沥青基灌浆技术在后张预应力结构中的应用及试验研究

发布时间：2018-06-16 21:31

  本文选题：后张法预应力结构 + 灌浆泌水　； 参考：《北京交通大学》2015年博士论文

【摘要】：在土建行业后张结构体系中,浆体是保证预应力筋免遭腐蚀的最后一道防线。预应力孔道的灌浆作用在于对预应力筋进行防腐保护,并提供预应力筋与孔道周围混凝土之间的粘结力。这些目标实现的前提是预应力孔道完全被浆体所灌满,但浆体泌水的存在使孔道灌浆完全密实变得十分困难,孔道灌浆不密实而导致预应力体系的腐蚀是后张体系中一直存在的问题。本文提出了两项防治灌浆泌水的措施,重点研究了以无泌水的沥青基材料替代水泥基材料进行灌浆的技术,通过对其材料配合比、可灌性、对预应力损失的影响规律以及与预应力筋的粘结性能等方面的研究,实现了沥青基灌浆技术在后张预应力结构中的应用。本文的主要研究内容和成果概括如下：(1)现有灌浆工艺和材料的灌浆试验结果表明,预应力孔道内都会出现灌浆不密实的现象。探讨了水泥浆体泌水的过程和减小泌水的措施,以改进预应力孔道结构层次为出发点,开发出一种组合橡胶棒以成型带垭口预应力孔道,研究了其解决浆体泌水危害的机理。以高速铁路32m简支箱梁为原型,设计并进行了足尺预应力孔道灌浆密实性对比试验。结合试验,深入分析了浆体泌水在孔道中产生、传输和分布的特性,研究了孔道弯起高度对灌浆密实率的影响规律。试验结果表明,使用带垭口孔道能够使浆体泌水形成的空洞与预应力筋相分离,避免预应力筋遭受腐蚀,对于后张结构中的平直和具有一定弯起角度的预应力孔道,带垭口孔道的灌浆密实性远优于圆形孔道。(2)确定了沥青基灌浆材料的设计目标和试验方案。经过初步试验,确定了岩沥青为基质沥青的改性沥青,其掺加比例为12.5%。在此基础上,通过对不同配合比沥青基灌浆材料的粘度试验、粘温变化规律研究及抗剪强度试验,得到沥青基灌浆材料的配合比为：基质沥青+岩沥青(12.5%)+(消石灰：水泥=1：9)(40%),该配合比下沥青基灌浆材料的常温抗剪强度为697.21 kPa,其可灌温度应高于115℃。以增加消石灰掺量和添加纤维为途径,得到改进型沥青基灌浆材料配合比为：基质沥青+岩沥青(12.5%)+(消石灰：水泥=3：7)(40%)+纤维(1%),该改进型沥青基灌浆材料的抗剪强度约为普通型的2倍,其可灌温度应高于140℃。(3)推导了沥青基材料在孔道中的对流换热系数理论计算公式,建立了灌浆试验梁有限元模型,通过对灌浆过程的模拟计算,确定了灌浆工艺关键参数为：合适的灌浆流量为50 L/min;合理的灌浆温度为：入口温度为160℃、壁面温度为60℃；合适的灌浆压力为0.8 MPa。通过对试验梁及外挂预应力孔道的现场灌浆试验,验证了沥青基灌浆材料的灌浆工艺参数的正确性和灌浆效果的有效性。(4)通过对采用沥青基材料灌浆的混凝土梁温度场及应力场的计算可得,预应力孔道的成孔材料应选择HDPE材质,灌浆时间是影响温度场和应力场的最主要参数,文中给出的各浆体温度下,混凝土的最大拉、压应力均小于规范规定值。与混凝土梁温度场和应力场的实测数据对比可得,本文计算值与温度场实测值的误差小于10%,与应力场实测值的误差小于15%,表明本文的计算结果准确有效。建立了沥青基材料灌浆适用性方程,可得出不同强度等级混凝土在不同浆体温度下的安全灌浆时间,从而为采用沥青基材料的后张结构灌浆施工提供依据。(5)通过试验可得,浆体温度下预应力钢绞线各项力学性能均可达到原指标值的0.9倍,应力松弛最大可达6.36%。浆体温度作用后,其力学性能指标可恢复到原指标值的0.965倍以上,应力松弛最大为1.71%。根据试验结果,得到了浆体温度作用下及作用后的预应力钢绞线力学性能退化模型和应力松弛计算模型。建立了由浆体温度引起的短期和长期预应力损失模型,与现场预应力实测结果对比,最大误差为14.1%,验证了该模型的准确性。通过计算可得,沥青基材料灌浆最不利工况下产生的长期预应力损失率为2.73%。(6)在沥青基灌浆材料粘弹性本构关系基础上,推导出预应力筋-沥青基材料粘结受力理论解,得到了钢绞线、钢绞线-基体界面以及沥青基材料基体等的应力分布特征。探讨了施加荷载、预应力筋与基体的半径比、沥青基材料温度以及荷载施加时间等因素对预应力筋-沥青基材料之间粘结性能的影响规律。通过与已有成果的对比,验证了本文所推导公式的正确性。计算结果表明,在短期荷载作用下,采用沥青基灌浆材料灌浆的后张预应力结构可按有粘结预应力结构进行计算,在长期荷载作用下,需按无粘结预应力结构进行计算。
[Abstract]:In the post tensioning system of civil engineering, the slurry is the last line of defense to ensure that the prestressing tendons are not corroded. The grouting effect of the prestressing force is to protect the prestressed reinforcement and provide the bond between the prestressed reinforcement and the concrete around the pass. The premise is that the prestress channel is completely filled by the slurry. Full, but the presence of water in the slurry makes it very difficult to complete the grouting of the channel, and the failure of the pore grouting is a problem in the post tensioning system. In this paper, two measures to prevent and control the bleeding of the grouting are put forward, and the grouting is focused on the substitute of the cement based material instead of the bituminous base material. The application of asphalt based grouting technology in the post tensioned prestressed structure is realized through the study of the mixture ratio of materials, irrigability, the influence of the loss of prestress and the bonding performance of prestressing tendons. The main contents and achievements of this paper are as follows: (1) the grouting test knot of the existing grouting technology and material The results show that the grouting is not dense in the prestress channel. The process of water secretion and the measures to reduce the bleeding are discussed. In order to improve the structure level of the prestress channel, a combination of rubber bars is developed to form the prestress channel of the belt pass, and the mechanism to solve the harm of the bleeding of the slurry is studied. On the basis of the prototype of the simple supported box beam of road 32m, a full scale grouting compactness test was designed and carried out. Combined with the test, the characteristics of the production, transmission and distribution of the slurry in the channel were analyzed, and the influence of the height of the pass on the density of the grouting was studied. The experimental results showed that the use of the pass through the pass can make the slurry secreted. The hole formed by the water is separated from the prestressed reinforcement to avoid the corrosion of the prestressing tendons. For the post tensioned structure, the grouting density of the tunnel with the pass is far superior to the circular channel. (2) the setting target and the test plan of the asphalt base grouting material are determined. After preliminary test, it has been determined. The asphalt based asphalt is modified bitumen. On the basis of the addition ratio of 12.5%., the mixture ratio of asphalt based grouting material is obtained by the viscosity test of different mixture