Soft Rock Strata Research Articles

A Field Study to Measure the Surrounding Stress of Rock and Supporting Structure of a Steep Tunnel with a Combination of Hard and Soft Rock Layers under Plate Compression

Tunnels excavated in a combination of hard and soft rock strata with high ground stress are prone to large deformations, collapse, and other disasters. The Yongfeng Tunnel, a reconstruction and expansion of the G544 line, suffered severe high ground stress from plate compression. This paper studied the surrounding rock pressure and supporting structure stress characteristics of tunnels with a combination of hard and soft rock strata with high ground stress by using earth pressure cells, surface strain gauges, and embedded strain gauges to test all stress related to the surrounding rock, primary support, and secondary lining. It was found that the contact pressure (P1) between the initial support and the surrounding rock and the contact pressure (P2) between the initial support of the leading tunnel were distributed in the direction of vertical stratification, while the contact pressures (P1 and P2) of the lagging tunnel were different due to the excavation unloading of the leading tunnel. The maximum stress positions of the initial support of the leading tunnel and the lagging tunnel were located in the left arch waist and the vault, respectively. However, the maximum stress position of the secondary lining was generally located on the side wall. The research results presented herein can guide future tunnel construction projects.

Seepage Actions and Their Consequences on the Support Scheme of Deep-Buried Tunnels Constructed in Soft Rock Strata

The stability of deep soft rock tunnels under seepage conditions is of particular concern. Aiming at thoroughly discussing seepage actions and their consequences on the support schemes of such structures, the host rocks of the Weilai Tunnel situated in the Guangxi province of China are used as the research subject. Emphasis is placed on adequately examining the seepage conditions, stresses, displacements and plastic zone radii along the surrounding rocks of such tunnels, taking into consideration the Mogi–Coulomb strength criterion and the elastic-plastic theory. Explicitly, this article proposes analytical solutions for stresses, displacements and plastic radii around deep tunnels in soft rocks under seepage conditions by considering the aforesaid criterion and nonlinear elastoplastic approaches. Subsequently, based on the strain-softening model, the coupled actions of seepage and softening on the rocks surrounding the tunnel are studied. In order to investigate the effects of relevant influencing factors on tunnel stability, parametric studies are thoroughly examined. According to the results, it is revealed that the support scheme of deep soft rock tunnels must be of the highest resistance possible to better decrease the plastic zone and the tangential stress along the host rocks. Moreover, throughout the surrounding rocks, the dissemination of pore water pressure is strongly affected by the uneven permeability coefficient under anisotropic seepage states. The combined effects of softening and seepage are very dangerous for the surrounding rocks of deep-buried tunnels. It is also shown that the seepage pressure substantially affects the plastic radii and tunnel displacements. Under high seepage pressure, the surface displacements of the tunnel are excessive, easily exceeding 400 mm. To better guarantee the reasonable longevity of such tunnels, the long-term monitoring of their support structures with reliable remote sensors is strongly recommended.

Insights into the breaking mechanism and fragment pattern of soft rock assisted by free face under TBM wedge cutter indentation

As an innovative and efficient rock breaking method, free face-assisted rock breaking is usually applied to tunnel excavation with TBM multi-stage cutterhead. To reveal the free face-assisted breaking mechanism of soft rock, the finite-discrete element method (FDEM) is adopted to study the mudstone fragmentation characteristics, cutter force, acoustic emission (AE) and rock breaking efficiency. Then, the numerical tests of mudstone samples with different free face conditions under TBM cutter indentation are conducted. The variations of fragmentation pattern, rock breaking angle and maximum cutter force with free face spacing and height are analyzed. Finally, a fragment extraction algorithm is used to identify rock fragment distribution. The fragment area, cutter work and specific energy (SE) are calculated. Results show that free face-assisted fragmentation has a higher rock breaking efficiency with more complete and larger-area fragments compared with traditional breaking method. There are three rock fragmentation patterns controlled by several critical values of free face spacing and height. Besides, a spacing of 75 mm and a height of 125 mm can bring the largest fragment area and the highest rock breaking efficiency. The results can provide theoretical guidance for the design of TBM multi-stage cutterhead for efficient tunneling in soft rock strata.

