Search

As a new kind of air-hardening soil reinforcement material, polymer is being widely applied in river-bank slope reinforcement and ecological slope protection area. Thus, more attention should be paid to study the characteristics of reinforced soil after immersion. In this study, water-induced changes in strength characteristics of sand reinforced with polymer and fibers were reported. Several factors, including polymer content (1%, 2%, 3% and 4% by weight of dry sand), immersion time (6, 12, 24 and 48 h), dry density (1.40, 1.45, 1.50, 1.55 and 1.60 g/cm3,) and fiber content (0.2%, 0.4%, 0.6% and 0.8% by weight of dry sand) which may influence the strength characteristics of reinforced sand after immersion were analyzed. The microstructure of reinforced sand was analyzed with nuclear magnetic resonance (NMR) and scanning electron microscope (SEM). Experimental results indicate that the compressive strength increases with the increase of polymer content and decreases with the increase of immersion time; the softening coefficients decrease with the increase of the polymer content and immersion time and increase with an increment in density and fiber content. Fiber plays an active role in reducing water-induced loss of strength at 0.6% content.

The studied slope is located in the middle reach of the Yalong River in the eastern margin of Qinghai-Tibet Plateau in Southwest China. A large hydropower station is planning to be built near the slope. Understanding the stability mechanism of the slope is important for dam site design. Under a combination of tectonic activity, unloading and weathering, the bedrock mass was fractured. On the basis of field investigation, the GSI classification system and Barton criterion were introduced to determine the strength of the rock mass. The kinematic, limit equilibrium and discontinuum modeling methods were carried out to comprehensively understand the stability of the slope. The kinematic analyses show that only wedge mode is possible for large rock mass failure. However, limit equilibrium analyses show that both wedge failure and circular slip are not expected for rock mass. The slope rock mass is now in the surface rebalance stage. The potentially unstable part is the covering deposit. The 40 million m3 surface deposit is now nearly in a limit equilibrium state. The possibility of failure reaches 41%. Mitigation measures must be put into effect on the deposit to assure the stability of the slope. The results indicated that the failure mechanism of the slope was not controlled by the discontinuities in the rock mass at present but depended on the stability of the surface deposit.

Vegetation has good application in slope stabilization, but its beneficial effects on reinforcing topsoil are generally limited by the soil properties it was cultivated in. This study aims at evaluating the strength improvements of sand-root composite by treating with polyurethane polymer and hence investigating the mechanism of polymer-root-soil interactions. Vegetation roots were selected and mixed with dry sand and polymer solution to prepare remolded specimens. A series of experimental tests were then performed at different percentages of root content (0, 0.4, 0.8, 1.2, and 1.6 % by weight of dry sand) and polymer content (1, 2, and 4% by weight of dry sand) to evaluate the shear parameters and unconfined compressive strength (UCS). The combined mechanism was studied by scanning electron microscopy (SEM) images. The results showed that the strengthening effect has greater efficiency with higher polymer content. Through varying contents of vegetation root, it was found that low root content induced an undesirable weakening effect on the strength of the treated soil. However, this situation was somewhat improved with the increase in root content. The good flexibility of polymers not only promote the capacity of soil to energy absorption, but also impart good ductility to soil. The presence of polymers greatly strengthens soil stability due to its special network structure, by which the improved shear resistance at the root-soil interface provides sufficient anchorage effect for the tensile strength of roots to be fully mobilized. Overall, the synergistic effect of root reinforcement and polymer treatment has the potential for its use in soil stabilization.

A considerable number of engineering hazards are caused by loose internal structure of sands. Thus, many researchers have explored a variety of reinforcement methods. A new reinforcement technique was experimentally evaluated in this study. In particular, a hybrid method with a combination of fiber and polymer was studied. Three different types of fibers (sisal, polypropylene, and palm) in combination with varying concentrations of polymers were experimented to improve the internal structure and strength of sand samples reconstituted at different densities. Through a series of laboratory tests, the compressive and tensile strength variations of different combinations were obtained, and the interaction between fibers and polymer inside the sand was evaluated by scanning electron microscopy (SEM). The experimental results show that the tensile and compressive strength of the reinforced sand increases with the increase of the polymer concentration, sample density, and different fiber combinations. This provides some references for future practical engineering applications.

