Identifying seismic disaster precursors and instability early warning signs in tunnels is critical for seismic design and catastrophe warning. Current approaches predominantly rely on static assessments of specific states, either post-event or at peak response. Thus, they fail to capture the continuous evolution and abrupt transitions inherent in nonlinear dynamic systems. For this purpose, the Load/Unload Response Ratio (LURR) theory was introduced to evaluate the seismic stability of tunnels. Definitions were established for loading and unloading parameters, response parameters, and the LURR during the seismic response of tunnels. According to the principles of the LURR theory, shaking table model tests were performed on an unlined tunnel to study how the LURR varies and how the soil's stability changes with different seismic intensities. Research shows that as seismic amplitude increases, the stability of an unlined tunnel evolves through three distinct phases: stable bearing capacity, localized collapse, and overall collapse. A correlation is observed between the time-history curve of the LURR of the surrounding soil and the progression of stability. During the stable bearing phase, LURR values fluctuate at low magnitudes, while the maximum LURR at the weakest structural location (the arch foot) gradually rises with increasing seismic amplitude. As stability deteriorates, the LURR displays a localized growth pattern in the crown and sidewall regions (monitoring points 1-4). A declining trend in the regional LURR peak value corresponds to the onset of localized collapse in that specific area. Following the initial localized collapse, the maximum LURR shifts from the crown zone to the sidewall foot and invert waist areas. When the regional peak LURR in this secondary zone begins to decrease, the tunnel experiences overall collapse that propagates to the ground surface. Based on shaking table model test results, the decline of the first localized LURR peak, combined with its spatial migration, can serve as a criterion for assessing localized tunnel instability. Furthermore, the decline of two or more localized LURR peaks provides a predictive indicator for the overall instability of the tunnel.

This study evaluates the applicability of traditional vibration input methods in tunnel seismic analysis to address limited calculation accuracy and ambiguous applicability. The vibration input method, wave input method, and theoretical solutions are compared to clarify the error mechanism and main influencing factors. Through correlation analyses, the relationships between model dimensions, geological parameters, and accuracy are established. Then an innovative approach is proposed to improve the calculation accuracy and refine the scope of applicability. The results indicate that the assumed bedrock surface position and model boundaries can significantly affect the accuracy of the model, with the height and wave velocity of the surrounding rock being key control parameters. When the model height is fixed, the correlation coefficient between vibration and wave input results shows three stages of change with increasing width: rapid increase, deceleration growth, and asymptotic convergence to 1. In the case of a fixed width, as the height increases, the coefficient follows a trend of “approximately stable slightly decreasing”. The optimal aspect ratio is 1:2. Size optimization formulas under different rock conditions and methods for selecting analysis time periods are proposed to clarify the engineering applicability of the vibration input method.

Tunnels are highly susceptible to structural damage induced by active fault dislocations. Current engineering practice offers limited effective protection measures against large-magnitude fault displacements. To address this issue, this study proposes an off-wall lining system integrated with airbag technology for tunnels traversing active fault zones. The structural assembly consists of four main components: the outer lining, the airbags, the inner lining, and the abutments. The outer lining acts as the primary support, while the inner lining encloses the operational tunnel space. Circumferentially arranged airbag units occupy the annular gap between these structures. The abutments provide dedicated spaces for airbag maintenance and personnel access, while also enhancing structural stability. To evaluate the performance of this novel system under various configurations, three series of dislocation experiments were conducted using a self-designed biaxial dislocation testing platform. A three-dimensional finite element model was developed and validated. Comparative analysis of three anti-dislocation structural systems was performed. Experimental results indicated that tunnel structures underwent significant bending moments and shear forces under strike-slip fault dislocations. The airbag-off-wall system effectively safeguarded the main tunnel structure during fault events. During minor dislocations, the airbag reinforcement considerably enhanced the compressive stiffness of the system. Under large dislocations, the pressure-regulated airbags mitigated direct damage transfer to primary structural elements through active pressure relief. The inner lining maintained structural integrity even under a model dislocation of 50 mm (equivalent to 2.5 m at prototype scale). However, transient pressure spikes caused by delayed relief led to localized stress concentrations. A rapid airbag pressure release mechanism can alleviate the risk of inner lining cracking.

