The underground solution mining of salt cavern energy storage is hard to observe or control. Therefore, a solution mining model is needed for the design, prediction and control of the cavern development, to make sure the final cavern shape meets the long-term stability requirements. The progress was concluded about the solution mining mechanism and modeling method, including the salt dissolution rate, brine convection model, collapse of the insoluble interlayers, and sedimentation of the insoluble substances. The main problems and development tendency was pointed out for the salt cavern modeling and design.

When the depth of a cavern is shallow or the surrounding rock is hard, the stability problem of surrounding rock mass of cavern is often manifested as local block failure. Block theory is essentially a geometric topological method, and it is an ideal tool to analyze the stability of block formed by mutual intersection of fractures. The application and development of block theory in stability analysis of surrounding rock of caverns were discussed systematically. The main analysis techniques included: selection of the axis of cavern based on the movability and morphology of block, morphology analysis of maximum block and definition of support-required block, determination of size of non-localized block based on the extent of discontinuities, morphology analysis of localized blocks, analysis of block stability, and analysis of block support as well. The problems associated with these analysis techniques in application were also discussed.

For stability analysis of ultra-deep shaft surrounding rock, based on the elastic-plastic constitutive model and Mohr-Column failure criterion, the disturbance stress reaction process of the shaft excavation was simulated by reducing the radial support stress at the excavation boundary of shaft. The reaction mechanism of the disturbance stress was described based on the evolution of disturbance stress and failure of shaft surrounding rock, and then the results of current study on the disturbance stress mechanism of shaft longitudinal section were summarized. As the shaft goes deeper, the instability type of the new main shaft surrounding rock was divided into three categories: the structure controlling instability type, the stress controlling instability type and the transformation type from structural controlling instability to stress controlling instability. At the same time, based on the reaction mechanism of disturbance stress caused by shaft excavation and utilizing various rock failure criteria, the longitudinal instability zone was divided for the new main shaft. The calculating results showed that the structural controlling instability of shaft surrounding rock was between 0 m and 387 m, the transformation zone from structural controlling instability to stress controlling instability was between 387 m and 654.7 m, and the stress controlling instability type appeared between 654.7 m to 1 527 m.

Based on one typical excavation project of shield working well in Hangzhou where the soft soil was over the hard soil, this paper monitored and analyzed the horizontal displacement of the wall, ground settlement, surrounding building settlement, and strut force during its excavation. The results showed that: with the excavation of the foundation pit in upper soft and lower hard soil layer, the distribution of the horizontal displacement of the wall along the depth of the foundation pit had two forms: single peak and double peak, the maximum horizontal displacement of the wall was between 0.56‰-0.59‰ H(H is the excavation depth of the working well); The maximum horizontal displacement of the wall was about 5 m above the soil-rock interface. The ground settlement curves were mainly in the form of “inverted triangle-shaped” and “spoon-shaped”, the sensitive area of the settlement was mainly distributed in the range of about 0.36-0.73 H from the edge of the foundation pit and the maximum settlement was about 1.36‰-2.61‰ H; The excavation phase of the soil below each support was the main growth period of the corresponding strut force. Thereinto, the strut force value of the concrete support was affected by the curing time, and it must be guaranteed to reach 28-day strength before excavation.

Soft rock under high stress is prone to occur large deformation, and jamming disasters often encounter when TBM passes through such stratum. Currently, there is no classification standard that can directly guide TBM construction adaptability for large-deformed surrounding rocks. Analyzing the advancing state of TBM, the deformation of surrounding rock and the pressure on the shield were regarded as the main indexes. The contact state of the surrounding rock and TBM was distinguished according to the relationship between the rock deformation and overcut size; and the state of shield stress was distinguished according to the relationship between the shield friction and TBM ultimate thrust. Moreover, considering the accessibility and universality of surrounding rock classification, the classification standard of TBM construction adaptability for large deformation surrounding rock was established according to the potential jam status of TBM. The classification standard was applied to a specific project to verify its reasonability. The results showed that the TBM construction adaptability classification for large-deformed surrounding rock required taking rock deformation and shield stress into consideration comprehensively. The proposed standard could guide projects directly and effectively to avoid jamming disasters.

Excavation unloading of tunnels in soft weak surrounding rock forms a wedge-shaped plastic zone. Based on the shear-slip line theory proposed by RABCEWICZ L V et al, the supporting resistance provided by the anchor bar, shotcrete layer, steel mesh, and steel arch at the shear height was calculated and applied to the excavation outline in reverse. The numerical model of the double-arch tunnel of a section of Guiyang rail transit line 2^# was built, and the construction scheme of middle guide hole-stairs method was used to simulate the excavation and support process, and the deformation and damage effect could be obtained, which were compared with the monitored data of the typical cross-section such as settlement, side wall convergence and roof arch settlement. The research results showed that the shotcrete-anchor support measures reduced the deformation of the surrounding rock, effectively relieved the stress concentration phenomenon after excavation, and the multi-arch effect of mid-partition wall was very obvious. The supporting structure and surrounding rock together layed an important role of common bearing circle, which may keep the whole tunnel stable.