Anaerobic digestion (AD) has been widely applied for treating organic waste and is known as a carbon-offsetting process. However, most studies relied on laboratory-scale experiments or literature to calculate carbon emissions from AD process, and the impact of digestate processing was overlooked. This study assessed the carbon footprint for an industrial food waste co-digestion plant with operational data. The results indicated that carbon emission before digestate treatment is -88.5 ± 4.4 kg CO

This study focuses on the shear-strength properties of polyurethane polymer–treated sand stored at different temperatures. The triaxial test was performed at unconsolidated and undrained co...

Prefabricated vertical drains (PVDs) were used in accelerating the consolidation process of a soft soil foundation in the lower reach of the Yangtze river. Field monitoring was carried out during the embankment construction. The settlement, lateral deformation and pore pressure of the soft foundation were collected. The consolidation was also predicted with a coupled mechanical and hydraulic plane strain finite element model. The results indicate that the consolidation process of soft ground followed the loading steps. The PVDs can efficiently reduce the excess pore pressure in the soft ground and shorten the consolidation period. The pore pressure in the PVD reinforced zone is less than 20.0 kPa at the end of the construction in contrast to 52.0 kPa for unimproved foundation. The excellent drainage capacity of PVDs is useful in improving the shear strength of soft ground. Deformation form of the improved foundation is mainly the settlement and the lateral displacement at embankment toe is less than 9.0 cm. Stability analysis shows that the foundation is more stable during the construction with a factor of safety more than 1.20. Research results prove the feasibility of PVD technique in improving the soft ground in the lower reaches of the Yangtze river.

This paper presents a finite element analysis on a soft embankment foundation improved by prefabricated vertical drains. A plane strain analysis was performed using equivalent permeability. The predictions of settlement, pore water pressure, and lateral displacement were compared with the available field measurement data, and a general fair agreement was observed. Numerical results indicate that the settlement below the left part of the embankment is obviously larger than that of the right part. The maximum settlement occurs below the left shoulder of the embankment and reaches 1.26 m. The entire shallow foundation shows a movement trend to the left toe. The designed left embankment shoulder was suggested to be 0.16 m higher than the right side. Monitoring and simulation results demonstrate that the foundation is stable during the construction. The factor of safety at the end of the final loading stage is about 1.81. The performance of the embankment is consistent with the design prescriptions, confirming the effectiveness of the soil improved technique included in this project.

Landslide developed in rock mass usually has irregular shear plane. An approach for calculating distributed factor of safety of the irregular shear plane was put forward in this paper. The presented method can obtain not only the detailed stability status at any grid node of a complex shear plane but also the global safety of the slope. Thus, it is helpful to thoroughly understand the mechanism of slope failure. Comparing with the result obtained through the limit equilibrium method, the presented method was proved to be more accurate and suitable for stability analysis of rock slope with a thin shear plane. The stability of a potentially unstable rock slope was analyzed based on the presented method at the end of this paper. The detailed local stability, global stability, and the potential failure mechanism were provided.

In this study, the mechanical behavior of a polyurethane (PU) polymer-sand mixture was investigated by performing a series of uniaxial compression (UC) and direct tensile (DT) tests at different polyurethane polymer contents (PUC), dry densities (DD) and temperatures (TP). Results show that the axial stress–strain relationship depends on PUC, DD and TP, in particular, the failure mode gradually changes from fragile to ductile feature; the uniaxial compressive strength (UCS), secant modulus (E50) and tensile strength (TS) all linearly increase with increasing PUC and DD at different TPs. Positive and negative temperatures (i.e., 35℃ and 50℃, −20℃ and − 10℃) both make positive effect on PU treatment since the UCS ratio, E50 ratio and TS ratio all are higher than unity. Positive temperature significantly increases the strength and ductility, while negative temperature obviously affects the strength and modulus. Linear relationships of E50-UCS, UCS-TS are obtained, and these relationships depend on temperature. Scanning electron microscope (SEM) observation reveals that the presence of PU additive links adjacent grains together, improving the mechanical properties of the mixture. As this bonding effect is expected to be dependent on PUC, DD and TP, the strength, ductility and stiffness are different in different scenarios.