Damage to tunnel structures under seismic action severely affects engineering safety and post-earthquake rescue, making it crucial to enhance the seismic capacity of tunnels. Current seismic approaches for tunnel engineering mainly include seismic isolation (shock absorption layer technology), damping, and anti-seismic, among which shock absorption layer technology has attracted considerable attention due to its economic efficiency and effectiveness. However, existing research has primarily focused on single shock absorption layer materials, lacking systematic classification frameworks and multi-dimensional comparative analyses, making it difficult to provide comprehensive guidance for material selection and engineering applications. This paper systematically reviews the research status of tunnel shock absorption layers. First, it elucidates three core mechanisms through which shock absorption layers function: wave-impedance mismatch and energy reflection, material damping and energy dissipation, and system stiffness reduction with natural period elongation. This study proposes categorizing the existing materials for tunnel shock absorption layers into five main types: foam concrete, other types of concrete, polymer materials, asphalt materials, and porous metallic materials. A detailed introduction is provided for each material category, covering their physical properties, shock absorption performance, advantages and disadvantages, as well as relevant optimization studies conducted to address material limitations. By comprehensively comparing the mechanical properties, shock absorption performance, durability, constructability, recyclability, and economy of these five types of materials, revealing their unique advantages and applicable limitations in tunnel shock absorption. Finally, the limitations of existing research are summarized, development directions for tunnel shock absorption layer materials are proposed, and the future research trend of tunnel damping layer technology is envisioned. This paper provides a reference for the research, selection, and standard formulation of tunnel shock absorption layer materials.

Dynamic response tests using a shaking table were conducted to directly measure the time-history relationship of ductile displacements in cast-in-place horseshoe-shaped mountain tunnels. These tests provided displacement and maximum deformation rate (MDR) control indices for the tunnels. Shaking table tests on such tunnels have typically focused on seismic mechanisms, primarily through measurements of acceleration, strain, strength, and internal forces. However, research on ductile displacements and deformation rate control indices remains limited. In this study, a novel experimental methodology was developed and utilized to directly quantify the time-history relationship of ductile displacements in mountain tunnels. A series of shaking table tests were conducted to evaluate the seismic performance, influence extent, and impact range of the tunnels. The seismic response characteristics and damage assessment under various conditions were systematically investigated. The primary conclusions are summarized as follows: (1) The practicality and effectiveness of the method for directly measuring the time-history relationship of ductile displacements were validated through testing and analysis. (2) Recommended MDR thresholds for ductility indicators in mountain tunnels are proposed, with values of 8.27 %o, 6.09 %o, and 4.85 %o for shallow-buried, medium-buried, and deep-buried tunnels, respectively. (3) Burial depth is identified as a critical factor influencing the seismic performance of mountain tunnels, with both displacement and MDR showing a decreasing trend as burial depth increases. (4) Based on the seismic response characteristics and damage patterns of cast-in-place horseshoe-shaped mountain tunnels, four distinct damage patterns were identified: elastic, elastoplastic, plastic-critical, and critical-collapse. These findings provide a foundation for predicting damage and failure, as well as for developing probabilistic seismic demand models for cast-in-place horseshoe-shaped tunnels under seismic loading, thus offering valuable references for the establishment of relevant industry standards and guidelines.

A shaking table model test of the tunnel was carried out to compare the damping effects of polyurethane foam aluminum(AF/PU) and sponge rubber. The test shows that the damping effect of polyurethane foam aluminum is better, and the dynamic earth pressure and strain values of each measuring point of the tunnel lining are relatively smaller. The ANSYS software was used for the ground motion simulation. The first principal stress and first principal strain of the lining were compared and analysed between the two types of damping layers. It was found that the damping effect of AF/PU was better, which is consistent with the test results. The damping effects of AF/PU with thicknesses of 10, 20, and 30 cm were 22.3%, 29.03%, and 31.41%, respectively. The damping effect increases with an increase in thickness, but the growth rate slows.

