The Northwest Loess Plateau in China is mountainous and contains deep valleys which consist mostly of loess. Tunnels constructed in such deep valley and backfilled with soil are called high-filled cut-and-cover tunnels (HFCCT). Several studies have been conducted on HFCCT, but the creep behavior of loess backfill has not been fully explored. Post-construction settlement in loess is large, and it is difficult for stability to be reached in a short time. Therefore, it is necessary to predict long-term behavior of earth pressure around an HFCCT to ensure long-term safety. The primary purpose of this paper is to investigate changes in earth pressure and displacement of soil with time after the completion of the backfill process. This is achieved using FLAC^3D software (finite difference method). The results show that discrepancies in soil settlement and surface settlement will gradually increase and eventually reach stability. The distribution and value of earth pressure also becomes redistributed. Meanwhile, influencing factors such as slope angle and valley width gradually weaken with time, and only affect the time needed to reach stability.

The effect of ladle furnace slag or LFS on the mechanical properties of the lateritic soil mixes for use as a subbase course material in the pavement structure was investigated. The lateritic soil grade E with the lowest mechanical properties was studied by mixing the LFS in the ratios of 5 to 12 wt%. The pavement material criterion of the Thailand Department of Highways was used to qualify the liquid limit, plasticity index, the California bearing ratio, and the swelling index of the mixed lateritic soil with the LFS. An increase in the California bearing ratio of the lateritic soil under the soaked condition was found to be positively correlated with the increasing LFS. Meanwhile, the liquid limit and the plasticity index decreased, leading to a decrease in the swelling index of the lateritic soil containing LFS. Using LFS reduced the total fine-particle ratio in the soil mixture but effectively enhanced the degree of compaction and swelling tolerance in the lateritic soil mixture. 10 wt% LFS is strongly recommended as a minimum admixture in the lateritic soil due to the highly improved plasticity and the mechanical properties of the lateritic soil for a subbase course material selection under the standard specifications.

The excess pore pressure increases under undrained cyclic loading which cause decrease in effective stress followed by possible failure in the soft soil. With the inclusion of vertical drains radial drainage allows quick dissipation of excess pressure during cyclic loading and thereby failure of foundation soil may be avoided. The present study aims for analytical closed-form investigation on soft cohesive deposit under radial flow consolidation through vertical drains with no smear when subjected to long-term rapid cyclic loading. The mathematical formulation of pore pressure including degree of consolidation under cyclic loading is developed by using Green's functions technique. Results obtained from the proposed formulation are in good agreement when compared with published field data which confirms its correctness to predict consolidation under cyclic loading. Once the proposed model is validated, it is applied to investigate the effect of vertical drains on variation of pore pressure ratio with number of loading cycles. The findings indicate that the pore water pressure generates slowly at the outermost boundaries of the vertical drains for initial number of loading cycles. The magnitude of pore water pressure accumulation increases and then dissipates for higher number of loading cycles. The variation of degree of consolidation for different frequencies of a unit cell of a prefabricated vertical drain is also furnished.

There exists large volume of marine dredged clay generated worldwide to potentially compromise to ocean environment. Efficient resource utilization of dredged clay is crucial to sustainable development of offshore works. In this study, cement-treated marine dredged clay is suggested as filling materials for the construction of artificial islands in Dalian Bay, China. To evaluate influence of cement addition on compressibility, a series of oedometer tests were performed on reconstituted and cement-treated dredged clay. The effects of initial water content, cement content and curing time were examined. In addition, the pore fluid salinity effect on reconstituted and cemented dredged clay was explored by desalination treatment, respectively. The testing results show that the vertical yield stress of cemented dredged clay is governed by initial water content while the compressibility in post-yield state is determined by cement content. The influence of curing time is more significant for the specimens with higher initial water content. The compressibility of reconstituted dredged clay decreases when increasing salinity of pore fluid, but pore salt accelerates the degradation of artificial structure of cemented clay. Moreover, a practical predicting method was presented based on the experimental data. Both the pre-yield compression index Cs and post-yield compression index Cc are correlated with the yielding point. The proposed method enables to more quickly capture the compression curves of cement-treated dredged clay in practice.