Polyvinyl acetate constitutes a class of polymers that can entirely dissolve in water to form a solution. In this study, polyvinyl acetate as a nontraditional chemical stabilizer was used in soil improvement. Laboratory tests were carried out to evaluate the effect of polyvinyl acetate on swelling-shrinkage properties of expansive soil. A series of shrink/swell tests were performed with adding polyvinyl acetate as amendment at a concentration 3 g/cm3 to four aggregate sizes in the range of 0–0.5 mm, 0.5–1 mm, 1-2 mm, and 2–5 mm and five concentrations 1.5 g/cm3, 3 g/cm3, 4.5 g/cm3, 6 g/cm3, and 9 g/cm3 to soils with aggregate size in the range of 0.5–1 mm for comparison of results with those of untreated soils. The results show that all the linear swelling ratio (LSWR) and linear shrinkage ratio (LSHR) values of the treated specimens decrease. SEM images and the test results indicate the achieved reduction in volume change of the soil tested using soil pore filling and particle encapsulation.

This study focused on investigating the effects of polypropylene fiber on the liquefaction resistance of saturated sand. We performed a battery of tests with a state-of-the-art ring shear apparatus on fiber-reinforced saturated sand, considering the influences of fiber content and sand density. Two different shearing methods named shear-torque-controlled (STC) and cyclic-torque-controlled (CTC) were considered for carrying out the tests. An energy approach was chosen to evaluate the results, and the fiber reinforcement mechanisms were analyzed. Our test results showed that in STC tests, the shear strength and shearing time of saturated sand increased proportionally to an increase of fiber content and sand density. The cycles required for liquefaction in CTC tests also increase with an increase in sand density and fiber content. The presence of fibers clearly increases the shear energy required for liquefaction. The shear energy increases with an increase in sand density and fiber content. Greater total shear energy is required in specimens with a higher density or larger fiber content. Fiber reinforcement in sand has acted as a spatial network in interlocking soil grains, thereby resulting in the necessity of more energy for overcoming the resistance during the shearing process. After performing the shearing test, the unreinforced specimen with loose structure collapsed totally, and the one with a dense structure collapsed partially, while fiber reinforcement specimens still maintained structural stability.

Sand as a building material is pretty common in engineering constructions such as slopes and foundation pits. The great instability is generally generated because of the lack of cohesion inside and such instability is more serious during rains or when subjected to excessive external loads. This paper is aimed to study a combination of polyvinyl acetate polymer and sisal fiber as reinforcement materials. The focus of this study is to determine the effects of polymer content, fiber content, and dry sand density on the improvement in mechanical behavior of reinforced poorly graded sand. A series of direct shear, unconfined compression, and tensile tests on the reinforced sand have been conducted. The results suggest that the reinforcement effect increases with dry sand density up to 1.55 g/cm3 and then levels off. For fixed dry sand density, the strength of the improved sand enhances with the augment of polymer and plant fiber contents. At maximum contents, the reinforced sand can have 480 kPa of shear tensile strength, 1,276 kPa of unconfined compressive strength, and 240 kPa of tensile strength. The reinforcement mechanisms are revealed by Scanning Electron Microscope images. Polymer forms firm the polymer–soil matrices that enhance the fiber–sand interactions to mobilize tensile stresses. The combined use of polymer and fiber is preferred in engineering practices because of its zero negative impacts on the environment.

Imbalanced classification is a classification problem that violates the assumption of uniform distribution of samples. In such problems, traditional imbalanced datasets are measured in terms of the imbalance of sample size, without considering the distribution information, which has a more important impact on the classification performance, so the traditional measurements have a weak relation with the classification performance. This paper proposed an improved measurement for imbalanced datasets, it is based on the idea that a sample surrounded by more same class samples is easier to classify, for each sample of different classes, the proposed method calculates the average number of the k nearest neighbors in the same class in different subsets under the weighted k-NN, after that, the product of these average values is regarded as the measurement of this dataset, and it is a good indicator of the relationship between the distribution of samples and the classification results. The experimental results show that the proposed measurement has a higher correlation with the classification results and shows the difficulty of classification of data sets more clearly.

