Soil Mechanics and Foundation Engineering最新文献

Creep deformation and softening of soft soil foundations under long-term wave loading can cause gravity wharves to experience problems such as excessive settlement, displacement, and sliding, compromising the safety of the wharf structure. In this study, we conduct mechanical index and vibration tests on consolidated and undrained soft soil specimens to analyze the changes in the soil dynamic characteristics with strain under different confining pressures. Subsequently, the dynamic deformation and strength characteristics of the soft soil obtained from triaxial tests are used to develop a finite element model of the wave–gravity structure–soft soil foundation system. Using this model, analyses are conducted by varying the friction angle to simulate the change in the soft soil strength as the number of wave cycles increases. The results are evaluated to investigate the failure mechanism of the foundation and the bearing characteristics of the riprap bed atop the soft soil. The results indicate that the shear modulus of the soil is related to the effective confining pressure and the shear strain; this relationship is fitted using the Van Genuchten equation. As the internal friction angle of the soft soil foundation decreases, its stability decreases nonlinearly, its strength decreases, and its sliding failure surface lengthens. However, simply increasing the riprap layer thickness has a limited effect on the overall wharf stability. These findings will improve the design of gravity wharves founded on soft soils in port areas with intense wave action.

The coefficient of consolidation (Cv) of soft soil is a parameter that reflects the consolidation characteristics of soil under load, but it usually costs a lot in time and money to test. In this paper, an artificial neural network (ANN) and a support vector machine (SVM) are used to establish the Cv prediction model, and the soft soil data of Guigang Beihai Expressway in Guangxi are used to train and test the model. Eleven physical and mechanical parameters of soft soil are statistically analyzed by correlation matrix. Four parameters are determined as input parameters of the calculation model to train and test the calculation model, and the performance and robustness of the prediction model are checked. The results show that the ANN model and SVM model both accurately calculate the Cv, with coefficient of correlation R² > 0.91, root mean square error RMSE < 0.2079 cm²/1000s, and variance ratio VAF > 90%. The prediction accuracy of the ANN model is better than that of the SVM model, and the Monte Carlo simulation results show that the SVM model is most robust. Therefore, the consolidation coefficient is connected with other physical and mechanical parameters, and the ANN model and SVM model are used to predict the Cv, which provides a new idea for fast calculation of the Cv.

When a seismic wave propagates through a bedrock cover discontinuity, mutations in seismic wave propagation characteristics occur owing to reflection and transmission. In this study, based on the medium model and motion equation, the medium of the bedrock and overburden layer slope were connected by boundary conditions, the variation law of the seismic wave reflection and transmission coefficients at the bedrock cover discontinuity were analyzed, and the attenuation characteristics of the energy of the bedrock and overburden layer slope were studied. It was concluded that the transmission coefficients of the P, SV, and SH waves decreased with increasing incident angle. Further, with increasing incident angle, the reflection coefficients of the P and SH waves first decreased and then increased, whereas that of the SV wave first increased and then decreased. When the incident angle was constant, the attenuation of the seismic wave energy by the bedrock cover interface was directly proportional to the attenuation ratio of the interface. Thus, the attenuation of seismic wave energy first increased and then decreased with increasing incident angle.

The paper presents a numerical analytic solution for the calculation of settlement and long-term bearing capacity of a circular foundation on an elastic–viscoplastic base. The work is a development of the previously obtained solution [1] in the elastic–plastic formulation. The Kelvin–Voigt model was used to calculate the volume component of deformation. For the deviatoric component the A. Z. Ter-Martirosyan model was used.

Deep rectangular barrettes are frequently used in tower foundations to resist large axial and substantial horizontal loads. Bi-directional static load tests are widely used as an axial capacity evaluation tool in safe foundation design. This paper articulates the results of a barrette test of 2.80 × 0.80 m in size in the multi-layered soil of Georgia. The maximum applied bidirectional load of 50-m-deep strain gauge instrumented barrette was 51,670 kN. The results indicate a settlement of 8.90 mm at the working load of 25,835 kN and 34.50 mm at the ultimate test load. The shaft resistance and settlement analyses were carried out to understand the geotechnical performance of the barrette in the layered soil. This investigation contributed to a significant, reliable result for the design of the rectangular barrette in multi-layered soil with substantial cost and time savings.