Research on gob‐side entry‐retaining technology with coal rib and corner strengthened support in soft rock strata

AbstractThe gob‐side entry‐retaining by roof cutting and pressure relief (GERRC) method is an advanced no‐pillar mining method that can significantly improve coal recovery and reduce roadway accidents. However, according to case studies, there is relatively little research on the application of the GERRC method in geological conditions of soft rock formations (especially when the roof and floor are both mudstone), and such research is needed. Therefore, based on the typical soft strata of the Xinyi Coal Mine, this paper analyzes the failure mechanism of the roadways and proposes the GERRC method with coal rib and corner strengthened support (CRCSS). The evaluation indexes of the roof convergence rate and cable safety margin are established, and the effects of roof cutting and CRCSS on roadway deformation control are explored by a numerical comparison test. The results show that roof cutting has a limited effect on roadway deformation. The deformation can be reduced by 75.77% by implementing CRCSS on the basis of GERRC. Then, the evolution characteristics of roadway stress and deformation in the process of mining are further discussed through field contrast tests. The field application results show that compared with that of GERRC with conventional support, the surrounding rock deformation of GERRC with CRCSS is reduced by more than 55%, the safety margin of the cable is improved. The overpressure of the hydraulic prop is diminished, and the stability distance of the roadway is reduced by approximately 30%. Finally, this paper discusses the mechanism to control roadway deformation by CRCSS. This research expounds the rationality of CRCSS, and the results can provide a reference for other situations with similar geological conditions.

Key factors in hole-sealing and pressure-relief failure of hydraulic fracturing straddle packer in coal mine

Hydraulic fracturing technology is widely used in coal mines, and straddle packers are a key component of this technology. However, during the application of a straddle packer, potential problems occur, including hole-sealing failure and shooting rod events at the pressure-relief stage, which may result in serious harm to on-site personnel. Therefore, we here investigated the application of straddle packers in five coal mines. The failure type, rock layer in which failure occurred, and frequency of use of straddle packers were analyzed. The most common failure type was packer capsule rupture, and this mostly occurred in sandstone and mudstone strata. The frequency of use was directly related to the rock stratum structure, while hole-sealing failure occurred most easily near to rock stratum interfaces. Analysis of the mechanical behavior of straddle packer hole-sealing failure showed that soft rock strata and capsule rupture were the key factors leading to such failures. Hard and stable rock formations, appropriate expansion of the diameter of boreholes, and strict manufacturing quality control can play important roles in preventing hole-sealing failures of straddle packers. Residual high-pressure water in the packer section or upper part of the straddle packer was the key factor causing pressure-relief failure and shooting rod events; to prevent these issues, high-pressure water should be fully released, anti-channeling chains should be used, and existing straddle packer technology should be optimized.

Settlement Prediction Method of Extra-Large Diameter Tunnels in Soft Rock Strata

This research was undertaken to predict the result of vault settlement during the excavation of super-large-span tunnels in soft rock strata, which are prone to deformation and hard to predict aftermaths. Numerical simulation was applied to tackle with vault problems during excavation of super-large-span soft rock tunnels such as proneness to deformation and hard prediction on vault settlement. As a result, a model for continuous prediction of vault settlement as the tunnel face keeps advancing was proposed, with influencing factors such as excavation span and tunnel depth taken into consideration, and put forward the optimization of super-large-span variable-section tunnels construction scheme. The results show that the vault settlement becomes fast at the beginning of the excavation because its surrounding rocks are characterized by weakness, incompleteness, and poor stability. At the initial stage of excavation, the varying tunnel depth had a greater impact on vault settlement, indicating that the primary support has to be enhanced at the beginning of the excavation of a vault with weak surrounding rocks. As the excavation of pilot tunnels proceeds, the high-stress zone transfers to the deep part of the surrounding rocks. The tunnel vault settlement model is capable of rapidly predicting the vault settlement at locations other than the observation points. The final settlement amount is affected by the excavation span, the tunnel depth, and the basic mechanical parameters of surrounding rocks. The key to the construction of a super-large-span and variable cross-section tunnel lies in the cross-section varying parts where the stress is concentrated, thus requiring reinforcement and frequent monitoring. The research methods and analysis may provide basic data and technical means for the control of the vault settlement of large-span tunnels in soft rock strata.