Detailed engineering geological studies and stability assessments were carried out on Xiari rock slope in southwestern China. Geomorphic analysis of digital elevation models, detailed structural field mapping and boreholes data indicate that the slope has a poor rock mass quality and complex deformation mechanism. The necessary rock mass parameters were determined by means of slope mass rating (SMR), geomechanic classification system (Q) and geological strength index (GSI). Slope stability analyses were performed by means of kinematic, limit equilibrium and numerical modeling techniques. Analyses results indicate that slope stability is mainly controlled by the discontinuities. The combination of discontinuities and topography makes the slope susceptible for a large landslide. The major potential mode of slope failure is planar failure. Planar failure has a higher probability in comparison to wedge failure, while wedge failure contributes towards a more severe hazard, like the landslide in part A of the study area. Numerical analysis results indicate a catastrophic landslide in the future, with a volume estimated to be more than 2.5 × 106 m3.

Earthquake-induced liquefaction is one of the major causes of catastrophic earth dam failure. In order to assess the liquefaction potential and analyze the seismic performance of an earth dam in Fujian, Southeastern China, the in situ shear wave velocity test was firstly carried out. Results indicate that the gravelly filling is a type of liquefiable soil at present seismic setting. Then the effective stress model was adopted to thoroughly simulate the response of the soil to a proposed earthquake. Numerical result generally coincides with that of the empirical judgment based on in situ test. Negative excess pore pressure developed in the upper part of the saturated gravelly filling and positive excess pore pressure developed in the lower part. The excess pore pressure ratio increases with depth until it reaches a maximum value of 0.45. The displacement of the saturated gravelly soil is relatively small and tolerable. Results show that the saturated gravelly filling cannot reach a fully liquefied state. The dam is overall stable under the proposed earthquake.

To binary problems, class-imbalanced data are defined as datasets in which the instance number of two classes is extremely different. Classifiers based on undersampling and oversampling were proposed to solve the class imbalanced problems. Techniques based on ensemble of classifiers has been successful for class imbalance problems. In this paper, we proposed an ensemble based approach EHSBoost. EHSBoost is based on EUSBoost, which combines the EUS with Boosting algorithm. The goal of our proposed algorithm is to take advantage of undersampling and oversampling. We consider the usage of hybrid sampling in a supervised manner to improve the accuracy of the weak learner. We have conducted experiments on 16 datasets. These datasets are from the KELL data repository. Three evaluation metrics are used to evaluate the proposed method and the state of art counterparts. Experiments show that, the proposed ensembles algorithm based on evolution hybrid sampling method has significant advantage over other methods for classification of class imbalance datasets.

Mahe colluvium, located in the middle reach of the Yalong River valley, is about 3.5 km upstream of the proposed Lenggu dam site. About 125 vertical meters of the deposit will be immersed in the damming water during the operation of the Lenggu Hydropower Station, which could greatly reduce the stability of the colluvium. The consequent landslide (up to 13 million m 3 ) would be a major threat to the infrastructure of the station. Subsurface investigations indicate that the main colluvium consists of three units: the thicker upper and lower units and a thinner middle deposit. Grain size distribution analysis indicates that the content of coarse materials increases with depth, and the deposit most likely functions as a surficial fine material layer and an underlying coarse material layer. Stability analyses, including the deterministic and probabilistic analyses, show that the entire colluvium deposit is more stable during dry conditions. But the surficial fine material layer has a large possibility of instability (with probability of failure ranges from 22.2 percent to 26.2 percent) even though the deterministic factor of safety is above 1.0. Stability analyses on an impoundment model indicate that pore-water pressure can produce noticeable reduction in slope stability. Under the impoundment scenarios, both deterministic (with factor of safety of

It is important to develop a communication-efficient solution to manage data distribution modeling in an environmental sensor system supported by a clustered structure of the network. Thus, sensor networks present significant systems challenges involving the use of large numbers of resource-constrained nodes operating essentially unattended and exposed to potential local communication failures. MEMS technology, more reliable wireless communication and low-cost manufacturing have resulted in small, inexpensive and powerful sensors with embedded processing and wireless networking capability. When the number of sensor nodes becomes large, the centralized approach must be reviewed. In this paper we discuss the strengths and limitations of localized and collaborative methods in supporting services and applications of sensor networks in the life-science.