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1、 承台大体积砼施工前的温度应力估算及采取的裂缝控制技术措施摘要：介绍重庆白果渡嘉陵江大桥主桥承台大体积砼施工前温度应力的估算，并根据验算结果采取相应的施工技术措施。 关键词：大体积砼 承台 裂缝控制 温度应力 施工技术措施 1 引言 白果渡嘉陵江大桥是国道212线四川武胜至重庆合川高速公路横跨嘉陵江的一座特大桥，全桥长1433米，主桥为（130+230+130）m预应力砼连续刚构，单箱单室，下部结构为16根24米长230cm的群桩基础，上接大体积分离式承台。单幅承台结构尺寸为18.7mx10.2mx5m，单幅承台砼方量为953.7m3，一次浇注完成。2 简述2.1&nbs
2、p;温度应力的主要成因：2.1.1 大体积砼在硬化期间，水泥水化后释放大量的热量，使砼中心区域温度升高，而砼表面和边界由于受气温影响温度较低，从而在断面上形成较大的温差，使砼的内部产生压应力，表面产生拉应力（称为内部约束应力）。 2.1.2 当砼的水化热发展到37d达到温度最高点，由于散热逐渐产生降温产生收缩，且由于水分的散失，使收缩加剧，这种收缩在受到基岩等约束后产生拉应力（称为外部约束应力）。2.2 温度应力在承台砼内的分布如下图所示： 综上所述，在承台大体积砼施工前，必须进行砼的温度变化，应力变化的估算，以确定养护措施、分层厚度、浇筑温度等施工措施，并以此
3、来指导施工。 3 C30承台大体积砼砼裂缝控制的施工计算3.1相关资料：3.1.1 配合比 水泥：粉煤灰：砂子：碎石：水：NNO -减水剂 369： 50 ：677 ：1148：176：3.66 1： 0.136：1.835：3.111：0.48：1%3.1.2 材料：水泥：腾辉F.032.5级水泥碎石：草街连续级配碎石（531.5mm）混合中砂：机制砂40%，渠河细砂60%粉煤灰：硌黄华能电厂级粉煤灰外加剂：达华NNO-型缓凝减水剂3.1.3 气象资料相对湿度8082%；年平均气温17.517.6，最高气温40.5，夏热期（59月份）平均
4、气温20。 3.1.4采用自动配料机送料，装载机加料，拌和站集中拌和，混凝土泵输送砼至模内。3.2 砼最高水化热温度及3d 、7d的水化热绝热温度C=369kg/m3；粉煤灰32.5水泥：水化热Q7d=257J/kg，Q28d=222J/kg（腾辉水泥厂提供的数据）；c=0.96 J/kg.k；=2400 kg/m3。3.2.1 砼最高水化热绝热温升Tmax=CQ/c=(366*257)/(0.96*2400)=40.833.2.2 3d的绝热温升T（3）=40.83*(1-e-0.3*3)=24.23T（3）=24.23-0=24.23 3.2.3 7
5、d的绝热温升 T（7）=40.83*(1-e-0.3*7)=35.83 T（7）=35.83-24.23=11.6 (4)15d的绝热温升 T（15）=40.83*(1-e-0.3*15)=40.38T（15）=40.38-35.83=4.55 3.3 砼各龄期收缩变形值计算y（t）=y0（1-e-0.01t）*M1*M2*M10查表得：M1=1.10，M2=1.0，M3=1.0，M4=1.21，M5=1.2，M6=1.11(1d)、1.09(3d)、1.0(
6、7d)、0.93(15d) ， M7=0.7， M8=1.4，M9=1.0，M10=0.895则有：M1M2M3M4M5M7M8M9M10 =1.10*1.0*1.0*1.21*1.2*0.7*1.4*1.0*0.895=1.4013.3.1 3d收缩变形值 y（3）=y0*（1-e-0.03）*1.401*M6 =3.24*10-4*（1-e-0.03）*1.401*1.09=0.146*10-43.3.2 7d收缩变形
7、值 y（7）=y0*（1-e-0.07）*1.401*M6 =3.24*10-4*（1-e-0.07）*1.401*1.0=0.307*101-43.3.3 15d收缩变形值 y（15）=y0*（1-e-0.15）*1.401*M6 =3.24*10-4*（1-e-0.15）*1.401*0.93=0.588*10-43.4 砼收缩变形换算成当量温差3.4.1 3dT（y）（
8、3）=-y（3）/=(-0.146*10-4)/(1.0*10-5)=-1.463.4.2 7dT（y）（7）=-y（7）/=(-0.307*10-4)/(1.0*10-5)=-3.073.4.3 15dT（y）（15）=-y（15）/=(-0.588*10-4)/(1.0*10-5)=-5.88 3.5 各龄期砼模量计算E（t）=Ec*（1-e-0.09t）3.5.1 3d龄期 E（3）=3.0*104*（1-e-0.09*3） &nb
9、sp; =7.1*103N/mm23.5.2 7d龄期 E（7）=3.0*104*（1-e-0.09*7） =1.40*104N/mm23.5.3 15d龄期 E（15）=3.0*104*（1-e-0.09*15） =2.22*104N/mm23.6 砼的温度收缩应力计算砼强度换算f（n）=f（28）*lgn/lg28，砼抗
10、拉强度ft=0.23*f2/3cu 对于C30砼f（28）=15 N/mm23d龄期: f（3）=f（28）*lg3/lg28=15* lg3/lg28=8.76 N/mm2ft=0.23f2/3(3)=0.23*4.952/3=0.668 N/mm27d龄期: f（7）=f（28）*lg7/lg28=15* lg7/lg28=8.76 N/mm2ft=0.23f2/3(7)=0.23*8.762/3=0.98 N/mm2由于在七月份浇注承台砼，气温较高，假设入模温度To=30，Th=25 3.6.1 3d龄期
11、 H（t）=0.57,R=0.35,V=0.15 T= To+2/3T(t)+Ty(t)-Th=30+2/3*24.23+1.46-25=22.61 =-(7.1*103*10*10-6*22.61*0.57*0.35)/(1-0.15) =0.377 N/mm2(0.668/1.15)=0.581 N/mm2 可3.6.2 7d龄期 H（t）=0
12、.502,R=0.35,V=0.15 T= 30+2/3*35.83+3.07-25=31.96 =-(1.4*104*10*10-6*31.96*0.502*0.35)/(1-0.15) =0.93 N/mm20.98N/mm2 抗裂安全系数：K=0.98/0.93=1.05<1.15 4 裂缝控制的施工技术措施通过以上分析可知，承台基础在露天养护期间，7d龄期时，抗裂安全系数K值稍小于1.15，此时砼有可能出现裂缝，因此，在设计配合比、砼施工
13、过程及养护期间应采取一定措施，以减小砼表面与内部温差值，使得砼表面与砼内部温差小于25，/（1.15）ft，则可控制裂缝的不出现。采取如下措施：4.1 采用双掺技术，掺入粉煤灰和NNO-II型缓凝减水剂，粉煤灰掺入采用超量代换法，减水剂的缓凝时间15个小时（通过实验室测定结果表明），延缓砼的初凝时间，延缓砼水化热峰值的出现。4.2 通过技术性能比较，石灰岩碎石的线膨胀系数较小，弹模低，极限拉伸值大，据相关资料表明，在相同温差下，温度应力可减小50%，能提高砼的抗拉强度，因此，选用石灰岩碎石作为粗骨料；控制骨料（砂、石）的含泥量，以减小砼的收缩，提高极限拉伸。4.3
14、;严格控制砼的入模温度在30左右。选择在傍晚开始浇注承台砼，对粗骨料进行喷水和护盖；施工现场设置遮阳设施，搭设彩条布棚，避免阳光直晒；在水箱中加入冰块，降低拌和水的温度；在基坑内设一大功率的鼓风机进行通风散热。4.4 埋设6层冷却管，每层冷却管配一潜水泵，在第一批开始砼初凝时由专人负责往冷却管内注入凉水降温，冷却水流速应大于15L/min，冷却水采用嘉陵江水，持续养生7天。通过冷却排水，带走砼体内的热量，许多工程实践表明，此方法可使大体积砼体内的温度降低34摄氏度。4.5 浇注砼时，采用薄层浇注，控制砼在浇注过程中均匀上升，避免砼拌和物堆积过大高差，砼的分层厚度控制在203
