钢筋混凝土管（RCP）因具有刚度大、强度高和经济性好等优势，在全球给排水工程中得到了广泛应用。以中国为例，截至2021年，全国供水与排水管道总长度已达193.2万公里，其中超半数为混凝土或钢筋混凝土管道。然而，在钢筋混凝土管道长期服役过程中，受外部荷载、环境侵蚀及材料老化等多重因素耦合作用影响，易发生变形、腐蚀、渗漏乃至结构失效等病害，使其服役性能持续劣化。作为保障城市正常运行的重要“生命线”工程，给排水管道的健康状况直接关系到供水安全、排水防涝能力以及城市公共安全。因此，需及时对病害管道进行修复。 Reinforced concrete pipes (RCPs) exhibit high stiffness, strength, and cost-effectiveness, making them widely utilized in water supply and drainage engineering projects worldwide. In China, as of 2021, the total length of water supply and drainage pipelines has reached approximately 1.932 million kilometers, with more than half of these pipes made of concrete or reinforced concrete. However, during their long-term service life, these reinforced concrete pipes are subject to various forms of deterioration due to factors such as load effects, environmental corrosion, and material aging. Such deterioration phenomena include deformation, corrosion, leakage, and failure. As a vital "lifeline" for urban safety and operations, the health status of these pipelines directly impacts water supply security, drainage and flood prevention, and urban public safety. Consequently, the damaged pipes require prompt repair to mitigate further operational risks. 论文题目： Study on mechanical properties of self-prestressed prefabricated lining pipe for trenchless rehabilitation of large diameter underground pipelines 作者信息：Jianghao Ji; Zhiqiang Dong*; Yunfei Zhang; Hong Zhu; Shitong Hou; Jianhua Fan 期刊名称：《Tunnelling and Underground Space Technology》 近年来，随着城市地下管网老化问题日益凸显，非开挖修复技术因施工扰动小、对居民生活、城市交通和地表环境影响小而备受关注，已逐渐成为地下管道修复的重要技术路径。按照修复后对原有管道承载能力恢复程度的不同，非开挖修复技术通常可分为非结构性修复、半结构性修复和结构性修复三类 [1,2] 。其中，结构性修复技术要求修复层可独立承担外荷载。 Trenchless rehabilitation technologies have received extensive attention in recent years due to their minimal impact on residents’ daily lives, urban traffic, and ground surface environments, and have become an important approach for underground pipeline repair. According to the degree of restoration of the original pipeline bearing capacity, trenchless rehabilitation methods can be categorized into three types: non-structural rehabilitation, semi-structural rehabilitation, and structural rehabilitation [1,2] . Among them, structural rehabilitation techniques require the new liner to independently sustain external loads. 然而，对于出现结构性病害的管道，为满足既定修复效果，通常需要较厚的修复层，不可避免地带来较大的过流断面损失。因此，本文提出了一种基于Fe-SMA筋增强UHPC薄管片的非开挖修复技术。该方法旨在结构性病害的管道内部拼装预制管片，配合后注浆工艺，形成一层新的具有高承载、耐久性能的内衬管，如图1所示。基于UHPC较高的力学性能，内衬管道可以采用更薄的结构形式。Fe-SMA产生的主动预应力可进一步提高UHPC的抗拉性能，延缓UHPC基体开裂从而提高结构整体的耐久性 [3,4] 。 