We propose a method for determining the kernel of a deformable foundation model based on the inverse solution of plate bending on an elastic foundation. The results of contact pressure and displacement measurements are approximated by a Gaussian curve, following which the inverse problem for the Fredholm equation of the first kind is solved by the methods of operational calculus using the Fourier integral transform. The solution of the inverse problem represents the kernel of a foundation model, which can be further used to determine deflections and bending moments of beams and plates by solving the corresponding differential bending equation. The obtained model clarifies the distribution and magnitude of the bending moment and eliminates the difficulties arising when solving the elasticity theory problem with a bending moment reduction of 15% or greater.

Coir is a promising natural fiber that can be used for soil stabilization through fiber reinforcement. In this paper, weight gain, reduction in water absorption, and single-fiber tensile strength tests are performed to evaluate the application of different natural agents such as neem oil, kerosene, and cashew nutshell liquid (CNSL) in improving the mechanical properties and durability of coir fibers. Tri-axial tests are performed on soil specimens cured for 3, 28, and 180 days to determine the improvement in their shear strength when reinforced with coir fibers treated with different agents. The fiber reinforcement led to an increase in the shear strength of the soil by improving cohesion and friction angle. Among the different agents used, the CNSL is found to be the most effective agent for coir fiber treatment.

A deep foundation is used to transfer the load of tall and large structures to the underlying soil layers with a sufficient strength. Over the last few decades, a new type of piles has been executed in developed countries using torque with the development of hydraulic devices that can create high torques. Due to the emergence of these deep foundations, the scope of studies in this regard are limited. Thus, studying the behavior of these foundations can increase the breadth of their application in other countries while creating a better understanding of their behavior. In the present research, some models of this type of pile have been created and studied using laboratory equipment and static loading. Execution of drilled displacement and helical piles in the FCV-AUT device as well as running static compression and tension load tests were done according to ASTM D1143 and ASTM D3689 standards. Experiments on the executions have been studied in two modes of density: relative density of 20% to 25% and of 45% to 50%. Accordingly, drilled displacement piles show good performance in terms of compression and tension bearing capacity compared to other piles, while the required installation torque for this pile shows higher values.

Soil improvement is one of the techniques used to reduce the swelling behavior of expansive soil. In this study, highly expansive soil obtained from the site of the new branch of Al-Azhar University in Al-Kawthar city, Sohag government, at a depth of 2.5 m, was used to make a comparison study on the effect of using nano-silica and three different types of granule sand (medium sand, fine sand, and micro sand) on the swelling properties of expansive soil. The swelling properties tests and consistency limits tests for expansive natural soil and swelling soil mixed with 10%, 15%, and 20% of medium, fine, and micro sand and 1%, 1.5%, and 2% of nano-silica were conducted under laboratory conditions. The main results showed that adding nano-silica and ordinary silica particles to expansive soil caused a significant decrease in swelling properties and Atterberg limits. Nano-silica played an important role in improving the swelling behavior of expansive soil.

The cutting blasting project of the Hehui Expressway is close to existing buildings. Vibration reduction measures based on a fine blasting design are put forward to ensure the safety of the project and existing buildings. The project is divided into three blasting areas for construction. This paper investigates “first middle and then edge” and “first edge and then middle” blasting sequences and the vibration responses of adjacent buildings. For the cutting blasting project of the Hehui Expressway, the different blasting sequences are investigated according to the positional relationship between three blasting areas and an existing village, and a reasonable blasting sequence is determined through numerical simulation, on-site blasting tests, and the on-site vibration response data of adjacent buildings. The results show that the existing buildings can be effectively protected by changing the construction sequence of the blasting area on the premise of ensuring the effectiveness and safety of construction. Zone II can be regarded as a huge blasting isolation hole that plays a positive role in the control and attenuation of the blasting stress wave. Blasting in Zone II thus has an excellent vibration reduction effect exceeding 90%. With the adoption of the “first middle and then side” construction sequence, the maximum particle velocity of existing buildings under the action of the blasting stress wave is 1.1 cm/s, which is within a reasonable safety range.