问题 问答题 案例分析题

背景资料

某城市跨线桥工程,上部结构为现浇预应力混凝土连续梁,其中主跨跨径为30m并跨越一条宽20m河道;桥梁基础采用直径1.5m的钻孔桩,承台尺寸为12.Om×7.Om×2.5m(长×宽×高),承台顶标高为+7.Om,承台边缘距驳岸最近距离为1.5m;河道常水位为怕+8.0m,河床底标高为+5.Om,河道管理部门要求通航宽度不得小于12m。工程地质资料反映:地面以下2m为素填土,素填土以下为粉砂土,原地面标高为+10.Om。项目部进场后编制了施工组织设计,并对钻孔桩、大体积混凝土、承重支架模板、预应力张拉等关键分项工程编制了安全专项施工方案。项目部的安全负责人组织项目部施工管理人员进行安全技术交底后开始施工。第一根钻孔桩成孔后进入后续工序施工,二次清孔合格后,项目部通知商品混凝土厂家供应混凝土并准备水下混凝土灌注工作。首批混凝土灌注时发生堵管现象,项目部立即按要求进行了处理。现浇诫应力混凝土连续梁在跨越河道段采用门洞支架,对通行孔设置了安全设施;在河岸两侧采用满布式支架,对支架基础按设计要求进行处理,并明确在浇筑混凝土时需型排专人值守的保护措施。上部结构施工时,项目部采取如下方法安装钢绞线:纵向长束在混凝土浇筑之前穿入管道;两端张拉的横向束在混凝土浇筑之后穿入管道。

问题

1.结合背景资料和《建设工程安全生产管理条例》,补齐安全专项施工方案。

2.说明项目部安全技术交底的正确做法。

3.分析堵管发生的可能原因,给出在确保桩质量的条件下合适的处理措施。

4.现浇预应力混凝土连续梁的支架还应满足哪些技术要求?

5.浇筑混凝土时还应对支架采取什么保护措施?

6.补充项目部采用的钢绞线安装方法中的其余要求。

答案

参考答案:

1.(本小题3分)

结合背景资料和《建设工程安全生产管理条例》,需编制安全专项施工方案的工程包括:基坑支护(1分)和降水工程(1分)、土石方开挖工程(1分)。

2.(本小题4分)

项目部安全技术交底的正确做法:工程施工前,施工单位负责项目管理的技术人员应当对有关安全施工的技术要求向所有作业班组、作业人员进行书面交底(3分),履行签字手续并形成记录归档(1分)。

3.(本小题6分)

堵管发生的可能原因:灌注导管破漏、灌注导管底距孔底深度太小、完成二次清孔后灌注混凝土的准备时间太长、隔水栓不规范、混凝土配制质量差、灌注过程中灌注导管埋深太大(2分)。

在确保桩质量的条件下合适的处理措施:可用长杆冲捣管内混凝土,用吊绳抖动导管,或在导管上安装附着式振捣器等使隔水栓下落。如仍不能下落时,则须将导管连同其内的混凝土提出钻孔,进行清理修整(注意切勿使导管内的混凝土落人井孔),然后重新吊装导管,重新灌注。一旦有混凝土拌合物落入井孔,须将散落在孔底的拌合物粒料等予以清除(2分)。当灌注时间已久,孔内首批混凝土已初凝,导管内又堵塞有混凝土,此时应将导管拔出,重新安设钻机,利用较小钻头将钢筋笼以内的混凝土钻挖吸出,用冲抓锥将钢筋骨架逐一拔出。然后以黏土掺砂砾填塞井孔,待沉实后重新钻孔成桩(2分)。

4.(本小题3分)

现浇预应力混凝土连续梁的支架还应满足的技术要求:(1)支架应稳定,强度、刚度应符合规范要求(1分)。支架的立柱应保持稳定,并用撑杆固定。验算倾覆的稳定系数不得小于l.3。受载后挠曲的杆件(盖梁、纵梁)的弹性挠度不得大于相应结构跨度的l/400(1分)。(2)支架的弹性、非弹性变形及基础的允许下沉量应满足施工后梁体设计标高的要求(1分)。

