英语学术论文

题目：用解析的方法估算围岩的自稳时间。

1.What is stand-up time？

Stand-up time is defined as the amount of time a tunnel will support itself without any added support structures, which means also the time that the rock mass around the tunnel begin to collapse(倒塌).

公式：

Here is what the stand-up time means.

There are some major factors.

t f is the stand-up time in years; Mrj is combined the influence of compressive strength （抗压强度）(rcj) of rock mass and tangent modulus （切线模量） (Etj) of rock mass（divide 除）:Su is the effective span （有效跨度） in meters; po is the in-situ stress （原地应力）in t/m2 and usp is the seepage pressure（渗透压力） in t/m2. ks is the constant（常量） linked to Mrj

Fig2

Let’s see what’s the active span L means

Here is the tunnel face and this is the length of the excavation part. And this shows the L is shorter than the B and this shows the L is longer than the B. And what does this means? OK the next fig will tell us. Fig1

The X-axis means the stand-up time and the Y-axis means the Active span L. And we can see in this fig. With the increasing length of the active span the stand-up time decreased. And the letter A B C D means different kinds of rock mass. And we will explain them later.

2.Rock mass classification methods(围岩分级方法)

Fig 3

OK the first one is the Q-system. The X-axis means the stand-up time and the Y-axis means the unsupported span(无支护跨度)。And we can see five different kinds of rock here. And the Q is bigger and the Stand-up time is longger.

Fig4

OK the second one is RMR-system. The X-axis means the stand-up time and the Y-axis means the roof span(顶板跨度)。 We can see in this fig that the RMR-system’s results are just like the Q-system’s results. They are in the same shape and same magnitude(量级)。

3.Rock mass model(建立模型)

Fig5

Here is the mechanical model(力学模型) for tunnel excavation（隧道开挖）. Here is the ground surface. And the depth of the tunnel is H. And the tunnel is in a homogeneous(均匀的) isotropic（各向同性的） rock mass. The tunnel is subjected to （受到）a uniform hydrostatic stress field(静水压力)(@。) And internal（内压力） pressure(Po) uniformly （一致的）acts on the tunnel wall surface.

Fig6

OK，let’s see how the depth influences the stand-up time of the tunnel. The X-axis means the stand-up time and the Y-axis means the unsupported span(无支护跨度)。Here are five different tunnel depths. The results indicate that the impact of(影响) the tunnel depth on the stand-up time of tunnel. The stand-up time decreases with increasing the tunnel depth. Therefore, the stand-up time for the deeper tunnel is shorter than that of shallow(埋深浅的) tunnel.

Table5

The table shows the rock mass properties. The siltstones(砂泥岩) are in there different Young’s modulus（杨氏模量）. They are 6.2,14.0 and 23.5 GPa, that means poor, fair and good rock mass.

Fig7

And the fig shows how the Young’s modulus influences the stand-up time of the tunnel. The result indicates that the stand-up time is greater in the good rock mass quality in comparison with fair and poor rock mass qualities.

4.Result

Estimation(估计) of stand-up time of the rock mass is to have great meaningful in the selection of excavation methods as well as methods for rock reinforcement（围岩加固） in the most effective way possible. Question

How many Rock mass classification methods have been involved in this paper? What are they?

Two. The Q-system and the RMR-system.

How does the the depth influence the stand-up time of the tunnel?

The stand-up time decreases with increasing the tunnel depth. Therefore, the stand-up time for the deeper tunnel is shorter than that of shallow(埋

深浅的) tunnel.