Seismic response and damage mechanism of tunnel lining in sensitive environment of soft rock stratum

Abstract In order to investigate the dynamic response characteristics and damage mechanism of the tunnel lining at the tunnel portal in the bridge–tunnel overlapping section in soft rock strata, a physical model with the scale ratio of 1:50 was made based on the similarity theory for shaking table tests. The acceleration and strain results of the tunnel lining under EL Centro seismic waves with different acceleration peak values were studied. Test results show that most of the acceleration values have significant amplification effects compared to input seismic waves, which increased significantly with greater peak values and elevations. Tensile deformations appear along the longitudinal and the circumferential directions of the tunnel lining. The tunnel spandrel and tunnel vault are the maximum deformation parts, respectively, at the standard section and the enlarged section of the tunnel lining. Therefore, it is suggested that the longitudinal anti-tensile design of the tunnel lining at the tunnel portal in such sensitive environments should be strengthened. And the anti-seismic design standard and durability requirement of the standard section of the tunnel lining adjacent to the enlarged section should be improved, so as to meet the requirements for stress deformation and overall stability when subjected to severe earthquakes.

Stability analysis of soft–hard-interbedded anti-inclined rock slope

The instability of rock slope is still a very frequent geological disaster, which seriously affects people's life and production activities. Previous studies have mainly focused on deformation mechanism, prediction, and control of hard rock with single lithology, while there are limited studies on the theoretic computational method of the stability for soft–hard interbedded anti-inclined rock strata. In this study, a geomechanical model for the toppling failure of soft–hard-interbedded anti-inclined rock slope is established. The modes of failure for soft and hard rock strata are analyzed, the computational formula of the downward thrust for each anti-inclined rock stratum is derived, and the stability safety factor of each rock stratum is defined. A theoretical computational method for determining the potentially most dangerous failure surface of soft–hard-interbedded anti-inclined rock slope is proposed. By comparing with the existing research results, the theoretical solving method proposed in this study can well solve the location of the potentially most dangerous failure surface of soft–hard-interbedded anti-inclined rock slope. The potentially most dangerous failure surface of this kind of slope is approximately planar, and the angle between it and the normal plane of the rock strata is an acute angle within 30°. It provides theoretical support for the stability analysis of this kind of slope.

Peridynamic investigation on crack propagation mechanism of rock mass during excavation of tunnel group in cold regions

An extended ordinary state-based peridynamic model was developed to investigate the crack propagation of surrounding rock due to tunnel excavation. The frost heave effect on the crack surface was described by an equivalent pressure density. Two numerical examples were conducted to verify the effectiveness and robustness of the proposed model. Moreover, the influence of frost heave pressure, buried depth and rock elastic modulus on damage characteristics of the surrounding rock was investigated. The results demonstrate that massive microcrack damage will be formed at the invert when the tunnel is excavated in a deeply buried rock mass or soft rock stratum. HIGHLIGHTS A peridynamic model of rock mass under excavation and frost heave was constructed. Damage characteristics of surrounding rock could be simulated efficiently. Frost heave load was exerted on the crack surface by an equivalent pressure density. The effects of frost heave load, buried depth and rock elastic modulus were studied.

Study on Blasting Characteristics of Soft-Hard Rock Strata Based on Energy Fields and Particle Expansion Loading Algorithm

Complex geological conditions often make the blasting effect difficult to control. In order to explore the influence of soft-hard rock strata on rock blasting characteristics, based on PFC2D software, combined with particle expansion loading algorithm, the numerical simulation blasting experiments are carried out. Firstly, the rationality of blasting method is verified by single-hole sandstone blasting experiment. Then, the soft-hard composite strata are established, and the single-hole blasting experiments of composite strata, with different distribution thickness of soft rock stratum and hard rock stratum, are carried out. The experimental results are analyzed from three perspectives: crack network state, internal stress of rock mass, and energy field. Results show that (i) the distance between the interface of soft-hard rock and the blasthole seriously affects the blasting effect. The law of crack number varying with the distance is obtained through further analysis. (ii) When detonated in the hard rock, if the structural plane is about 2 times the radius of crushing area from blasthole, the rock mass will be in a relatively high stress state due to the reflection and superposition of stress waves. (iii) When detonated in the hard rock, if the structural plane is about 2 times the radius of crushing area from blasthole, compared with pure hard rock case, the peak kinetic energy and peak friction energy are increased by about 15 times and 2.6 times, respectively, and the peak strain energy is attenuated by 18%.

