Scrap Tire Derived Geo-Materials (TDGM) mixed with soil are often being used as environmentally friendly granular materials in sustainable construction of civil engineering projects for reducing dynamic loads acting on geo-structures and soil liquefaction remediation purposes. Predicting dynamic properties of TDGM-soil mixture is a complicated task due to the numbers of factor involved in soil- TDGM mixture. This study presents application of artificial intelligence technique in estimating dynamic characteristics of granular mixture of Gravel and Tire chips (GTCM). Support Vector Regression (SVR) and Artificial Neural Networks (ANN) were used for predicting shear modulus and damping ratio of GTCM. Shear modulus and damping ratio models were developed using ANN and AVR techniques. The models were trained and tested using a database that included results from a set of laboratory tests on the GTCM. Stress controlled cyclic triaxial tests were conducted on specimens of gravel and tire chips with different volumetric portions of gravel in mixture (GF). The tests were performed on GTCM specimens at an initial relative density of 50% under different initial effective confining pressures. Test results have shown that shear modulus and damping ratio of the granular mixtures are remarkably influenced by volumetric fraction of gravel in GTCM. Furthermore, shear modulus was found to increase with the mean effective confining pressure and gravel fraction in the mixture. It was found that a feed-forward multilayer perceptron model with back-propagation training algorithm have better performance in predicting complex dynamic characteristics of granular mixture than SVR one.
The test embankment using granulated blast furnace slag (GBFS) was constructed in 2001, and its long-term characteristics were investigated. In this study, a sampling was conducted at the embankment after 16 years passed from construction, physical, chemical and mechanical properties were examined by field measurement and laboratory tests. Conclusions of this study are obtained as follows: 1) The dry density of the GBFS indicated about 1.2 g/cm3, and it was confirmed that the lightness of embankment was maintained. 2) The unconfined compressive strength shows more than 1 MPa by the hydraulic property of GBFS. 3) A high pH was observed directly under the embankment. But at other points, the pH showed near neutrality, and it is considered that there is no influence on the surrounding area.
An examination was performed on the use of soil-cement mixing walls, which have been treated previously as temporary structures left buried in the ground as permanent piles in order to rationalize foundation structures and to reduce environmental burdens. The construction machinery used to build temporary structures using such walls was used to construct the soil-cement mixing wall in this study, and the range for the strength of the soil-cement was assumed to be in the commonly adopted range (500 to 2000kN/m2). The vertical bearing capacity of the soil-cement mixing wall where the embedded portion is used as a permanent pile was examined by hypothesizing two types of failure modes: failure of the ground and sliding failure between the soil-cement and the H-shaped steel surface. This study aimed for the use of the embedded portion of soil-cement mixing wall as a permanent pile and evaluated the vertical bearing capacity in a full-scale load test and a model load test. This study first describes the background and the previous studies; second, it indicates the full-scale load tests in order to evaluate the bearing capacity of the soil, then presents the model experiments to estimate the bearing capacity on the pile body, and finally discusses the evaluation method of determining vertical bearing capacity on soil-cement mixing pile.
Recently, in addition to cohesive soils, geosynthetic clay liners (GCLs) are used for repair of small earth dams as a water barrier. In previous research, full-scale shaking table tests were carried out for four types of embankments under different installation conditions of GCLs in order to estimate their earthquake resistance. This paper firstly reviewed the previous studies and also have examined the deformation characteristics of embankments with GCLs based on 3D laser scanning. As a result, the deformation of the upstream side of embankments was greater than that of the downstream side in all cases. As for the post-earthquake performances, it is essential to avoid overflow after earthquake, and it has been suggested that GCLs should be set within width of crests as possible to retain the crest height at the downstream side.
In late years, it may use in combination deep mixing method and shallow mixing method for the purpose of cost reduction in the soft ground measures of road embankment. When we thin thickness of shallow improvement layer and combine it with the deep mixing column of the low improved rate, tensile stress occurs in a base of shallow improvement layer. The specimen and the adhesion method with the testing equipment become important to perform a tension test of the improved soil. In addition, it is important to make a homogeneous specimen so that local weak parts do not affect the test results. Therefore, three types of soil were used to make an improved soil, and unconfined compression test and unconfined tensile test were performed. We mixed solidification materials to three kinds of ground materials and made solidification materials improvement soil and carried out one axis compression examination and one axis tension test. In this report, In this report, we report the result of examining the method of compacting the specimen to the soil improved by solidifying material and the method of preparing the mixed sample to make a homogeneous specimen.