Under compression, the flaws in soils will not only weaken the mechanical properties of soils, but also affect the strain localization of soils. In order to study the influence of flaws on the behavior of soils under compression, the uniaxial compression tests of clays with different inclination and position fissures were carried out, and the two-dimensional numerical analysis was also discussed based on the damage plasticity model. Analyzing the results of the uniaxial compression test and simulation of the intact and fissured clays, the following conclusions can be drawn: (1) The 60-degree fissure located on the upper position of the right edge of the clay has the greatest influence on the failure form and damage energy of clays, which can reduce the compression strength by 30% compared with that of the intact clay. (2) The numerical method based on the damage plasticity model can basically simulate the compression behavior of clays containing a pre-existing fissure and reproduce the failure characteristics of clays. (3) The preset fissure has obvious influence on the evolution of maximum principal stress in the area with serious damage, but less on the shear stress. And in the area with slight damage, the effect on the maximum principal stress and shear stress is very weak.

Arching effect is a universal phenomenon of the load transfer mechanism which is visually observed in the heaps of granular material. In this study, we adopt geometrically non-linear isogeometric finite element analysis to revisit the theoretical concept of the arching effect in the granular sand piles under base deflection with an assumption of elastic continuum theory. Through two studies of the planar and conical sand heaps, this work expects to supply the numerical results for double-checking some simple benchmarks before extending to the complicated problems. Herein, the reliability and accuracy of the present model are validated by checking the weight balance condition and comparing with some available literature. The numerical results demonstrate that the stress dip accompanying a significant shear stress mobilization at the base is formed immediately once the base deflection occurs. Furthermore, the trajectories of principal stresses are plotted to visually manifest the force propagation in the sand piles which enables us to explain the formation and shape of the arching effect.

More and more attention is paid to the stability, safety and comfort of trains during its operation stage. When the train is running, in addition to the track gravity, it is also affected by the train load and earthquake, these dynamic effects will have a certain impact on the normal operation of the railway. However, the current research on the dynamic response of composite CFG and cement-soil compaction piles foundations under dynamic loads is rarely involved. Taking the composite foundation of Baoji-Lanzhou Passenger Dedicated Line as the research object, the dynamic response of the composite foundation under train load, seismic wave and train-seismic load is analyzed in detail by using numerical simulation software. The results show that under the train load, the maximum displacement occurs at the action position of the train load, and it is gradually reduced downward. The overall displacement is not large, and the influence on the operation of the train is little. Under earthquake action, the displacement is the largest at the bottom of subgrade, and gradually decreases upward, which has little effect on the top of embankment. Under the train-earthquake action, the displacement of subgrade bottom and embankment top is larger, and gradually decreases to the middle. It provides the corresponding theoretical basis for the same type of railway subgrade engineering.

Under the effect of load and seasonal rainfall, the disintegrated carbonaceous mudstone (DCM) softens and further disintegrates, causing large settlements and even collapses of the DCM embankments. For this reason, some treatments should be taken to improve the engineering performance of the DCM. In this study, four materials including sodium alginate (SA), calcium chloride (CaCl₂), bentonite and nano-Al₂O₃ were jointly used as modifiers to treat the DCM. The influences of each modifier component on the unconfined compressive strength (UCS), cohesion, angle of internal friction, and coefficient of permeability of the DCM were examined by unconfined compression tests, direct shear tests and permeability tests. The results demonstrated that with the addition of modifiers, the UCS, cohesion and angle of internal friction of the DCM are enhanced, whereas the coefficient of permeability is reduced. The sensitivity analysis showed that the dosage of SA is the dominating factor affecting the engineering performance of the DCM. Thus, special attention should be paid to the dosage of SA when improving the DCM. On the other hand, bentonite is the least important factor for most of the examined engineering properties among the four modifier components. An UCS value that is greater than 1500 kPa was selected as the evaluation criterion, and the stress-strain relationship and failure mode of each sample under unconfined compression were examined. On this basis, eight groups of satisfactory mixing ratios were obtained for the modification of the DCM. It is suggested that when designing mixing ratios of modifiers for the DCM, the recommended SA/DCM ratio is 4%-6%, but the quantities of CaCl₂, bentonite and nano-Al₂O₃ can be adjusted according to the needs and costs.