Experimental study on the progressive failure behaviour of shallow tunnel-type anchorage in soft-rock strata using digital image correlation

The instability of shallow tunnel-type anchorages (TTAs) installed in soft-rock strata is a progressive process; however, these have not been completely investigated. Hence, in this study, the pullout behaviours and crack-propagation characteristics of TTAs are investigated using the digital image correlation (DIC) technique. Digital images of the anchorage are captured during an experiment and are processed using the DIC to obtain the surrounding-rock deformation fields. Subsequently, the TTA pullout performance and the mechanical response of surrounding rock are analysed, and propagation of cracks in different load-bearing stages of the TTA are investigated. The results show that TTA failure gradually changed from single failure of rock mass to dual failure of rock mass and interface slip and debonding. Losing of bearing capacity of TTAs is caused by the continuous propagation of cracks, leading to the weakening of the clamping effect of rock mass and deteriorating of the shear capacity of interface.

Analysis and Intelligent Prediction for Displacement of Stratum and Tunnel Lining by Shield Tunnel Excavation in Complex Geological Conditions: A Case Study

This paper presents the analysis and intelligent prediction for the displacement of stratum and tunnel lining of Qingdao Metro Line 4 by earth pressure balance (EPB) shield tunnel excavation in complex strata. When the tunnel is excavated in different stratum sections, the tunneling parameters of shield machine are systematically analyzed and compared, and the vertical displacement of the tunnel crown and the horizontal convergence deformation on both sides are investigated. When the tunnel body passes through the soft soil stratum and rock stratum, the curves of the vertical displacement of the stratum surface with time are respectively discussed. A machine learning method for predicting stratum surface deformation induced by shield tunnel excavation in complex strata is developed, where extreme learning machine (ELM), particle swarm optimization (PSO) algorithm and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -fold cross-validation method are comprehensively considered. 65 data samples are collected from the field monitoring data of Qingdao Metro Line 4 and each data sample includes seven input values and one output value. The developed PSO-ELM has good prediction performance for stratum surface vertical displacement due to shield tunnel excavation. The case study in this work can provide a practical reference for similar tunneling projects.

Failure mechanism and support system of roofs in advance areas affected by mining under the condition of soft rock stratum

The advance area affected by mining (AAAM) of the Lijiahao coal mine is influenced by the superposition of the side and advance abutment pressure, and the roadway roof is considerably damaged. General support technology and equipment cannot economically and effectively maintain the stability of the roadway roof of AAAM. Through field detection, theoretical analysis, and numerical simulation, this study analyzes the structure of the surrounding rock, the evolution characteristics of the regional stress field, the distribution of the surrounding rock plastic zone, and the influencing factors of the plastic zone in the AAAM of the Lijiahao mine. The results show the following: 1) the direct roof and floor of the roadway comprise coal, siltstone, and sandy mudstone, which has low strength and can be easily broken. 2) The maximum and minimum principal stresses in the AAAM reach 2.3 and 1.5 times of in situ stress, respectively, and the ratio of the two stresses reaches 2–8, which causes the shape of the plastic zone of the surrounding rock to turn into a butterfly shape. 3) The principal stress direction of AAAM deflects at a large angle, which causes the deepest failure direction of the surrounding rock to rotate to the roof and floor of the roadway. Accordingly, a self-moving foldable support system is proposed to support the AAAM of the Lijiahao coal mine. The system will not support the roof repeatedly and is suitable for soft rock stratum. In addition, it can also adapt to the heave of roadway floor and avoid dumping. The mechanized operation of the system makes the roof support in AAAM more efficient and safer.

Green's functions based on the Timoshenko beam model for the longitudinal seismic dynamic response of tunnels crossing soft and hard rock strata

Weathered rocks typically exist in the portal section of mountain tunnels where the tunnels in the portal section often cross soft and hard rock strata. The interface between the soft and hard rocks is the control point in the seismic design of tunnels. However, there is currently no seismic design method based on dynamic methods that consider tunnels crossing soft and hard rock strata along their longitudinal direction. In this study, two elastic foundation beams in different rock strata were used to model the behaviour of a tunnel crossing soft and hard rock strata. Based on the Timoshenko beam vibration response theory, the higher-order differentials of the beam dynamic governing equation are transformed into algebraic equations using the Laplace transform. The closed-form solution of the dynamic response of the entire beam is derived by combining the boundary and deformation coordination conditions of two elastic foundation beams. Subsequently, the dynamic response of any point along the longitudinal direction of the elastic foundation beam (tunnel) crossing the soft and hard rock strata was obtained using Green's function. The validity of the method was verified by comparing it with a finite difference model. Finally, a parametric analysis was performed based on the analytical method derived in this study to investigate the influences of parameters such as the liner elastic modulus, liner thickness, modulus of elasticity ratio of hard rock to soft rock, and axial forces, on the seismic response of tunnels crossing soft and hard rock strata. The results suggest that with an increase in lining thickness, the bending moment and shear force of the tunnel become increasingly significant, but the transverse displacement response of the tunnel was slightly affected. With an increase in the elastic modulus of the lining, the difference in the peak values of the bending moment and shear force increases, whereas the transverse displacement response is slightly diminished. With an increase in the elastic modulus ratio of hard rock to soft rock, the difference in the peak values of the bending moment, shear force, and transverse displacement of the tunnel, varied more along the tunnel axis. With the increase in the axial force, the seismic responses from the bending moment and shear force on the tunnel cross-section were significantly weakened.