15、0cm。4.6 设10台插入式振捣器，加强振捣，以期获得密实的砼，提高密实度和抗拉强度，浇注后，及时排除表面积水，进行二次抹面，防止早期收缩裂缝的出现。4.7 砼浇注后，搭设遮阳布棚，避免阳光曝晒承台表面。4.8 砼浇注后，砼表面用土工布覆盖保温，并洒水养生，使砼缓慢降温、缓慢干燥，减少砼内外温差。4.9 砼浇筑后，每2小时量测冷却管出口的水温和砼表面温度，若温差大于20时，及时调整养护措施，如加快冷却水的流通速度等措施，以控制温差小于25。5 温度监测承台砼入模温度为3034，1.5d后中心温度最高达50，温升达20，3d后中心温度达576
16、0，温升2730，经过1012d降温阶段后，中心温度基本稳定。承台中心与侧面中心温度的最大温差为10，与承台表面的最大温差为17左右，因此，在养护阶段必须做好承台表面的保温措施，延缓承台表面的降温速度，减小温差。6 结束语通过事先裂缝控制的验算及裂缝控制方案的周密考虑，成功地控制了承台裂缝的产生，施工后检查承台砼各表面整体光滑，未见收缩裂缝。从本工程的裂缝控制得出：裂缝控制应以合理的结构设计为基础，具体施工中从合理选材入手，加以事先裂缝控制验算并采取适当的控制措施，全方位、多层次地进行裂缝控制，才能做到真正意义上的裂缝控制。/Porganization system and working m
17、ode, the selection of a number of municipal strengthening group to build innovation and strengthen the organization of the basic level organizations advanced model.(seven) the manual work of the Communist Youth League Organization published and League branch of manual work, to promote the use of two
18、 manuals in the citys organizations at various levels. The county committee, directly under the group (work) is under the jurisdiction of grassroots League and group (total) using branch ratio shall not be less than 70%.Three, to further strengthen the groups leadership and team building(a) to stren
19、gthen the leagues leadership at all levels of construction. Continue to do a good job of municipal Party Committee Organization Department on the strengthening of the Communist Youth League cadres management opinions implementation. To promote the group counties (autonomous counties, cities) Commiss
20、ion and city directly under the group (workers) appointed to carry out the Five team building activities. Improve the League Association Department working mechanism. Conscientiously fulfill the duties of CO, combined with the city group directly under (the) Committee of the general election and the
21、 adjustment, actively jointly with the unit where the party organization department good group leadership selection with the work. Do a good job in municipal Party committee assistant committee leadership and leading cadres of the annual assessment work, adhere to and improve the assistant secretary
22、 of the Communist Youth League talk system group To weave individual conversation and collective conversation, to strengthen the committees of all levels, the Standing Committee of the Standing Committee, the establishment of a sound system of central group learning, the system of investigation and
23、study, the system of important issues and the reporting system.(two) to strengthen the work of education and training of cadres to conscientiously implement the Central Committee. On the implementation of grassroots cadres training project and opinions on carrying out the mission municipal CYL Cadre
24、s training project implementation opinions, full implementation of the project of the City Youth League cadres training education. Focus on the county grassroots cadres and workers focused on training, the new school system vocational training League cadres, for the Municipal Organization Department
25、 jointly held the third session of the Communist Youth League system training cadres in party. Focusing on the construction of new socialist countryside, strengthening village cadres and rural construction team group member of the young team, the county organizations at various levels throughout the