ratio asphalt base grouting material and the shear strength test. The mixture ratio of asphalt base grouting material is: matrix asphalt + rock bitumen (12.5%) + (40%) (cement: cement) (40%). The shear strength of the asphalt based grouting material at normal temperature is 697.21 kPa, and its irrigation temperature should be higher than 115. In order to increase the dosage of lime and add fiber, the mixture ratio of the improved asphalt base grouting material is: matrix asphalt + rock bitumen (12.5%) + (water sludge =3:7) (40%) + fiber (1%), and the improved asphalt base grouting The shear strength of the material is about 2 times that of the common type, and its irrigation temperature should be higher than 140. (3) the theoretical calculation formula of the convection heat transfer coefficient of the asphalt based material in the pass is derived. The finite element model of the grouting test beam is established. The key parameters of the grouting process are determined by the simulation calculation of the grouting process. The appropriate grouting flow rate is 50 L/. Min, the reasonable grouting temperature is: the inlet temperature is 160, the wall temperature is 60, and the appropriate grouting pressure is 0.8 MPa. through the field grouting test of the test beam and the external prestressed concrete pass. The correctness of the grouting process parameters and the effectiveness of the grouting effect are verified. (4) through the use of asphalt base material irrigation. The calculation of the temperature field and stress field of the concrete beam of the slurry can be obtained. The pore forming material of the prestressed concrete pass should be selected as the HDPE material. The time of the grouting is the most important parameter affecting the temperature field and the stress field. Under the temperature degree of each slurry given in this article, the maximum tension of concrete is less than the prescribed value of the gauge. The error between the measured data and the measured data is less than 10%, and the error of the measured value of the stress field is less than 15%. It shows that the calculation results of this paper are accurate and effective. The applicability of the asphalt base material grouting is established, and the safety grouting time of different strength grade concrete under the different temperature is obtained. The post tensioning construction of asphalt based material can be used as a basis. (5) through the test, the mechanical properties of the prestressed steel strand under the slurry temperature can reach 0.9 times that of the original index. After the maximum stress relaxation can reach the 6.36%. slurry temperature, the mechanical properties can be restored to more than 0.965 times of the original index, and the stress relaxation is the greatest. Based on the test results, the mechanical properties degradation model and stress relaxation model of prestressed steel strand under and after the action of slurry temperature are obtained. The short-term and long term prestress loss model caused by the slurry temperature is established. The maximum error is 14.1% compared with the field prestress test results, which verifies the accuracy of the model. On the basis of the viscoelastic constitutive relation of asphalt based grouting material, the theoretical solution of bond stress of prestressed reinforcement and bituminous base material is derived by calculation. On the basis of the viscoelastic constitutive relation of asphalt based grouting material, the loss rate of long term prestress produced in the most unfavorable condition of asphalt base material grouting is 2.73%. (6). The stress of steel strand, steel strand matrix interface and asphalt base material base are obtained. The influence of the load, the radius ratio of the prestressed reinforcement and the matrix, the temperature of the bituminous material and the loading time on the bond performance between the prestressed reinforcement and the bituminous base material is discussed. The validity of the formula is verified by the comparison with the existing results. The calculation results show that the short-term load is used in the short term load. Under the action, the post tensioned prestressed structure using the grouting material of asphalt base grouting material can be calculated according to the bonded prestressed structure. Under the long term load, it is necessary to calculate the unbonded prestressed structure.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U444;U446
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本文编号：2028178