In this study, the effect of physical and chemical properties on the long term mechanical property of surplus soils improved by lime and cement was investigated by conducting unconfined compression and needle penetration tests on the specimens cured under different conditions. The conditions of curing were set as sealed with plastic wrapping and soaked under pure and acidic water, respectively. As the result of the experiments after about 6 months (168 days) from specimen preparation, effect of soaking on the strengths appeared obviously in the cement treated soil. The unconfined compressive strengths of the soaked specimens were found to be the smallest, while those of the sealed specimens were the largest. It was suggested by the needle penetration resistance that local deterioration progressed gradually from the surface of the soaked specimens. It was inferred that these differences in the strengths between sealed and soaked curing were caused by the changes in physical properties such as degree of saturation, and chemical properties due possibly to the leaching of hydration products during soaked curing.
This report describes the deformation processes of the soft-ground embankment following the simulated seismic motion and the effect of the composite ground improvement technique to prevent deformation of the embankment and its surrounding foundation. This preliminary study was conducted with the aim of making recommendations for soft-ground embankment design resistant to earthquakes. Thought the result of the dynamic centrifuge model tests, we verified that the gravel foundation was effective in significantly reducing a settlement of the embankment crown and a deformation of the surrounding ground when subjected to simulated level-2 seismic motion.
Foam agents used for a method of rheological foam shield-tunneling are mainly comprised of anionic surfactants which are toxic to fish. According to the previous studies, the foaming agent in soil mixed with the foam can be evaluated that environmental impact of toxicity is small because that is inhibited elution from soil mixed with foam and is reduced by biodegradation after elution. In this paper, we analyzed assuming disposal site at sea based on parameter obtained by the previous test results and studied the environmental impact of the foam agent. As a result, elution of foaming agent out of the disposal site and elution concentration of foaming agent in the disposal site were sufficiently small, and concentration of the foaming agent degreased at time. As an environmental impact assessment, the amount of maximum elution was estimated to be sufficiently small, 1/100 or less, compared to the predicted no-effect concentration calculated from acute toxicity. It is possible that we evaluate the environmental impact of soil mixed with the foam by analysis based on test results.
Soils excavated in construction works often contain non-anthropogenic heavy metals and metalloids due to their geologic histories. Evaluation of their leaching behaviors is essential to predict the environmental impact and achieve an optimum design when reusing such soils as construction materials. However, applicability of the conventional column leaching test to soils containing non-anthropogenic substances is uncertain, since their chemical forms and leaching processes are different from those in contaminated soils. Also, the column size is one of factors influential to the leaching behavior. This paper addresses the leaching behaviors of arsenic (As) and other inorganic constituents contained in a marine sediment by employing two different-size column percolation tests (50 mm in diameter × 300 mm in height and 150 mm in diameter × 700 mm in height) with saturated/unsaturated flow conditions. Long term leaching profiles were analyzed to assess the effects of specimen size and flow conditions. At the middle of the unsaturated larger column, higher As leaching concentrations were observed under neutral condition. However, As leaching was limited at the bottom due to precipitation of As with co-precipitation of iron and aluminum compounds. As a result, there was no significant difference in both As leaching amount and leaching processes obtained in two column percolation tests.
Environmental conservation and post-closure land use are important considerations in coastal MSW landfills. A system consisting of a drainage layer and thick soil cover installed over an entire waste layer is proposed as an effective measure for the containment of waste leachate and post-closure land use in this study. The effectiveness of such a system having drainage layer and thick soil cover was evaluated via laboratory experiments and numeral analysis. Laboratory experimental results indicated that water discharged through the drainage layer is maintained at low concentration and is therefore expected to achieve satisfactory quality simulated using electrical conductivity as an index, as waste leachate can be properly contained in the waste layer due to the performance of the drainage layer. The experimental results also showed that this performance is not significantly deteriorated even due to several types of obstacles, such as discontinuity of drainage layer, pile installation, etc., which are anticipated at the actual landfill site. The proposed system is expected to perform satisfactorily in terms of leachate containment and post-closure land use.
