Significant movement of in-situ retaining walls is usually assumed to begin with bulk excavation. However, an increasing number of case studies show that lowering the pore water pressures inside a diaphragm wall-type basement enclosure prior to bulk excavation can cause wall movements in the order of some centimeters. This paper describes the results of a laboratory-scale experiment carried out to explore mechanisms of in situ retaining wall movement associated with dewatering inside the enclosure prior to bulk excavation. Dewatering reduces the pore water pressures inside the enclosure more than outside, resulting in the wall moving as an unpropped cantilever supported only by the soil. Lateral effective stresses in the shallow soil behind the wall are reduced, while lateral effective stresses in front of the wall increase. Although the associated lateral movement was small in the laboratory experiment, the movement could be proportionately larger in the field with a less stiff soil and a potentially greater dewatered depth. The implementation of a staged dewatering system, coupled with the potential for phased excavation and propping strategies, can effectively mitigate dewatering-induced wall and soil movements. This approach allows for enhanced stiffness of the wall support system, which can be dynamically adjusted based on real-time displacement monitoring data when necessary.

Shield tunneling inevitably disturbs the surrounding soil, primarily resulting in changes in stress state, stress path, and strain. Modifications to certain parameters, such as shield thrust, shield friction, and soil loss, are made based on the elastic mechanics Mindlin solution and the mirror method, and a calculation expression for additional soil stresses induced by tunneling was derived. Additional soil stresses are calculated using the parameters of the Hangzhou Metro Kanji section. 3D principal stress paths and deviations of the principal stress axes near the tunnel crown, waist, and invert during shield tunneling were obtained by applying a transition matrix orthogonal transformation. These results are compared with experimental data to validate the theoretical solution's accuracy. The stress distribution along the tunneling direction and the 3D principal stress paths and deviations of the principal stress axes in the surrounding soil are determined. The results are as follows: The additional soil stresses along the tunneling direction follow a normal distribution and an S-shape. Under the combined influence of three construction mechanics factors, the shear stress component is approximately 1/3 to 1/2 of the normal stress and should not be neglected. During shield tunneling, the deviation angle of the principal stress axis at the tunnel crown changes from 90 degrees to 180 degrees, with little change in the magnitude of the principal stress. At the invert, the magnitude of the principal stress rapidly increases from 0.25 kPa to 8 kPa, with minimal deviation in the principal stress axis. At the shoulder, the principal stress variation and axis deviation are small. At the foot of the arch, the deviation angle of the major and minor principal stress axes is larger, while the magnitude of the principal stress slightly changes. At the waist, the deviation angle of the major principal stress is larger, and the magnitude of the minor principal stress significantly changes. A strategy for addressing changes in soil stress paths during shield tunnel construction is also proposed.

The Traffic Speed Deflectometer (TSD) is a mobile vehicle that measures deflection slopes. Deflection slopes have been utilised in previous studies to backcalculate pavement layers' moduli. However, the nonlinear stress-dependency and cross-anisotropy of unbound granular materials and fine-grained soils were overlooked in those studies. Utilising the Finite Element Method (FEM) based on static analysis in this study to evaluate a three-layered flexible pavement system with specific material properties and layer thicknesses revealed that neglecting the nonlinear stress-dependency of base and subgrade layers underestimated the permanent deformation life of the backcalculated pavement by more than 45%. Neglecting the cross-anisotropy of the base layer with the design anisotropy ratio of 0.5 increased the backcalculated Asphalt Concrete (AC) modulus by more than 21%, increased the estimated permanent deformation life of the pavement by more than 160%, and decreased the backcalculated base modulus by around 28%. Neglecting the cross-anisotropy of the subgrade with the design anisotropy ratio of 0.5 almost increased the estimated permanent deformation life of the pavement by 15%. The results underscore the necessity to consider the nonlinear stress-dependency and cross-anisotropy of unbound granular materials and fine-grained soils in backcalculating pavement layers' moduli from TSD deflection slopes.