To analyze the damage distribution characteristics and ultimate bearing capacity of tunnel linings under seismic action, damage variables were introduced into the Mohr-Coulomb constitutive model. Thus, an incremental elastic–plastic damage constitutive model for concretewas constructed. Uniaxial tensile and compressive tests were performed to verify model reliability, and the damage thresholds for different strength classes of concrete under the test conditions were numerically obtained when destruction occurred. These damage thresholds were considered as the criteria for material failure to solve the ultimate bearing capacity and failure form of the tunnel structure. Calculation results demonstrate that as the peak ground acceleration increases, the shallowly buried tunnel structure presents the three following stages: elastic bearing, local instability, and overall instability. If the compression or tensile damage values of an element exceed the threshold value, the element is regarded as destroyed. The failure of any element of a structure can be used as a criterion for local instability. If the volume of the destroyed elements exceeds 10

The discharge of groundwater and the load on the lining structure are both significantly impacted by the obstruction of the tunnel drainage system. In this study, the fluid–structure interaction model was established based on the finite difference software FLAC3D. Then, this research explored the effects of symmetric and asymmetric blockage in the circular drainpipe, the transverse drainpipe and at the pipe joint in the tunnel on the pore water pressure, displacement and stress of surrounding rock. Our research revealed the following points: (1) When a symmetrical or asymmetrical blockage occurred in a circular drainpipe, only the blocked part of the drainpipe would be affected, but the pore water pressure at the back side of the tunnel crown and side wall lining between two adjacent circular drainpipes would increase by 200%, stress increase would increase by 22% and displacement would increase by 41%. (2) When a symmetrical or asymmetrical blockage occurred in a transverse drainpipe, the pore water pressure at the back side of the tunnel crown and side wall lining between two adjacent circular drainpipes increased by a maximum of 146%, the stress on the tunnel crown lining increased by a maximum of 4% and the tunnel crown lining was displaced by 8% to a maximum extent. (3) Both symmetrical and asymmetrical blockage of the tunnel drain joint led to the failures of the circular drainpipe and the transverse drainpipe connected with the tunnel drain joint. This increased the pore water pressure on the back side of the lining between the two adjacent drain sections and had an impact on the pore water pressure, stress and displacement of the surrounding rock nearby.

To explore the mechanical properties of cracked lining subjected to seismic loads based on wave theory and the extended finite element method, the dynamic viscoelastic boundary of a seismic wave and equivalent nodal force load were generated by MATLAB programming software to establish a simulation model of cracked lining structure. The internal force state change law of the lining structure was studied by varying the crack depth, crack length, secondary lining thickness, and other parameter values (including the layout between multiple cracks). Also, the safety factor of the lining crack section was obtained, and the functional relationship between the safety factor and parameter variables was established. Results show that the crack depth and secondary lining thickness were the main factors affecting the internal force of the crack section. Based on the least square method, the calculation formula and 95 % confidence interval between the minimum safety factor (Kmin) and each parameter of the crack section were obtained. Meanwhile, the Kmin prediction model was obtained via multiple nonlinear regression. When the crack depth value was 30 % of the lining thickness value, Kmin reduced 2.5 times. At 57 % crack depth of the lining thickness, the Kmin was less than the specification value, indicating that the lining structure’s safety reserve was low. Compared with the arrangement of the vertical distribution of the two cracks, the stress concentration generated when the two cracks were arranged in parallel would more likely affect the structure adversely. The findings can provide a reference for the safety study of cracked tunnels.

To study the dynamic response law of large-section cracked lining structures under seismic waves, comparative tests of large-scale shaker tunnel models of non-destructive lining structure (model 1), a crack in the vault of the lining structure (model 2), and two parallel cracks in the vault of the lining structure (model 3) were carried out by applying 0.1-1.0 g progressively increasing the peak acceleration of the input waves. This paper visually showed the distribution of cracks in three groups of the lining structures. In addition, the acceleration response of the lining and surrounding rock, dynamic soil pressure, the dynamic strain on the inner and outer surfaces of the lining, and dynamic internal force variation were obtained, and the seismic performance of three groups of lining structures was discussed. The results showed that the seismic weak positions of model 1 were the arch shoulder and the arch foot, the seismic weak positions of model 2 were the arch shoulder, the arch foot, the initial damage area, and the inverted arch, and the seismic weak positions of model 3 were the positions of the arch foot, the cracks of the vault, the inverted arch, and the arch wall. The soil pressure values at the vault of three groups of models were model 2 > model 1 > model 3 in turn. The surrounding rock amplified the input seismic waves. With the gradual increase of the peak acceleration, the seismic energy was gradually consumed due to plastic damage to the lining structure or the loosening and destruction of the overlying soil, resulting in the acceleration amplification coefficient value of the surrounding rock in the upper part of the lining structure showing a changing trend of first increasing and then decreasing. When the peak acceleration was 0.2 g, the crack propagation phenomenon occurs in the initial crack position of model 2 and model 3. When the peak acceleration was 0.4 g, the cracking phenomenon occurs at the right arch foot of model 1. The above phenomenon confirmed the conclusion that cracks can weaken the seismic performance of the structure. When the peak acceleration was 0.8 g, the peak values of the amplification coefficient of the lining at the inverted arch and near the filled soil surface were about 1.2 and 1.6 respectively. The research results can provide a reference for the seismic performance evaluation of cracked tunnels.