Injecting the improvement material into the ground by the chemical solution injection method, the permeability of the ground decreases due to the occurrence of clogging in void of ground. The permeability of the ground greatly affects the penetration range of the chemical solution and the quality of the improved body. In other words, it is very important to prevent the decrease of the permeability of the ground in the chemical injection method. Therefore, in this research, a new chemical grouting method that prevents the decrease of the permeability of the ground is developed by applying ultrasonic vibration when grouting the chemical solution. Consequently, in our previous laboratory and the field verification, it was found that the decrease of the permeability of the ground can be prevented, also the diameter and the quality of the improved body were improved by applying ultrasonic vibration when grouting the chemical solution.
A series of studies aims to develop superabsorbent polymer-based soil conditioner as new soil conditioner in classification sorting treatment of higher water content soil and viscosity soil. In this study, the soil improvement effect by the soil improvement material based on super absorbent polymer, the property of the improved soil was verified. As a result, the following contents were revealed. (1) Improvement effect by superabsorbent polymer-based soil improving material is remarkable for any target soil, and in case of homogeneous soil, improving effect can be expected more in high water content condition. Superabsorbent polymer-based soil conditioner is an improvement based only on moisture absorption of interstitial water. (2) The improved soil changes in dry density and void ratio compared with the soil before improvement, but it can be used for filling if properly managed. (3) Expansion due to water absorption of the improved soil is considered to be minor in the use of the embankment.
It is difficult to wash the contaminated fine-grained soil because the contaminants are absorbed strongly into the soil particle surface. In order to remove the contaminants which are absorbed the fine-grained soil, the washing method which is applied the function of freeze-thaw and ion exchange was proposed. In this method, the washing solution is flowed the soil particle surface by the soil freezing, the washing solution which contains ion exchange substance removes the contaminants from the soil surface and the contaminants are drained at the time of the soil thawing. In this study, the natural potassium was used as the contaminants and the ammonium acetate solution was used as the washing solution. The purpose of this study is to clarify the effective removal condition for the natural potassium ions contained sample soil. In this paper, it was investigated that the influence of the concentration of the ammonium acetate solution, times of supplying ammonium acetate solution and freeze-thaw cycles. The test result revealed the following. (1) Both washing solution intake and contaminants drainage reduced in the case of the high concentration of the ammonium acetate while the content of potassium in the drainage increased. (2) Reduction of numbers of supplying ammonium acetate solution and increment of numbers of supplying water increased both washing solution intake and drainage then that drained the contaminants effectively.
Crushed stone dust is stone powder generated in the production process of crushed stone, and crushed stone dust prepared to a maximum particle size of 2.5 mm or less is specified as "Screenings (F-2.5)" by JIS A 5001 (Crushed Stone for Road Construction). "Screenings" is mainly used as a fine aggregate of asphalt concrete for paving. Since "Screenings (F-2.5)" is a product of the stone crushing factory, the quality is relatively stable, and the fine particle fraction (75 µm or less) is also contained at about 0 to 20%, and therefore, the applicability as soil material is considered to be high. In the preliminary study, we investigated the applicability of "Screenings (F-2.5)" as base material for the surface impermeable soil liner material (soil-bentonite mixture and cement stabilized soil), and we got a suggestion that the target water permeability could be achieved by appropriately setting the types and amounts of bentonite and cement-based materials when the target compaction degree was set to Dc 95 % or more and the target water permeability coefficient in laboratory test was set to 1×10-7 cm/s or less (1×10-9 m/s or less) . In this paper, we introduce the result of proportion test carried out for the purpose of actually applying soil-bentonite mixture and cement stabilized soil using crushed stone dust (Screenings) as a base material to surface impermeable soil liner construction work.