Reliable predictions of time-dependent diaphragm wall deflections in deep excavations in soft soils are crucial for managing potential damage to the surrounding environment. Bayesian updating offers a rational method for refining these predictions by using monitoring data. The inconsistency in monitoring data necessitates an examination of the impact of using different datasets on Bayesian updating. This paper presents a Bayesian updating of time-dependent deflections of diaphragm walls in deep excavations in soft soils using different datasets. The soft soil creep model is utilized to simulate the time-dependent behavior of soil. Bi-directional longshort memory neural networks are employed as surrogate models. Different updating strategies with varying numbers of data in the datasets are adopted for Bayesian updating and illustrated with the Taipei National Enterprise Center project. The results show that incorporating more monitoring data in the datasets for Bayesian updating does not guarantee better predictions unless the consistency of the monitoring data used is ensured. Additionally, the Bayesian updating process more accurately predicts short-term deflections than long-term ones, likely due to the higher consistency in short-term construction processes. It is advisable to review the construction processes to ensure the consistency of the monitoring data before selecting the appropriate dataset.

Port pavements often experience damage, such as differential settlements and cracks, owing to soft ground and heavy equipment operations. This study focuses on developing and applying port blocks in two configurations within a port to assess its applicability based on deflection and settlement characteristics. Falling weight deflectometer (FWD) tests were carried out on both asphalt and block pavements to measure deflection and bearing capacity. Results indicate that the block pavement with a cement-treated base exhibited improved bearing capacity and settlement performance during port operations compared to asphalt pavement. This improvement was evident in the relative deflection and relative bearing ratios, where the cement-treated base demonstrated enhanced bearing capacity over asphalt. Light detection and ranging (LiDAR) measurements revealed several settlements in the crushed-stone base due to surface loads post- construction. While both relative deflection and relative bearing ratios indicated settlement tendencies, the latter proved more consistent with the settlements. The settlements were generally less than 5 cm with the superior bearing capacity block pavement presents itself as a viable pavement for various port settings.

Pre-excavation dewatering (PED) can induce centimeter-level movements in the enclosure wall. Current foundation pit design theory only proposes a calculation method for excavation-induced force and deformation of the enclosure wall based on the elastic fulcrum method, which does not address PED-induced wall deflections. To continue using the elastic fulcrum method for calculating PED-induced wall deflections, it is crucial to determine the distribution of earth pressure on both sides of the enclosure wall during PED. This study aims to propose a novel model for calculating the PED-induced earth pressure on both sides of the enclosure wall. First, we analyzed the shape and influence range of disturbed soil on both sides of the enclosure wall during PED. Then, we explored the characteristics of soil strain distribution in the disturbed zone and proposed a distribution mode for the soil strain. Furthermore, we established a mathematical equation presenting the relationship between the soil strain and enclosure wall deflections, and proposed a calculation model of earth pressure considering the wall deflections during PED. The proposed calculation model accurately reflects the nonlinear relationship between wall deflections and earth pressure during PED. The obtained model, with its simple formulation and easily available data, could provide an important reference for predicting PED-induced enclosure wall deflections.

A circular shaft is often used to access a working well for deep underground space utilization. As the depth of underground space increases, the excavation depth of the shaft increases. In this study, the deformation characteristics of a circular shaft with a depth of 56.3 m were presented and analysed. The main monitoring contents included: (1) wall deflection; (2) vertical wall movement; (3) horizontal soil movement; (4) vertical surface movement; and (5) basal heave. Horizontally, the maximum wall deflection was only 7.7 mm. Compared with the wall deflection data collected for another 29 circular excavations, the ratio of maximum wall deflection to excavation depth of this shaft was smaller due to a smaller ratio of diameter to excavation depth. The wall deflection underwent two stages of deformation: the first stage was mainly circumferential compression caused by the mutual extrusion of joints between walls, and the second stage was typical vertical deflection deformation. The horizontal soil movement outside the shaft was greater than the wall deflection and the deep soil caused great horizontal movement because of dewatering at confined water layers. Vertically, a basal heave of 203.8 mm occurred in the pit centre near the bottom. Meanwhile, the shaft was uplifted over time and showed 3 stages of vertical movement. The surface outside the shaft exhibited settlement and uplift deformation at different locations due to different effects. The basal heave caused by excavation was the dominant factor, driving the vertical movement of the shaft as well as the surrounding surface. The correlation between the wall deflection and the surface settlement outside the shaft was weak.