Skiving is an efficient gear cutting technology with relatively high machining accuracy, especially for internal gears. Nevertheless, the machining accuracy can hardly be satisfied if the skived gear is modified, so we try to extend the definition and hypotheses domain of the previous works. In this paper, fundamental research is conducted to further improve the skiving accuracy. Firstly, a new type of skiving tool with double rake faces is proposed for flexibly meeting different modification requirements of the two flanks of the work gear teeth. Secondly, the mathematical model of curve-surface conjugated cutting edges of the skiving tool for enveloping the tooth flanks of the working gear with profile modification is established. Then, the algorithm of the skiving tool path with alterable shaft angle in the cutting process is proposed for eliminating the twist of gear tooth flanks with lead modification. Finally, machining simulations are carried out to verify the feasibility of the proposed improved skiving methods.

Geological faults impair tunnel stability during earthquakes. This study establishes a tunnel dynamic stability evaluation index based on load/unload response ratio (LURR) theory. It considers a seismic wave as a load/unload parameter and tunnel structure strain response as a response parameter. The rationale behind this evaluation index and the factors affecting tunnel stability across fault zones under seismic conditions are investigated. Compared to the traditional dynamic instability criterion, the LURR accurately measures the degree of structural deviation from the steady state and better determines the potential destabilization region of the structure. As the peak value of the input seismic wave increases, the LURRs of the more unstable parts increase, while the LURRs of the stable parts remain unchanged. According to LURR theory, the size of the range affected by the fault on the tunnel during an earthquake depends mainly on inherent fault properties (i.e., the dip angle, strike, and thickness), independent of the earthquake intensity. Because the LURR can theoretically be infinite, its dynamic instability threshold cannot be determined accurately.

Large deformation of surrounding rock makes the internal space of a tunnel cannot meet the requirements of normal use after support, even leads to the instability of surrounding rock and destruction of the tunnel structure. In order to optimize the parameters of the primary support to control the deformation of surrounding rock, field tests and numerical simulations are carried out. Based on the engineering geological conditions and the deformation monitoring data of surrounding rock, four important creep parameters of the improved Burgers model are inversed by numerical simulation, considering the creep of surrounding rock in tunnel construction. The results show that it is feasible to use tunnel crown settlement as a control indicator to determine the thickness of shotcrete. Short rock bolts are preferentially used in the tunnel arches, and a combination of long and short rock bolts should be used on the sidewall to control the large deformation of surrounding rock. When the excavation method of upper-lower bench is used in the single-track railway with a relatively large high-span ratio, the horizontal convergence monitoring points of the upper bench are recommended to be set 0.8-0.9 times the height of the upper bench from the tunnel arch crown, and those of the lower bench are recommended to be set 0.6-0.7 times the total height of the upper-lower bench from the tunnel arch crown.

To obtain the method for static instability criterion of tunnels, the loading/unloading response ratio (LURR) theory is introduced into the analysis method. The nonlinear characteristics and the LURR variation laws of unlined circular tunnels under symmetrical loads are analyzed through the analytical method, and the results have proved their relevance. The research approach of LURR method is put forward based on the different loading characteristics of construction and operation tunnels. The critical conditions and the LURR variation laws of tunnels with and without linings are analyzed respectively through the finite element method. The results show that the nonlinear characteristics based on the LURR theory of tunnel deformation calculated by the analytical solution and the finite element solution are similar. The LURR variation laws of tunnel deformation are different in each loading and stability stages of tunnel system, the LURR variation rate in the weak area of the tunnel will be abnormal before its instability, and the abnormal variation trend is the precursor criterion of the instability of the tunnel system. Based on the determination of the ultimate bearing state of the tunnel system by the LURR method, the safety factor of the tunnel system is obtained by using the loading ratio. The static instability method based on the LURR theory of tunnels is proposed.

