This study aimed to enhance shield muck by incorporating foam agent and active magnesium oxide. The fluidity, bleeding rate and compressive strength of the improved soil under different foam agent and active magnesium oxide content were obtained by fluidity, bleeding rate and compressive strength test. It was showed that the improved flowable backfill soil exhibited excellent fluidity and solidified strength. By adjusting the content of foam agent and active magnesium oxide, the flowable backfill soil with fluidity ranging from 180 mm to 320 mm, bleeding rate below 5%, and 28-day compressive strength between 0.6 MPa and 1.2 MPa could be obtained.

In order to explore the main influencing factors and control methods of secondary disasters of water and mud inrush in underground engineering, the prevention and control technology of secondary disasters of water and mud inrush was proposed by summarizing relevant cases since 2010 and the disaster-inducing environment and factors were summarized. Taking the secondary water and mud inrush of Shizishan Tunnel crossing F_Ⅲ-71 fault in central Yunnan as an example, the causes of disasters in this geological section were explored, and the evolution process of secondary disasters was divided into three stages: gestation stage, latent stage and induction stage. The methods of improving the state of the external environment, blocking the evolution path of the disaster and increasing the bearing capacity of the anti-outburst layer were put forward to prevent the recurrence of water outburst and mud outburst, which provided experience guidance for the treatment of the secondary disaster of water outburst and mud outburst.

To investigate the effects of measures such as grouting and lining drainage on high external water pressure acting on lining in deep-buried tunnels, the Songlin Tunnel of Yunnan Central Water Diversion Project was selected as the study object. Numerical simulation calculation was conducted to investigate the variation of the surrounding rock seepage field and lining structure external water pressure under different grouting ring parameters and lining drainage conditions in the deep-buried water diversion tunnel. Based on the results, proposals for optimizing the design of surrounding rock consolidation grouting and lining drainage were presented. The research findings revealed that setting grouting rings and lining drainage holes in the surrounding rock could effectively reduce the external water pressure on the lining structure. The thicker the grouting ring was, the smaller the permeability coefficient was, and the better the water plugging effect was. The more drainage holes in the lining, the smaller the external water pressure on the lining structure, but the safety of the lining should be considered when setting the drainage holes. It was recommended that the grouting ring thickness should be set at 6-8 meters, and the grouting ring conductivity coefficient should be set at 1/60 to 1/40 of the permeability coefficient of the surrounding rock. The number of drainage holes should be set at 2-3, which was a more reasonable design range.

Aiming at the problem of demolition of existing concrete buildings in underground space construction, the effects of different water jet parameters and cutting process parameters on the performance of high-pressure water jet damaged concrete were systematically investigated through indoor experiments and numerical simulations, and the stress distribution and crack extension characteristics of concrete under the impact of water jet were analyzed. The test results showed that the depth of high-pressure water jet cutting concrete increased linearly with the increase of pump pressure, increased first and then decreased with the increase of target distance, decreased with the increase of the number of cutting growth rate, with the decrease of traverse speed growth rate gradually became larger. The effective stress near the center point of the high-pressure water jet impact exceeded the strength of the concrete, leading to the failure of the concrete. Cracks propagate along the peak point of the effective stress and continuously penetrated to form flaky spalling. In addition, for water jet cutting of strongly restrained concrete, the main damage was dominated by water jet cutting joints and surface concrete flake spalling, while for weakly restrained concrete, the damage was dominated by segmental excision. When there was a free surface inside the concrete, it was more likely to form through cracks and produce a large-volume breakage.