Seismic Responses and Damage Mechanisms of Deep-Buried Underground Powerhouse in Layered Rock Mass

Layered rock mass generally has adverse effects on the seismic stability of deep-buried underground powerhouses. Aiming at the complexity of seismic wave field in deep-buried underground powerhouses, the obliquely input methods of P and SV waves considering the incident direction and multi-incident surfaces are constructed in this study, respectively. It can convert the seismic wave input problem into the problem of solving equivalent nodal force acting on the artificial boundaries. Based on the characteristics of dynamic interaction between interlayers in layered rock mass, an explicit dynamic contact force method considering the seismic deterioration effect and bond-slip characteristics of interface is also presented to simulate various contact states such as bond, separation, and sliding. The combined application of the above methods to analyze the seismic response of underground powerhouse at Azad Pattan hydropower station shows that they could accurately simulate the seismic damage evolution process of deep-buried underground powerhouses in layered rock mass. The numerical results indicate that the obliquely incident seismic waves contribute to a larger seismic reaction of underground powerhouses, which largely lies in the amplitudes of the displacement and stress fluctuations. After considering the dynamic contact, the obvious seismic deterioration effect and interlaminar dislocation displacement occur between soft and hard rock, and the sidewalls suffer more severe deterioration degree than the top arch. The seismic damage area of lining structure is mainly distributed in the place where the soft rock strata pass through and the upper structure with larger free surface. Additionally, two major damage modes of underground powerhouses in layered rock mass, namely, damage due to structural deformation and interlaminar dislocation, are derived from the numerical results and can be reasonably explained by the corresponding damage mechanisms.

Deformation Prediction of Tunnel-Surrounding Rock Considering the Time Effect of the Viscosity Coefficient: A Case of an NATM-Excavated Tunnel

Considering engineering problems such as complicated stress and the difficulty in controlling large deformation while a tunnel passes through a soft rock stratum, a theoretical prediction model of convergence deformation of tunnel-surrounding rock is proposed. Based on the longitudinal displacement profile curve reflecting the “space effect” of the excavation surface, the Hoek formula with better applicability was introduced to analyze and theoretically deduct the “time–space effect comprehensively.” By taking the influence of the “time effect” coefficient into account, an improved Nishihara model was established to derive the analytical equation of the viscoelastic–viscoplastic convergence of surrounding rock. Taking the Dingxi Tunnel of Wujing Expressway in Hunan Province, the physical and mechanical parameters of surrounding rock in the tunnel were firstly determined then they were used to calculate and predict the vault down of three typical sections with the scoping equation of surrounding rock deformation. Based on the calculation results, the causes of the differences between the measured and theoretical values were analyzed; moreover, it is indicated that the minimum root-mean-square error is 1.68, the minimum average error is 1.3%, and the correlation coefficient is 0.99. The comparison shows that the theoretical prediction results agree well with the corresponding field test results. The improved Nishihara model can accurately predict the final deformation of the surrounding rock. Simultaneously, it is also proved that the relevant parameters and the hypothesis and correlation of the nonlinear viscosity coefficient equation are reasonable, with particular effectiveness and applicability in practical engineering. This study is significant for further studying the tunnel-surrounding rock’s stability and accumulating theoretical and practical experience to develop rheological theory.