The tunnel shaking table model test has many influencing factors, and the test parameters are difficult to meet the strict similarity ratio. There are often large errors in predicting prototypes directly using the similarity ratio derived from the classical similarity theory. In order to improve the prediction accuracy of the tunnel shaking table model test, this article proposes a modified method of the traditional similarity theory. Based on the traditional dimensional analysis method, this method uses a non-direct similarity technique to rebuild the dimensional matrix for the main test parameters, derive a new similarity criterion, and then obtain a new similarity ratio. Different from the traditional similarity ratio which is a certain value, the new similarity ratio varies with dynamic parameters, which is more consistent with the actual situation. The tunnel shaking table model test and numerical simulation are carried out to verify the method. Experiments show that the modified method is superior to the traditional similarity theory in numerical prediction accuracy.

目的 利用CRISPR/Cas9系统构建腺苷酸激活蛋白激酶 α1(adenosine 5′-monophosphate-activated protein kinaseα1,AMPKα1)基因敲除的小鼠胚胎成纤维细胞3T3-L1细胞系,为研究AMPKα1在脂肪细胞中的生物学功能提供细胞模型.方法 在NCBI上查找AMPKα1基因序列,利用张锋实验室网站设计sg RNA.利用lenti CRISPR质粒构建AMPKα1敲除质粒,构建好的质粒与辅助质粒共同转染293T细胞获得慢病毒.用病毒液感染目的细胞3T3-L1,嘌呤霉素筛选感染成功的细胞.将3T3-L1细胞诱导成成熟的脂肪细胞,与RAW264.7细胞共培养48h,检测RAW264.7细胞中核转录因子 κB(nuclear factor kappa-B,NF-κB)表达情况.结果 蛋白质印迹(Western blot,WB)法与Q-PCR法检测结果表明获得稳定敲除AMPKα1的3T3-L1细胞(P<0.01);与RAW264.7细胞共培养WB法检测RAW264.7细胞中NF-κB.结果 表明,AMPKα1敲除的成熟脂肪细胞分泌因子增加巨噬细胞RAW264.7细胞中的NF-κB蛋白表达.结论 本研究利用成簇的规律间隔的短回文重复序列/Cas9核酸酶(clustered regularly interspaced short palindromic repeats/Cas9,CRISPR/Cas9)系统成功构建了AMPKα1敲除的细胞系,为后续深入研究AMPKα1基因在3T3-L1细胞系中的作用及其机制奠定了一定的基础.

城市地下交通联系隧道受其平面曲线半径和纵坡的影响,沿程阻力系数变化规律不同于普通公路直线隧道和一般的曲线隧道.以解放碑地下环道三期工程嘉滨路连接隧道通风工程为依托,采用CFD软件,进行不同平面曲线半径和不同纵坡率的流场数值模拟,从沿程阻力系数值、断面风速等方面进行了分析,数值模拟结果表明纵坡对隧道的阻力损失没有明显的影响;而半径影响较大,尤其是当半径小于200 m后,沿程阻力系数增加尤其明显,并对半径在30～200 m范围内的城市超小半径隧道沿程阻力系数计算公式进行了优化.

It is necessary to set up slagging well to facilitate slagging and improve construction efficiency during the construction of tunnel shaft inverse well method. Due to the geological condition of the shaft and human factors, the slag chute is easily blocked and the construction period is affected. The conventional dredging method has some problems such as low efficiency, complicated process and long time limit. In this paper, based on Yunnan province Taihe Sumie to Lincang highway tunnel shaft engineering, put forward a way to use two strands in a certain distance between wire rope clamp, two of the same height of the steel wire rope clip through the switch assembly structure of the hinge connection, can be efficient and convenient to dredge the well construction shaft sneak slag well jam problem, as a reference for other similar projects.

The model of efficiency-cost ratio for after-shock masonry strengthening is established, considering the number of stories, material strength, seismic damage, the promotion of seismic capacity, and the engineering cost. Based on the model, the optimal selection method for masonry strengthening is proposed, combining the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), including the construction time, technology, durability, and the impact on architectural function. Comparative cases are performed to study the influence on the optimal selection results by the number of stories, by the material strength, and by the seismic damage level. It is concluded that: the proposed method can reflect the influence on the strengthening decision making by the basic structural conditions, and effectively provide a scientific and reliable scheme for masonry buildings, combing the subjective and objective factors during the preliminary design stage.