In order to study the deformation law of soft rock tunnels within high geo-stress, the paper quantitatively analyzed the relationships between the deformation value with the compressive strength of rock mass, the integrity of surrounding rock, the geo-stress & depth of tunnel, the coefficient of lateral stress, the ground water, the value of basic quality［BQ］ and the stiffness of support of soft rock tunnel within high geo-stress based on the statistics of monitoring dada from 68 monitoring sections in 41 tunnels. The results indicated that the large deformation of surrounding rock in soft rock tunnel within high geo-stress was the outcome of the comprehensive action of geological conditions of surrounding rock, the design and construction parameters and other factors. Among them, the in-situ geo-stress, surrounding rock characteristics and supporting countermeasures had the significant influence. The results from the case statistics could preliminarily reveal the development level of the control technology of large deformation of soft rock traffic tunnel within high geo-stress in China. The deformation of soft rock tunnel within high geo-stress had noticeable time-space effect with the variation patterns from the rapid growth stage to the continuing growth stage and then the stabilizing stage at last with time. The deformation coordination coefficient was mostly affected by the excavation with large fluctuations in the early stage, but tended to be stable very soon after the inverted arch was constructed which also verified and emphasized the key role of the ring closure to the deformation control from another perspective. With the increase of large deformation grade, the proportion of the deformation after construction of inverted arch decreased.

In order to analyze the influence of sulfuric acid corrosion on the mechanical properties of the deep water storage and sewage tunnel lining structure(short for “deep tunnel”), this research carried out sulfuric acid corrosion tests with initial pH=1 on the standard concrete specimens with a steel fiber volume ratio of 0% and 1%, and considered two corrosion conditions of single-face and all-face immersion. The surface pH value, mass change rate, uniaxial compressive strength and reaction products of concrete specimens under different corrosion time were systematically analyzed. The results showed that the concrete's strength changed nonlinearly with corrosion time. Because the addition of steel fiber resists the diffusion of sulfuric acid, the reaction process in the early stage of corrosion was slowed down and the reaction products were reduced. Therefore, the strength and quality of steel fiber concrete under acid corrosion immersion did not change as rapidly as that of plain concrete under the same condition. The mass increase rate of concrete specimens under all-face immersion was greater than that of specimens soaked on one side under the same conditions. Combined with XRD analysis, it could be seen that gypsum was formed after reaction. The contact area between all-face corrosion and sulfuric acid was larger, so the reaction products were generated faster, and the corresponding strength and mass increase were also faster.

Based on the spillway tunnel project of Jinchuan Hydropower Station, this research introduced the microseismic monitoring technology to monitor the deformation and failure of surrounding rock in real time, and studied the spatio-temporal evolution characteristics of microseismic events in surrounding rock of spillway tunnel. The failure mechanism of surrounding rock in spillway tunnel of Jinchuan Hydropower Station was analyzed by means of energy ratio of transverse and longitudinal waves E_S/E_P. The fractal rock mechanics theory was introduced into the field of microseismic, and the spatiotemporal evolution of the fractal dimension of energy released by microseismic was analyzed. The relationship between the fractal dimension and the deformation of surrounding rock in time and space was revealed through the comparative analysis of the evolution law of the fractal dimension and conventional monitoring data. The fractal dimension of the microseismic energy of rock mass before the deformation occured would appear dimension reduction in time and space, which could be used as a warning signal.

In order to study the long-term stress characteristics of super-long cast-in piles, taking the construction Project of the second building in the North District of a Talent apartment in Shenzhen as the research background, the long-term monitoring of piles for nearly two years was monitored based on distributed optical fiber sensing technology. The strain transfer coefficient of the armored distributed optical fiber sensor was studied by laboratory tests; Combined with the hyperbolic model of the pile-soil interface, the long-term load variation law of super-long and large-diameter cast-in-place piles was revealed. The results showed that the strain transfer coefficient of the armored fiber was about 0.668 and did not depend on the load and time. The superlong and large-diameter cast-in-place pile mainly bore the upper load by the middle and upper part of the pile body. The axial force and lateral friction of pile body increased positively with the number of completed floors. When the construction was completed, the transfer coefficient of pile side friction resistance was about 52.64%, and the surface pile was in a safe state in terms of bearing capacity.

This research summarized the basic concepts of compressed air energy storage(CAES)underground caverns from an engineering perspective, analyzed the basic structure of caverns and the main load characteristics of caverns during operation. On this basis, the basic design concept of flexible sealing structure was put forward, and the reliability design method was suggested to be adopted in the construction of underground caverns, which also provided the guidance and design principles, operation, and maintenance of CAES underground caverns.