A so-called ‘cantilever method’ has usually been adopted for the construction of long span cable-stayed bridges. It is significant to check the aerodynamic stability of this type of bridges under construction from the initial stage of erection scheme because of their flexibility.
From this point of view, this paper deals with a simplified method of estimating fundamental natural frequencies of cable-stayed bridges under construction. The author has derived a practical estimation method through a simulation analysis. Several examples demonstrating the application of the proposed method are also presented for the various construction stages of a cable-stayed bridge with the center span of 800 meters.

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Rubble stone scour protection works for the Ahashi Kaikyo Bridge pier under fast tidal currents are studied with a seepage model experiment and an experiment of the scour resistance of seabed materials. Flow in and on a rubble mound and water surfce profile around the Akashi Kaikyo bridege pier are also measured. The rubble stone scour protection work is proved to be effective to reduce the seepage flow.

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In blasting demolition work of steel-framed structures, it is very important to reduce the level of impulsive blast noise to less than the permissible level prescribed by local authorities. In this paper we describe an experimental study on the attenuation effect of sand covering the blast point on the impulsive blast noise and the empirical equation for predicting the blast noise level.
The experiments indicated that sand reduced the magnitude of peak over-pressure of air blast, as well as changed the frequency characteristics of the blast noise such that higher frequency components were suppressed. The prediction obtained from the empirical equation was compared with the values measured in the field of actual demolition work, and proved to be good for practical purposes.

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On the construction of very closely located twin tunnels, the blasting vibration from the second tunnel may damage the lining of the first tunnel. However, vibration data related to actual damage are very few and the relation between the magnitude of the vibration and the cracking of the concrete lining has not been discussed enough.
In this study, the blasting vibration and the crack formation on the shotcrete lining of the first tunnel were carefully recorded. The closest distance between the blasting point and the shotcrete lining surface was approximately 1.0m and the maximum vibration velocity reached to 145cm/sec. Cracking on the shotcrete lining was observed when the maximum vibration velocity exceeded 70cm/sec.

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In this paper, the characteristic of the CRD method developed to control the subsidence on the surface as one technique for loose ground was shown. And, the site experiment was clarified. As for the result and the amount of the site experiments, it has been understood to be able to restrain the subsidence on the surface to about 1/2 compared with the CD method. It has been recognized that the effect of control concerning the subsidence is large succesfully. This method should be able to be applied to a shallow tunnel of the city part enough.

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To analyse the mechanism of unsteady excavation of soft rock mass, several experimental tests were carried out for various rake angles and normal penetration forces acting on the cutting edge. As the results, the cutting resistance in unsteady excavation could be expressed as a function of excavation length, normal penetration force, shear strength of rock material and rake angle. The coefficient of penetration resistance could be expressed as a quadratic function of rake angle, which increases with the increment of shear strength of rock material, and takes a minimum value at about 10 degrees of rake angle. And the excavation volume of soft rock mass could be expressed as some hyperbolic function of shear strength of rock material.

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This paper explains the development of “shield Machine” applied for the Mechanical Shield Docking (MSD) method. In this method, two shield machines start excavating either side and mechanically dock without any auxiliary work method for hardening the ground around the excavation face to prevent the ground collapse of the face top and spouting out of the pressurized water.
The shild machine applied for the MSD method has developed upon the model and practical work durability test results on the excavatability such as the cutter torque, thrust force and excavation face stability, and strength characteristics of the cutter and shield skin plate.

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Non-linear settlement behaviour of axially loaded pile under actual working load is studied in this paper based on many loading test data accumulated in our country for these 30 years. Almost all of piles designed as a bearing pile are confirmed to behave as a friction pile due to the finite axial rigidity of pile.
Non-dimensional and numerical analysis of non-linear differential equation governing the frictional behaviour are discussed and compared with test results. Constant of frictional subgrade reaction for the analysis is presented by using SPT-value N. An approximating procedure and a chart for estimating pile settlement are proposed.

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This paper desk with basic properties of cement suspension grouts with differnt grain sizes and their penetration into sand and into cracks in rock masses. The main results are as follows. (1) The penetration of the grouts into dense sands or narrow cracks increased considerably with decreasing grain size. For an ultra fine grained cement grout it was excellent. (2) Dispersion admixtures increased the penetration of grouts made of ordinary grain size cements or of fine cements with a low water cement ratio. In field grouting tests in rock, the superiority of ultra fine cement to poltland blast furnace slag cement was realized.

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This paper describes the properties of the highly flowable concrete using low heat generating cement. Firstly, influences of several admixtures on the properties of the concrete were determined. It was verified that setting time of the concrete could be controlled by adding the additives, maintaining the required qualities of the concrete. Secondly, the two mixtures were placed into the formwork. The time-dependent change in the lateral pressures and those maximum values against the formwork were measured. The actual lateral pressures were tentatively calculated using both the cohesion and the internal friction angle of the concrete.

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Accidents and disasters have been, it is regretable, brought about very often. Apart from a kind of the so-called natural calamities, it is pointed out that slight carelessness or negligence of those people concerned is responsible for the case of accidents and disasters every time such trouble occurs. However with respect to the accidents and disasters, there are problematic points not allowed to be disposed of with such attitudes. Keeping such problematic points entirely in mind, this paper observes the fundamental characteristics of the safety problems of accidents and disasters. Furthermore increase of the real safety and proper measures to rescue those suffered from the calamities are discussed.

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Statistical analyses of occupational accidents associated with construction work were carried out to explore the basic statistical characteristics of their damge consequences. Emphasis was placed upon the probabilistic and statistical analyses to clarify, in particular, the relationship between frequency of labour accidents and their damage consequences. Damage consequences were classified into two categories such as the number of workdays lost due to accidents and the number of injured workers involved in one accident. Two types of accident data were collected for the analyses. From the analyses, it was found that the relation between damage due to accidents and their frequencies can be represented by a simple power function which indicates a log-log linear relation. By making use of this relationship, various probabilistic evaluations such as the estimation of the mean time periods between accidents, expected damage consequences, and expected damage ratio between different mean time period of accidents were conducted.

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In-situ investigations were carried out to examine the performance of seismic, radar and registivity tomography techniques . Geological structures and characterisitics of the site were estimated integrating all the tomography results.
Several boreholes were drilled in the tomography sections after the geophysical measurements. The observed results of borehole cores were used to verify the results of tomography analyses.
As the result, the followings were concluded. (1) Seismic tomography by primary wave velocity is effective to classify rock mass quality. (2) The stratum structure is clearly expressed using the tomography of rader wave velocity. (3) It is important to integrate all the tomography results for the estimation of geological characteristics such as mechanical properties and fracture distribution.

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Stability analysis methods for a “isolated ground” surrounded by a diaphragm wall were studied based on the collapse which occurred at the site and it is confirmed that a “3 dimentional cylindrical sliding theory” is practical for the analysis. A excess pore water pressure developed in the isolated ground was higher than that of the outside of the diaphragm wall and it was found that a “surge pipe” with slits effectively reduced the excess pore water pressure.

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A relative position detecting system of two shield tunneling machines has been developed for the underground docking. Using a horizontal boring machine and two types of position sensors, the system provides nondestructive and very precise confirmation of the relative postion of two shield machines without conducting a conventional check boring from ground surface.
The paper describes the development of the system and the results of its application to an actual project.

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