Recently, a large amount of solidification material such as cement is used to improve high-water-content dredged clay. However, the use of such a large amount of solidification material involves the problem of high cost and raising the pH of the ground. On the other hand, bamboo has high fertility and erodes other vegetation, which causes damage to mountain forests. Therefore, it is necessary to harvest bamboo regularly. Moreover, effective use of harvested bamboo is also required from the viewpoint of environmental protection. Currently, with the miniaturization of crushers, there are increasing cases of making bamboo into chips. According to the previous studies, the effectiveness of the improved method of mixing bamboo chips and solidification material in high-water-content dredged clay is clarified. However, it is concerned that the improvement effect using bamboo chips will be different due to the difference in the water content and physical property value of the clay. Moreover, the possibility of strength reduction due to decay of bamboo chips which is organic substance is also considered. Therefore, this study examined the strength and deformation characteristics of bamboo chips mixed solidified soil using clay with different water content and liquid limit. In addition, physical and mechanical characteristics of bamboo chips mixed solidified soil which was decayed forcibly were investigated. As a result, it was revealed that the strength of the bamboo chips mixed solidified soil depends on the liquid limit and the initial water content of the clay. Moreover, it was clear that the forcedly decayed bamboo chips mixed solidified soil had long-term durability because no decrease in compressive strength was observed.
Past research has developed a powdery silica-based admixture of inorganic waste containing a large amount of silica component such as a waste glass and a fly ash. It is effective as a solidifying material by mixing with a blast furnace slag. In addition, it can be expected to have superior characteristics as well as high strength as compared with cement-based solidifying material, and it is effective to adapt to soil improvement. In this study, in order to elucidate the solidification mechanism, energy dispersive X-ray analysis (EDS analysis), scanning electron microscope observation (SEM observation) and X-ray diffraction analysis (XRD analysis) have been conducted. In addition, in order to control the solidification time, blast furnace cement or normal Portland cement or calcium hydroxide (Ca(OH)2) is partially or completely substituted for the blast furnace slag which is the raw material of the mixed solidifying material. On the contrary, the uniaxial compression test, and the flow test are carried out to investigate the usefulness and solidification mechanism in view of practical application.
In the Tsukiji district in Amagasaki city, Hyogo prefecture, Japan, where the extremely severe liquefaction-caused residential damage happened during the 1995 south Hyogo earthquake, the groundwater level has been controlled to keep GL-3.0m as the liquefaction measure by the groundwater lowering method. In this study, various ground investigations were performed at Tukiji area in June 2017 to investigate the effect of liquefaction measure by groundwater lowering as well as the present ground properties in the area where about 20 years have passed since the implementation of the measure to lower groundwater. Additionally, the liquefaction strength of the alluvial sand layer was investigated by laboratory tests using sampling specimens. In the paper, the present ground properties obtained by ground investigations were presented. Further, a result of the verifying the effect of liquefaction measure by the groundwater lowering method was reported. In the verification, liquefaction potential was evaluated for both the ground after and before the groundwater lowering was implemented on the basis of ground investigation results obtained in 2017 and 1995.
In order to assess the susceptibility to reheat cracking of high-strength austenitic stainless steels of KA-SUS304J1HTB and KA-SUS310J1TB, we established a reheat cracking reproduction test method by using stress relaxation test. A HAZ-reproduction test piece of KA-SUS304J1HTB fractured during stress relaxation at 650°C when the strain exceeded 16.6%. On the other hand, an as-received test piece of KA-SUS310J1TB fractured during stress relaxation at 650°C when the strain was more than 10.3%. Subsequently, local reduction of area (RA) of the fractured HAZ-reproduction and as-received test pieces was measured. No appreciable local RA was observed in the vicinity of the fractured surface on both test pieces. Besides, test piece with larger grain size was found out to be fractured in shorter time, as compared to test piece with small grain size. These findings were in close accordance with the previously reported characteristics of the reheat cracking cases. We then calculated the stress relaxation processes on the basis of experimental results by using Norton's creep law. The calculation results showed that HAZ-reproduction material of KA-SUS304J1HTB would not generate reheat cracking for up to more than 100,000 hours when the initial stress was equal to or below 300 MPa. However, reheat cracking would occur on KA-SUS310J1TB after only about 40,000 hours when the initial stress was 300 MPa. Compared to KA-SUS304J1HTB, KA-SUS310J1TB was more susceptible to reheat cracking.