671017.pdf

e force of

gravity

e propagation of

aphanitic microcracks

e slip of original joints

Relaxation of aphanitic

Rotation of original

joints

microcracks

(a) (b)

(d) (c)

Figure 1: Failure modes of surrounding rock in the cavity.

extending and splitting of aphanitic microcracks. In addition,
the surrounding rock on the cavern side wall generated a large
amount of broken rocks, especially in the region where the
cracking failures of original joints are concentrated, which is
seen in the failure model shown in Figures 1 (c) and 1 (d). Since
the aphanitic microcracks are randomly developed inside the
columns and it is impossible to count their number, it is
more appropriate to adopt equivalent method for analysis and
research in light of the research results of the literature [ 7 – 11 ].

3. D-CRDM (Discrete Element Method-Crack

Rock Mass Deterioration Model)

D-CRDM analysis method simulates original joints by 3DEC
block theory and develops constitutive deterioration model
of jointed rock by using its secondary development function
in order to implement coupling analysis of these two kinds of
joints.
After excavation, the aphanitic microcracks on the sur-
face of surrounding rocks gradually extend and crack under

the effect of unloading, resulting in the deterioration of

overallmechanicalpropertiesofcolumnarjointedbasalt.

From a macro perspective, this type of deterioration can

be considered as a changing process of Young’s modulus퐸,

Poisson’s ratio휇,cohesion퐶,frictionangle휙,tensilestrength

푇, and other mechanical parameters of the rock mass. There-

fore, when adopting numerical simulation method to study

the mechanical behaviour of columnar jointed basalt, its

constitutive model should accurately reflect two fundamental

features of the rock mass; that is, the mechanics parameters

change along with the damage of surrounding rock both

during and after the yielding course of rock mass. In rock

deterioration process, each parameter change should be

determined by the mechanical state of rock mass, while the

mechanical index of equivalent plastic strain휀푝is usually

used to describe different stress state of rock mass, which is

defined

휀푝=∫√

2

3

(휀 1 푝휀푝 1 +휀 2 푝휀푝 2 +휀푝 3 휀푝 3 ). (1)