupling dynamics theory, a vertical vehicle-slab track-subgrade coupling vibration model is developed to investigate the aforementioned contact variation-induced dynamic behavior of the whole system considering the fluid-solid interaction. Dynamic measurements from a field case study are adopted to verify the computation model proposed. Based on the numerical model validated, the effects of three contact variation statuses (continuous contact, vibrating contact, and contact loss) on dynamic responses of track subsystem and subgrade subsystem, such as dynamic pore-water pressure, vertical accelerations, and dynamic displacements both in time and frequency domains, are investigated. Also, a sensitivity analysis involving rail speeds and lengths of contact loss zone is performed, and the critical length of contact loss zone is suggested.

scholarly journals Research on Ground Liquefaction and Structural Force Characteristics of Underground Utility Tunnels Under CLC Stratigraphic Model

2021 ◽  
Author(s):  
Tian Tian ◽  
aijun Yao ◽  
Yifei Gong ◽  
Yaozhen Guo
Keyword(s):  
Pore Water Pressure ◽  
Numerical Study ◽  
Water Pressure ◽  
Volumetric Strain ◽  
Sine Wave ◽  
Burial Depth ◽  
Underground Structures ◽  
Underground Engineering ◽  
Stratigraphic Model ◽  
Structure Height

Abstract Damages to underground structures due to liquefaction of the soils caused by cyclic loads such as earthquakes have always been an important issue in geotechnical underground engineering practices. This paper presents a numerical study of the utility tunnels at different burial depths in "Coh-Liq-Coh" horizontally layered liquefiable grounds using the finite-difference program FLAC3D. "Finn-Byrne" cyclic load volumetric strain increment model simulates the fluid-solid coupling of saturated sand and the increase in pore water pressure during vibration. The numerical model was loaded using an acceleration sine wave for dynamic calculations. The numerical results showed that the burial depths have a strong influence on the liquefaction of the soil beneath the utility tunnels and on the forces and deformations of the structures. Under the numerical simulation conditions in this paper, the greater the burial depth, the greater the liquefaction of the soil beneath the structure, the greater the shear stress on the side walls and the smaller the settlement difference between the structure and the surrounding soil. In the numerical simulations in this paper, a reasonable burial depth for utility tunnels was 0.8 to 1.1 times of the structure height.

scholarly journals The Unsaturated Hydromechanical Coupling Model of Rock Slope Considering Rainfall Infiltration Using DDA

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Xianshan Liu ◽  
Ming Xu
Keyword(s):  
Water Flow ◽  
Rock Slope ◽  
Rainfall Intensity ◽  
Water Pressure ◽  
Great Influence ◽  
Coupling Model ◽  
Rainfall Infiltration ◽  
Discontinuous Deformation Analysis ◽  
Reservoir Rock ◽  
Hydromechanical Coupling

Water flow and hydromechanical coupling process in fractured rocks is more different from that in general porous media because of heterogeneous spatial fractures and possible fracture-dominated flow; a saturated-unsaturated hydromechanical coupling model using a discontinuous deformation analysis (DDA) similar to FEM and DEM was employed to analyze water movement in saturated-unsaturated deformed rocks, in which the Van-Genuchten model differently treated the rock and fractures permeable properties to describe the constitutive relationships. The calibrating results for the dam foundation indicated the validation and feasibility of the proposed model and are also in good agreement with the calculations based on DEM still demonstrating its superiority. And then, the rainfall infiltration in a reservoir rock slope was detailedly investigated to describe the water pressure on the fault surface and inside the rocks, displacement, and stress distribution under hydromechanical coupling conditions and uncoupling conditions. It was observed that greater rainfall intensity and longer rainfall time resulted in lower stability of the rock slope, and larger difference was very obvious between the hydromechanical coupling condition and uncoupling condition, demonstrating that rainfall intensity, rainfall time, and hydromechanical coupling effect had great influence on the saturated-unsaturated water flow behavior and mechanical response of the fractured rock slopes.

Influence of Stress and Water Pressure on the Permeability of Fissured Sandstone Under Hydromechanical Coupling

2018 ◽  
Vol 37 (4) ◽  
pp. 774-785 ◽  
Author(s):  
Shuai Zhang ◽  
Dongsheng Zhang ◽  
Zhen Wang ◽  
Mingwei Chen
Keyword(s):  
Water Pressure ◽  
Hydromechanical Coupling
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