162A
IN SITU STRESS:MEASUREMENT
region of the North East of England. Generally the superficial
deposits consist of glacial materials. These data are being
assessed to allow a model to be developed of the geological
and geotechnical processes that have taken place. In this
paper the results of a simple statistical study of the
classification and strength data are presented. (Authors)
954096
Geoteehnicai characterization of blended coal tailings for
construction and rehabilitation work
B. Indraratna, Quarterly Journal of Engineering Geology,
27(4), 1994, pp 353-361.
Coarse and fine refuse is produced by various coal processing
equipment. The relatively wet fine railings have limited use in
construction activities and they are generally pumped as
slurries into tailings ponds. The coarse rejects have a greater
engineering applicability and are utilized in the construction
of railings dams and mine access roads as well as for landfill
and ballast. This study investigates the fundamental engineering properties of blended tailings, whereby appropriate
fractions of flotation tailings are mixed with cyclone rejects to
produce an acceptable construction or rehabilitation fill. In
particular, a practical procedure to optimize the blended
ratios, is proposed on the basis of fundamental geotechnical
testing. The applications of relevent tests are described,
including Proctor compaction, California Bearing Ratios,
triaxial and consolidation tests. The results confirm that
blending of fines with coarse rejects enables enhanced dry
densities associated with reduced permcabilities, higher shear
and compressive strengths, lower consolidation settlements
and increased bearing capacities. The addition of a small
quantity of cement (2-5%) further improves the engineering
properties of the blended matrix. (from Author)
IN S I T U STRESS
Causes and nature of in situ stress
954097
Numerical simulation of roadway maintenance by stress
control method (in Chinese)
Ju Wenjun, Journal - China Coal Society, 19(6), 1994, pp
573-580.
Based on a complete stress-strain curve of the rock, an
elastoplastie formula describing rock deformation failure is
established. An FEM program is used to investigate the
mechanism for maintaining roadways by stress control. The
layout of weakened zone and the effect of parameters relevant
to weakened zone on roadway maintenance is also studied.
The results show that after local weakening of the rock, the
stress concentration area in the roadway moves to the depths
of the surrounding rock, and the stability of rock is greatly
improved. The layout of weakened zone and its parameters
will be determined by rock conditions of the roadway and
stress environment. (English summary)
Measurement of in situ stress
954098
Monitoring stress changes in three dimensions using a solid
cylindrical cell
A.-P. Bois, G. Ballivy & K. Saleh, International Journal of
Rock Mechanics & Mining Sciences, 31(6), 1994, pp 707-718.
Presents a mathematical analysis of an inclusion device to
carry out long-term strain-stress variation monitoring. The
device consists of a solid cylinder grouted into a borehole.
Analysis of the influence of the Young's moduli of the sealing
grout and of the surrounding material revealed that a thin
layer of grout should be used to seal the cylinder and that
rigid cells should not be considered for monitoring strainstress variations in three dimensions. (from Authors)
954099
Stresses around a circular opening in an elastoplastic
porous medium subjected to repeated hydraulic loading
Y. Wang & M. B. Dusseault, International Journal of Rock
Mechanics & Mining Sciences, 31(6), 1994, pp 597-616.
Stresses near a circular borehole under repeated interior
loading are analyzed. In a porous material which is capable of
plastic deformation, the stresses and strains adjacent ot a
borehole depend on the loading history. Varying loadings
inside a circular opening are imposed to simulate the nonmonotonic pressure changes that arise during drilling and
injection in a borehole. Plastic yielding related to different
yielding modes is explored. Stages in the development of such
stress states are analyzed, and the stress states in different
zones under various circumstances are calculated separately
and summed. The solutions presented can be used to
understand stress development around boreholes, and can
also be used to interpret hollow cylinder test results. (from
Authors)
954100
Back analysis of stress measurement of anisotropic rock
mass (in Chinese)
C a t Wengui & Y a n Ronggui, Journal of China Coal Society,
19(2), 1994, pp 122-130.
As soon as distribution of 3D stress and strain around a
homogeneous borehole is established, 3D stress measurement
by using a single borehole becomes successful in in-situ stress
measurement in homogenous rock mass. Due to the difficulty
in establishment of stress and strain distribution around a
borehole anisotropic rock mass by mathematic methods, the
authors introduced a back analysis method, and found a
solution by means of 3D FEM. It was verified by an example.
(from English summary)
954101
Back analysis of initial stresses in rock masses (in Chinese)
Zhu Bofang, Shuili Xuebao/Journal of Hydraulic Engineering, 10, 1994, pp 30-35.
Two methods are given for the back analysis of the initial
stresses in rock masses. By using the first method, the initial
stresses in rock masses in a small area are determined from
the displacements observed during the process of tunnelling.
By using the second method, the initial stress field in the rock
masses in a large area are determined from the observed in
situ stresses. The number of variables of regression is reduced
and the accuracy of computation is improved due to the use
of these methods. (English summary)
954102
Confidence intervals for in situ stress measurements
A. J. Jupe, International Journal of Rock Mechanics &
Mining Sciences, 31(6), 1994, pp 743-747.
Walker et aL proposed a method of evaluating confidence
intervals for in situ stress measurements which employed the
Monte-Carlo sampling of the normal probability distribution
function estimated from a number of independent overcoring
measurements taken within one borehole. This note discusses
an alternative means of evaluating confidence intervals from
overcoring data and compares the technique with that of
Walker et al.. As with their method, the technique makes use
of random sampling to simulate a repetition of the overcoring
experiment. However, rather than using the Monte-Carlo
approach, it makes use of the statistical technique known as
Jacknifing. (from Author)
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