Research and Control of Underground Pressure Law of Coal Mining Face in Soft Rock Strata Based on Neural Network under the Background of Wireless Network Communication

Our country has a vast territory and rich resources, but it is a country with more coal, less oil, and poor gas. With the increase of our population, the development of society, and the more severe international situation, coal has become more important for our country’s economic development and energy. Security plays an irreplaceable role. Based on the neural network, this paper studies and controls the underground pressure law of the coal mine’s soft rock heading face, aiming at the safe and efficient mining of the first face and providing an experience for the next face. This paper mainly uses BP neural network learning algorithm and support pressure algorithm to measure and study the ground pressure law of coal mine soft rock heading face and establishes the ground pressure online monitoring system, which is used to analyze and summarize the ground pressure abnormal area during the mining of the working face, so as to provide the basis for safe mining of the working face. Through the field measured data, the initial pressure step and periodic pressure step at the upper, middle, and lower parts of the working face, the average working resistance of the support at the working face during pressure, and the dynamic load coefficient of the support are obtained. It is analyzed that the support in the middle of the working face has a large load and the pressure is obvious. The experimental results show that the initial support force of the whole working face is approximately normally distributed, the proportion of the initial support force in the range of 10–30 MPa accounts for more than 85% of the total statistics, and the frequency of the initial support force in the upper, middle, and lower stations at 10–25 MPa is 55%–65%.

Detection of a Weak Structural Stratum and Stability Analysis of the Slope in an Intensely Weathered Open-pit Mine

Within the mining boundary of an open-pit mine located in southern China, due to the intense weathering of the slope rock stratum, the quaternary loose soil layer and soft rock stratum, karst cavity and water-bearing weathered-fracture zone and other weak structural strata have posed a great threat to the side slope stability of open-pit mining. Using the Flashres64 Multichannel Ultra-High-Density Electrometer to conduct on-site detection of the slope, based on the spatial distribution of the low-resistance layer and the drilling geological data, this study interpreted the stratum lithology of the slope and conducted effective identification of the weak structural stratum. Furthermore, according to the Hoek–Brown Failure Criterion, the Flashres64 reduced the strength of the mechanical parameters of the rock-soil and weak structural stratum of the slope, and imported the relevant data into the SLIDE software for slope stability analysis. The results showed that this method could make advanced macro–predictions of the weak structural stratum occurring in intensely weathered slopes. The slope stability analysis results considering the adverse effects of the weak structural stratum were also highly consistent with the actual engineering situation, for which the application is worth promoting in related fields.

Viscoelastoplastic Displacement Solution for Deep Buried Circular Tunnel Based on a Fractional Derivative Creep Model

Time-dependent deformation of surrounding rock is a common phenomenon for tunnels situated in soft rock stratum or hard rock stratum with high geo-stress. To describe this phenomenon, a creep model combining the Abel dashpot and a non-Newton viscous element was adopted, and the analytical solution about the viscoelastoplastic deformation for circular tunnel was obtained based on this creep model. Then, the auxiliary tunnel of Jinping II hydropower station was taken as an example to reveal the influence of creep parameters on the creep deformation. The research shows that (1) the creep model can well describe the whole creep stage of rocks, that is, the decay, constant, and accelerated creep stages, (2) the creep deformation has a positive relation with the value of fractional order of Abel dashpot and the order of the non-Newton viscous element, and (3) the creep curves between test results and analytical solutions are well consistent with each other, which demonstrate the validity of the analytical solution.

Application of Modified Hoek–Brown Strength Criterion in Water-Rich Soft Rock Tunnel

When a tunnel is excavated in the water-rich soft rock stratum, the strength of the soft rock is greatly reduced due to the seepage of groundwater. The condition may result in engineering accidents, such as large deformation, limit invasion, and even local collapse of the tunnel. Therefore, it is very important to research the stability of the surrounding rock in the water-rich soft rock tunnel. The water-rich disturbance factor considering the seepage influence of groundwater and blasting disturbance is proposed, and the generalized Hoek–Brown strength criterion is modified on the basis of the immersion softening test of soft rock. In accordance with the classical elastic–plastic mechanics theory, the stress, strain, and displacement calculation formulas of the tunnel surrounding rock are derived. The displacement of tunnel surrounding rock is analyzed using the derived formula and the modified Hoek–Brown strength criterion and then compared with the measured value. Results show that the displacement of surrounding rock, which is calculated by modified Hoek–Brown strength criterion considering water-rich disturbance factor and the displacement calculation formula, is close to the measured deformation of surrounding rock in water-rich soft rock tunnel, and the error is small. Therefore, the modified Hoek–Brown strength criterion can be applied to the water-rich soft rock tunnel, and the derived displacement calculation formula can accurately calculate the deformation of tunnel surrounding rock. It is of great significance to the study of surrounding rock stability of water-rich soft rock tunnel.