26、 year is expected to train 100 00 rural grassroots cadres, plans to train 1000 village secretary of the village Party branch.(three) actively promote grassroots cadres election work. Under the unified leadership of the party organization, to strengthen grassroots organizations direct work, standardi
27、ze the election work rules and procedures, in the designated candidate, open competition to democratically elected branch secretary at the same time, actively and steadily the development of Township, streets and other grassroots organizations in the direct election of the pilot work, on the basis o
28、f summarizing the experience and gradually expand the scope of the pilot, and gradually formed a set of measures and cadres election system.(four) to strengthen the cadres testing exercise. To study the development of XX city from 2006 to 2008 cadres testing exercise planning. To select outstanding
29、cadres to the central mission in Beijing, Shanghai, Guangzhou and other central organs and sending work in developed areas. With the Central Committee the implementation of the western region and ethnic minorities cadres training plan . To carry out the eighth batch of municipal organs attachment ca
30、dre management, selection, training work. The outstanding cadres to start the National Development Bank XX branch testing exercise.(five) to strengthen the group construction. The main position to play the role of Youth League cadre education and training as the city, in accordance with the requirem
31、ents of post training, further curriculum scientifically and rationally, adopt arrangement menu course, basic theory includes group work, focus, hot and difficult issues, to enhance the content and practice; to strengthen the construction of teaching staff, the integration of teachers, establish a q
32、uality teacher training team, establish and implement course evaluation system; take delivery of training to the countryside, on-site training, and increase the rural grassroots cadres training efforts.Four, efforts to strengthen the work of young talent(a) to tenth XX young 54 medal in recognition
33、of the publicity, and actively explore the XX youth service. 54 Medal of institutionalization, standardization and socialization mechanism. Give full play to the XX award in recognition of 54 youth medal Association, Youth Award winner in the 54 chapter, investigation activities. Who won the Youth S
34、ervice medal, dedication to the society to create conditions, build the stage. During the 54, named in recognition of the tenth XX young 54 medal. The association of XX editing of young talent , the exchange of information and communication platform for the XX of outstanding young talents.(two) the
35、establishment of municipal Party committee of young talent information database. In accordance with the feasible, effective, classification management, implement step by step principle, the establishment of municipal Party committee of youth talent database; guiding organizations at various levels g
36、enerally established the young talent database, construction of city, county (directly under the Communist Youth League), grassroots organizations three young talent information database the relevant information collection system, and gradually establish the citys young people, the Communist Youth L
37、eague youth talent information network, provide information platform for young talent resource development.Five, take effective measures to strengthen the mission management(a) to strengthen the mission management work. Strengthen the dues collection and management, continue to adhere to the dues co
