Based on the monitoring data of settlement during construction, two parameters of GM(1,1) model are determined using genetic inverse analysis method and least square method respectively. Then, the later settlement at any time and last settlement can be predicted. Application of genetic algorithm in back-analysis of parameter for predicting settlement of high embankment has a higher precision than other methods in comparison with the monitoring data and it is suitable for predicting the settlement of high embankment. Therefore, the method proposed here is practical and valuable.
Aimed to the fracture behavior before peak load, the rock fracture stability determined by fracture curves after peak load has been studied. Meanwhile, the concept of crack propagation curves and rock fracture specimen model to explain the crack and elastic body was proposed. With this model, the fracture curves and influence factors for rock fracture specimens have been investigated experimentally.
The study investigated the reinforcing effect of vetiver root on soil by conducting outdoor planting tests and indoor root tests. The cracking indexes of soil specimens with varying root contents were analyzed, and a statistical model was established to determine the relationship between the cracking indexes, the number of dry and wet cycles, and the root content. The study revealed the crack evolution law of vetiver-reinforced expansive soil. The study explored the mechanism of the vegetation root in inhibiting the cracking of expansive soil and determined the optimal planting density of vetiver grass through outdoor planting tests. The results indicate that: The surface crack rate (CR), total crack length (CL), and crack number (CN) in the root-soil specimen exhibited exponential growth with an increase in the number of wet and dry cycles. This growth was more pronounced during the first and second cycles. The vetiver root could effectively reduce soil crack formation, and the specimen's cracking resistance is positively correlated with the root content. With the root content increased, the CR, CN, and CL decreased. The logistic model is suited to the CL of added root soil. The logistic model is more suitable for the growth model of the CR of the expansive soil with low root content, while the Boltzmann model is more suitable for the growth model of the CR of the expansive soil with high root content. Width of crack (CW) is better suited to the DoseResp growth model. The Boltzmann model is more applicable to the CN in expansive soils with low reinforcement, while the logistic growth model is more suitable for the development of CN above 0.21% root content. The development of the crack network was influenced by two key factors: the root content and the number of wet and dry cycles. Under the condition of planting roots, the development of crack networks in expansive soil differs from that of expansive soil with added roots, and there is no clear pattern to follow. The inhibitory effect of the vetiver root on cracking of expansive soil is related to the planting density of vetiver.
The expansive soil slope is mainly characterized by the decline of slope integrity caused by shallow expansive soil cracking and the destruction of internal soil structure, which seriously affects the overall stability of expansive soil slope. To study the effect of the combination of geogrid reinforcement and slope vegetation on inhibiting the development of expansive soil cracks, six groups of test models were made. The natural dry-wet cycle was simulated, and the crack image was binarized by using image processing technology. The crack characteristic parameters such as crack ratio, crack width, and crack length were extracted, and the effect of various reinforcement methods on inhibiting the development of cracks was comprehensively evaluated. The basic situation of the development of crack indexes in each group with the development of multiple dry-wet cycles was obtained, and the fluctuation changes of crack indexes in different stages were different under different reinforcement methods and dry-wet cycles. At the same time, the influence of different reinforcement methods on the crack development of expansive soil is obtained. It is considered that planting vetiver grass + geogrid backpacking has a good effect on inhibiting the crack development of expansive soil.
Considering the practice of embankment construction,the experimental device and experiment method to prepare experimental samples with different compactnesses to measure water permeability of sands soils or clay under compressive load changes was manufactured.According to the measurement of variations of water permeability under compressive load or unload in different compactnesses,the rule of water permeability of sand soil was revealed due to be influenced by different compressive loads and different compactnesses.It is shown that the compressive load and compactness both influence the water permeability of the sand soil greatly;but the factor of compressive load influences,its water permeability more greatly.Especially for the low compactness soil,the influence of the load on the permeability is very obvious.
Based on elastic theory,the differential settlement reduction mechanism by geosynthetic inclution was analysed and the method to predict the best placed depth of geosynthetics was presented too.
Aluminum (Al) is known to inhibit plant growth and limit crop yields in acid areas.This study aimed to investigate the effect of endophytic fungus Glomerella sp.JP4 infection on the growth, photosynthetic pigments, antioxidant enzyme activities, organic acids contents, and Al content of endophyte-infected rice seedlings (EI) and endophyte-uninfected rice seedlings (EF) exposed to Al stress for 9 days.Al stress decreased shoot height, root length, and dry weight of EF plants.Endophyte infection increased the growth parameters except for root length.Compared to EF plants, the chlorophyll a+b content and carotenoid content were significantly enhanced in the EI plants.Antioxidant enzyme activity was also increased in the EI plants compared to the EF plants subjected to Al stress, while malondialdehyde (MDA) content was remarkably reduced.Endophytic infection significantly increased the contents of citrate and succinate in leaves, as well as that of lactate, malate, fumarate, and succinate in roots under Al stress.Endophyte infection decreased the Al content in the shoots and the roots and restricted the Al transfer from the roots to the shoots in the EI plants compared to the EF plants.Our results indicated that infection with endophytic fungus JP4 in the roots had an active role in promoting plant growth, alleviating the phytotoxic effects caused by Al exposure.
To simulate the field conditions of a partial-cut and partial-fill embankment, the 3D non-linear finite difference model (FLAC3D) was utilized in this study. FLAC3D is able to visualize and characterize the deformation characteristics and stress distributions. The material parameters were determined from the laboratory tests and knowledge of the site conditions. The analysis results demonstrated that one of the main contributing factors for the settlement is the backfilling thickness as the settlement tended to increase with the backfilling thickness. Also, the maximum differential settlements existed in a small region (about 1.5 meter wide) at the junction of partial-cut and partial-fill embankment. Field evaluations on many expressways have also confirmed that surface cracks often occur in this small region. Transportation authorities can benefit from this study by formulating initiatives to develop cost effective design and construction methods that minimizes cracking, with a focus on the ∼1.5 meter wide region.
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