A formula to predict unconfined compression strength of cement-treated marine clays is proposed. The formula has a form similar to the gel-space ratio theory of hardened cement paste. In the proposed formula, the strength of cement-treated soil is given by volumetric solid content, strength increase coefficient due to cement, exponential parameter N representing the effect of void structure of soil and cement content to all the solid material of soil. The formula is adapted to the results of laboratory strength tests of cement-treated soils made of 6 dredged marine clays. The strengths estimated by the proposed equation agreed with the measured strengths fairly well, using the parameter N=3.5-4.5. The formula is applicable to the strength estimate of foam treated soil and beads treated soil which was made from the dredged marine clay, using the parameter N=2.1-2.5.

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Improved anti-corrosion anchors have been used since ground anchor (hereinafter anchors) standards were revised in 1978 by the Japanese Committee of Soil Mechanics and Foundation Engineering (current Japanese Geotechnical Society). But tension members used for anchors constructed before the revision are vulnerable to corrosion. It is, therefore, necessary to place priority on maintenance of these anchors. A large portion of the anchor is embedded underground, and it is difficult to directly confirm corrosion and deformation of the tension member. In this study we have conducted lift-off tests on and dug up anchors that are around 35 years old to investigate the situation, and proposed points to keep in mind when evaluating the soundness of corroded anchors.

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In repairing project of the old earth dam, the standard penetration test (SPT) is carried out to investigate a geotechnical condition of the embankment at the design process. However, mostly there is not enough geotechnical investigation by SPT to investigate the embankment condition in detail comparing with the new project of the earth dam.
This paper represents the applicability of small dynamic penetration test (Mini-Ram Sounding, mRS) as a complementary investigation of SPT to investigate the old earth dam embankment. The system of mRS is a small, light-weight, and cost-effective site investigation technique to provide the geotechnical information obtaining a strong correlation with the results of SPT. It was confirmed that there are a good relationship between N_mRS values obtained from mRS and N_SPT values from SPT.

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In Japan, although the recycling of waste has been promoted, there may be various obstacles. In this study, we focus on construction waste, more specifically, construction sludge, which is less advanced in terms of recycling. Processing cost for materials recycled from construction sludge is higher compared to the cost of mining virgin materials. There are some additional difficulties including delays in schedules due to the time required for processing and the balance between supply and demand. Therefore, we quantitatively assess the benefit of recycling by adding the time factor to the evaluation model with consideration for cost and environmental load. As a result, it is shown that the bottlenecks of construction sludge recycling are higher cost than the cost of mining of virgin materials, high heavy metal contents in the construction sludge, and delays in the recycling process.

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For the purpose of improving new grout composed of calcium phosphate compound (CPC-Chem), the authors have conducted the unconfined compression test and scanning electron microscopy (SEM) observation on Toyoura sands cemented with CPC-Chem and 4 kinds of powder (tricalcium phosphate, TCP; magnesium phosphate, MgP; calcium carbonate, CC; magnesium carbonate, MgC). In comparison with the unconfined compressive strength (UCS) of CPC-Chem cemented sand, the UCS of the CPC-Chem cemented sand with TCP or CC powder significantly increases and exceeds the target strength of 100 kPa, reaching a maximum strength of 261.4 kPa and 209.7 kPa, respectively. The precipitates in the cemented sand with CPC-Chem and the addition of 1% or 5% TCP, or with 1% CC have net-like and three-dimensional structures. These results suggest the feasibility of CPC-Chem with TCP or CC powder as a non-contaminating and recyclable biogrout using microbial activity while providing sufficient strength required for ground improvement.

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