Using the numerical simulation model, the effects of the surrounding rock deformation capacity, lining concrete label, backfill grouting pressure, and grouting stone deformation capacity on the hydraulic head of the hydraulic pressure tunnel lining and the joint bearing ratio of the surrounding rock and lining were analyzed. The result showed that: the elastic modulus of the surrounding rock had a significant effect on the joint bearing ratio of the surrounding rock and the lining. When the higher the elastic modulus of the rock mass, the greater the load shared. The effect of the lining concrete label and the grouting stones was small, and the backfill grouting pressure had no effect basically. The modulus of surrounding rock and grouting stones, grouting pressure increased, and the internal water head required for lining cracking increased. The influence of elastic modulus of surrounding rock and backfill grouting on cracking head was more obvious, but due to the concrete rank increase, the lining load sharing ratio increased, and the lining cracking head gradually decreased. The research results could provide support for the design of hydraulic pressure tunnel lining and the reasonable selection of grouting parameters.

The stratum of a certain foundation pit in Jingdezhen is mainly pebble and limestone. In order to meet the requirements of construction operation space and construction schedule, the original design plan adopts a pile-anchored enclosure structure. During the excavation of the foundation pit, the enclosure structure was deformed greatly, threatening the safety of the project, and relevant measures need to be taken for protection. The possible causes of the larger deformation of the retaining structure, and the results showed that the larger deformation of the retaining structure was caused by the failure of the prestressed anchor cable. In view of the current situation, a solution of constructing a local main structure with temporary internal bracing was proposed, and the finite element numerical method was used to simulate the support effect of the original retaining pile and the improved plan. The research showed that the improved scheme could effectively control the deformation and bending moment of the retaining pile, and met the requirements of the corresponding monitoring and measuring early warning value, which could provide reference for related projects.

Based on the dynamic design of the large deformation of weak surrounding rock in Muzhailing Tunnel, the article introduced the special geological environment of the tunnel, analyzed the causes of the primary support intruding into tunnel structure gauge and the secondary lining cracking during construction, and studied the special measures to solve the problem of the large deformation in weak surrounding rock with extreme crustal stress, such as the multiple support system, enlargement of the advance heading for stress release, the reinforcement of long system anchor bolt(anchor cable), the reinforcement of invert steel truss and the setting of cushion structure. The engineering practice suggested, the technical countermeasures adopted were safe, reliable and effective, and the problems to be solved in construction were discussed, which could be used for reference in similar projects.

When the subway goes under the station building of the railway station, it is easy to cause surface settlement, which in turn leads to instability of confining pressure, difficulty in construction, and increased costs. For engineering construction, it is still necessary to study the construction mechanics behavior in the underpass section. Based on Guiyang Metro Line 1 Railway Shachong Road Station Section(Huo-sha Section), combined with the numerical simulation software FLAC^3D to establish an analysis model of the tunnel passing through the train station, and study the subgrade settlement changes, dark the internal force and safety factor of the lining structure in the excavation section. The results showed: with the gradual excavation of subway tunnels, the subgrade settlement of the railway station yard gradually increased, but it did not exceed the existing railway deformation control standards in the underpass section; after the construction of the secondary lining structure, the longitudinal distribution of the existing railway settlement was approximately a normal distribution curve, consisted with the change law of the surface settlement trough proposed by Peck, and the settlement range was from -50 to 50 m; the stress of the masonry structure was mainly concentrated on the wall waist and vault of the interval lining structure, the deformation types of the secondary lining structure were large eccentricity and small eccentricity, the axial force value gradually increased from the vault to the foot of the wall to both sides, and the two sides were basically symmetrical, the maximum axial force appeared at the foot of the wall; after the deformation of the secondary lining structure was stable, the maximum settlement value of the roadbed settlement at the intersection was 2.87 mm, which met the deformation control standard of the existing railway under the station yard.

The medium plates of the large-span underground excavated column-free station had been categorized into arched support structure, plate diagonal structure and variable cross-section structure with thick plate. Three-dimensional modeling had been carried out on the medium plates of three types, using Midas GTX software. The load structure method had been used to numerically analyze the inner force of the medium plates, the mid-span deflection and the force on the side beam of hole. The calculation results showed that the internal force distribution and deformation of the arched support structure and the plate diagonal structure were basically the same and smaller than those of the variable cross-section structure with thick plate. Under the same load conditions, the internal force distribution of the arched support structure was the best; variable cross-section structure with thick plate occupied the smallest layer space of the station, but had the largest internal force and deformation, thus with high demand on construction. The plate diagonal structure was simple with reasonable internal force distribution, and was convenient for on-site construction. The arched support structure and the plate diagonal structure have been successfully applied in Qingdao Metro Line 1 and Line 6 projects, providing a useful reference for similar projects in the future.