This paper examines the ring deflection of flexible high-density polyethylene pipe caused by repetitive cyclic plate loading under various burial conditions and relative densities. It also looks at possible mitigation strategies, such as using geosynthetic materials like geofoam to lessen the effects of cyclic vehicular wheel load. Geofoam has a new post-beam arrangement where the post is the vertical support for the beam, and the horizontal capping is the beam. The influence of soil cover thickness, relative density, pipe diameter, geofoam post widths, and beam thicknesses (h) on pipe deflection was compared with the unimproved sand fill scenario. Increasing relative density and cover depth improved the pipe's ring deflection and eliminated the excessive surface settling. Further reduction of more than 60% was achieved with the protective layer of geofoam and brought the over-deflection of the pipe to an acceptable limit. An extensive parametric analysis determined the optimum burial depth and precise location of the geofoam to negate the ring deflection subjected to cyclic loading. Using commercially available finite element software (PLAXIS 3D), a new model was created and validated using experimental results and mathematical solutions derived from the modified Iowa formula. The experimental findings corroborated sufficiently with the numerical and analytical solutions.

Shield crossing the bedrock raised strata easily leads to large deformation of the soil, resulting in deformation and damage of the upper pipelines. To investigate the law of pipeline deformation caused by shield underpassing in bedrock raised strata, the changes in the action range of the additional thrust of the cutter head (p1), the friction resistance of the shield shell (p2), and the additional grouting force (p3) were analysed. A convergence model of the excavation face suitable for bedrock raised strata was proposed. The calculation formula of soil displacement at the axis of the pipeline was derived by using Mindlin's solution and stochastic medium theory. The solutions of the vertical displacement, bending moment and strain of the pipeline were obtained by the energy variational method and the principle of minimum potential energy. Pipeline deformation analysis and reliability verification were carried out by an engineering case in Hangzhou, China. The influence of bedrock distribution and secondary grouting behind the pipe wall on pipeline deformation was studied. The results show that the calculated results are similar to the measured data with a high degree of coincidence, and the degree of agreement is higher compared to the existing method. When the shield tunneling direction is well controlled, the settlement and bending moment of the pipeline caused by the shield crossing the raised bedrock stratum will be reduced, and the reduction increases with increasing bedrock length and intrusion depth. The secondary grouting behind the pipe wall can reduce the settlement of the pipe line, but it is necessary to reasonably control the three parameters of grouting amount per unit length (Vinj), grouting ring length (Lh), and grouting ring angle (delta). Lh should not be too long and can be controlled below 30 m, delta should be controlled within 60 degrees, and Vinj can be adjusted according to the deformation size of the pipeline to prevent excessive or insufficient correction.

Rerounding is a technique for remediating excess deflection in thermoplastic pipe. A pneumatic device vibrates along the vertical axis and pushes against the inside crown and invert to restore the original pipe shape and redistribute the surrounding backfill. A systematic evaluation of the method was justified because rerounding is routinely used by contractors to remediate deflected thermoplastic pipes, and it has not been investigated outside of a few previous reports. Three 900-mm and two 450-mm corrugated high-density polyethylene (HDPE) pipes were installed in various bedding and backfill materials. Test pipes were intentionally installed with substantial deflection (10% or more) and then rerounded. The pipe conditions were measured and monitored by collecting profiles, measuring vertical deflections, and monitoring soil pressure, soil stiffness, backfill characteristics, and pipe corrugation depth before and after rerounding. The data from the deflection, soil stiffness, corrugation, and soil pressure monitoring confirmed the following: (1) during rerounding, soil particles migrated and soil pressure was redistributed; fine material from the crown and springline moved down toward the haunch area, at least in the well-graded aggregate backfill; (2) it is difficult to successfully reduce deflection in corrugated HDPE pipes in well-graded aggregate backfill; (3) installing the pipes with excess deflection proved a significant challenge, as all the pipes required much effort to reach sufficient deflection. It proved necessary to create a device to hold the pipe in a deflected state during backfilling; (4) rerounding successfully reduces deflections for pipes in sand backfill; and (5) test pipes backfilled with Ohio Department of Transportation (ODOT) Type-3 backfill were easy to reround, but a change in environmental conditions and/or dynamic loading may create a change in the stress path leading to excessive deflection and reversal of the effects of rerounding.