5.(本小题4分)

浇筑混凝土时,应能够抵抗施工过程中可能发生的偶然冲撞和振动:(1)支架立柱必须安装在足够承载力的地基上,立柱底端应设垫木来分散和传递压力,并保证浇筑混凝土后不发生超过允许量的沉降量(2分)。(2)船只或汽车通行孔的两边支架应加设护桩,夜间应用灯光标明行驶方向。施工中易受漂浮物撞击的河中支架应设坚固的防护设备(2分)。

6.(本小题10分)

项目部采用的钢绞线安装方法中的其余要求:

(1)先穿束后浇混凝土时,浇筑混凝土之前,必须检查管道确认完好;浇筑混凝土时应定时抽动、转动预应力筋(2分)。

(2)先浇混凝土后穿束时,浇筑后应立即疏通管道,确保其畅通(2分)。

(3)混凝土采用蒸汽养护时,养护期内不得装入预应力筋(2分)。

(4)穿束后至孔道灌浆完成,应控制在下列时间以内,否则应对预应力筋采取防锈措施:①空气湿度大于70%或盐分过大时,7d;②空气湿度40%~70%时,15d;③空气湿度小于40%时,20d(2分)。

(5)在预应力筋附近进行电焊时,应对预应力钢筋采取保护措施(2分)。

选择题
阅读理解

Mainland couples who give birth to a second child in Hong Kong will be fined for breaking the family planning policy,a senior official has warned.

As more women flock to Hong Kong to give birth to their second child,Zhang Feng,family planning department director of Guangdong Province,stressed that this violated China's policies.

“And those who are government employees will even be dismissed from their posts.”he said.

“It doesn’t matter if they give birth to their second child on the mainland or in other countries and regions , they have violated the country’s policies and the probince’s regulations”.

He said that some families had been punished in the past few months after having a second in Hong Kong , but gave no details .

Zhang made his remarks when a Hong Kong newspaper carried a controversial notice claiming residents’ medical services had been affected by the growing number of mainland women who arrive in the city to give birth and gain fight of abode (居住)there.

According to statistics revealed by Hong Kong Special Administrative Region government,about 88,000 babies were born in Hong Kong in 2010,but more than 41,000 or 47 percent,were to mainland couples,including a large number from Guangdong.

Hong Kong has limited the number of mainland women permitted to give birth in the city at 34,000 this year.

The issue also has caused calls for an amendment(修正)to Hong Kong's Basic Law so that babies born to mainland women are no longer granted permanent fight of abode.

“I support Hong Kong government's decision to reduce or limit the number for mainland women giving birth in Hong Kong.”Zhang said.

China introduced its family planning policy in 1979 to limit births in the world's most populous nation,although the rules have been relaxed in recent years.

小题1:Which of the following is true?

A.Those who give birth to a second child in Hong Kong will be fined.

B.Many government employees have been dismissed from their posts.

C.Zhang Feng is family planning department director of Guangdong Province.

D.It doesn't matter if they give birth to their second child on the mainland.小题2:What does the word “violated” mean in the second paragraph?

A.went against

B.was obeyed

C.was for

D.was dismissed小题3:Zhang Feng said that          .

A.few families had been punished after having a second child in China

B.about 88,000 babies were born in Hong Kong in 2010

C.the residents' medical services in Hong Kong had been affected

D.he agreed to reduce or limit the number for mainland women giving birth in Hong Kong小题4:From the passage we can infer       .

A.in 2010 most of the babies born in Hong Kong belonged to mainland couples

B.the number of mainland women permitted to give birth in Hong Kong has been reduced

C.babies born to mainland women in Hong Kong can't get permanent right of abode now

D.the family planning policy in China is as strict as before小题5:Which is NOT the reason why some people want to give birth to a second child in Hong Kong?

A.They want to gain right of abode(居住)there for their babies.

B.They want to escape being punished for breaking the family planning policy.

C.They want to cause calls for an amendment(修正)to Hong Kong's Basic Law.

D.They want their babies to enjoy the good medical services in Hong Kong.