38、llection regularly reporting system, the annual comprehensive award in recognition of the tour and the tour one vote veto system audit system. Do statistical work in the group. The group service award in recognition of the advanced units, standardization, promoting group management work institutiona
39、lized.(two) to strengthen the organization of research and information exchange efforts. Grassroots carry out research, efforts to form a number of theoretical results. Make full use of the network carrier, to explore the establishment of electronic group service system, promote the work of Communis
40、t Youth League information.Attachment 4:XX municipal Party Committee Propaganda Department of the Communist Youth League work pointsIn 2006, the Communist Youth League propaganda ideological work XX to Deng Xiaoping theory and the important thought of Three Represents as guidance, study and implemen
41、t the partys sixteen and the spirit of the the fifth Plenary Session of the 16th CPC Central Committee implementation of the eight plenary session of the two committee, the citys cultural work conference, the Propaganda Department of the meeting and the the fourth Plenary Session of the 15th CPC Cen
42、tral Committee permanent mission spirit, closely around 11th Five-Year XX the goal of full implementation of Scientific Outlook on Development, emancipating the mind, seeking truth from facts, keep pace with the times, close to reality, close to life, close to the young, persevere grasp orientation,
43、 grasping deepening, grasping construction innovation, further improve the groups propaganda and ideological work ability, unity To guide the majority of members of the youth to achieve the 11th Five-Year planning tasks, the overall construction of a well-off society, building a socialist harmonious
44、 society to make new contributions.One, adhere to the Three Represents important thought and Scientific Outlook on Development education to guide the youth, to further strengthen the ideological and political education of youth(a) armed with youth science theory. Unremittingly with Deng Xiaoping the
45、ory and the important thought of Three Represents armed members of youth education, to promote the study and implement to expand the depth and breadth. To study and implement the important thought of Three Represents with the establishment and implementation of Scientific Outlook on Development comb
46、ine with the implementation of the requirements of constructing socialist harmonious society with Scientific Outlook on Development, carry out education as an important part of the theory of armed youth in the new period, strengthen the establishment and implementation of Scientific Outlook on Devel
47、opment education, educate and guide the youth to fully understand the great significance of establishment and implementation of Scientific Outlook on Development, in-depth understanding of the Scientific Outlook on Development era back The king, the practice foundation, basic connotation, historical status, spirit and practice requirements, a profound understanding of Scientific Outlook on Development with Marxism Leninism, Mao Zedong thought, inheriting and developing relationship between Deng Xiaoping theory and the important thought of Three Represents, to help young people establish and