However, for pipelines with structural defects, achieving the desired rehabilitation performance usually requires a relatively thick repair liner, which inevitably results in a significant loss of flow area. Therefore, this study proposes a trenchless rehabilitation technique based on prefabricated Iron-based shape memory alloy (Fe-SMA) reinforced Ultra-high performance concrete (UHPC) segments. The proposed method aims to assemble prefabricated segments within structurally damaged pipelines to form a new, high-load-bearing lining pipe, as depicted in Fig. 1. The active prestress generated by Fe-SMA can further enhance the tensile performance of UHPC and delay cracking in the UHPC, thereby improving the overall durability of the structure [3,4] . 为研究预制装配式内衬管的力学性能，本文以预制管片及后注浆层为研究对象，参考 GB/T 16752-2017《混凝土和钢筋混凝土排水管试验方法》 [5] 开展了三边加载试验。进一步研究了不同混凝土材料、拼装方式及是否施加预应力等因素对装配管力学性能的影响。在此基础上，分析了这种新型预制装配式内衬管的裂缝发展规律、破坏模式、荷载-位移曲线、开裂荷载和峰值荷载。 To investigate the mechanical properties of prefabricated lining pipes, this study focuses on the prefabricated segments and post-grouting layers, conducting three-edge bearing tests in accordance with GB/T 16752-2017 [5] . The effects of various concrete materials, assembly methods, and the presence or absence of prestress on the mechanical properties were also investigated. A comprehensive analysis was performed to investigate the crack development patterns, failure modes, load-displacement curves, cracking loads, and peak loads of the novel prefabricated lining pipes. 图1新型非开挖修复技术示意图 Fig.1. Schematic of the novel trenchless rehabilitation concept and technology 本试验采用了普通混凝土和UHPC两种混凝土类型，浇筑均使用P.I 42.5水泥、Elkem 940 硅灰、S95矿粉和Sika 530P 高效减水剂。在常温条件下养护28天后，普通混凝土和UHPC的抗压强度分别为49±3 MPa和105±5 MPa，抗拉强度分别为2.59±0.3 MPa和8.2±0.4 MPa。 This experiment used two concrete types: ordinary concrete (OC) and UHPC. Both mixes used P.I 42.5 cement, 940 silica fume, S95 slag, and Sika 530P superplasticizer. After a 28-day cure in ambient conditions, the compressive strengths of OC and UHPC cubes were 49 ± 3 MPa and 105 ± 5 MPa, respectively, and the tensile strengths were 2.59 ± 0.3 MPa and 8.2 ± 0.4 MPa, respectively. 试验中所使用的普通钢筋为热轧带肋钢筋（HRB400），公称直径为10 mm。Fe-SMA筋由富佰新材料（浙江）有限公司生产，其表面形貌与普通钢筋基本一致。试验中所有Fe-SMA筋均经过酸洗并拉伸至6%预应变，拉伸后Fe-SMA筋的基本力学性能如表1所示。此外，具有6%预应变的Fe-SMA筋在200℃的激活温度下能够产生330 MPa的回复应力。 The ordinary steel rebars used in this experiment are hot-rolled ribbed steel bars (HRB 400) with a nominal diameter of 10 mm. The Fe‑SMA rebars, manufactured and supplied by Fusteel Co., Ltd., Huzhou, China, have the same surface profile as the ordinary rebars. The Fe‑SMA rebars were pickled and pre‑stretched to 6% strain. The mechanical properties of the 6% pre-strained Fe-SMA are listed in Table 1. When the 6% pre-strained Fe-SMA rebars used in this experiment were in the constrained state, a self-prestress of 330 MPa could be generated at an activation temperature of 200℃. 表1 Fe-SMA筋力学性能 Table 1. Mechanical properties of Fe-SMA rebars 试件制作过程如图2所示，共包括6个步骤。1）将Fe-SMA筋两端车出螺纹，并加工至指定弯折半径；2）组装钢模具；3）浇筑混凝土。浇筑完成脱模后管片如图2（c）所示；4）激活自预应力。需要激活自预应力的试件在常温环境中养护28d，随后在蒸压釜200℃及1.6MPa的高温高压环境中放置3小时。（需要注意的是，在自然环境中养护28天后激活Fe-SMA自预应力的原因是为了防止早期蒸压养护阶段之后UHPC的强度发生变化，为试验引入不必要的变量。在实际生产中，Fe-SMA筋可与UHPC的高温养护同时进行。）；5）组装管片。管片组装过程如图2（e）（f）所示；6）注浆。注浆过程及试件最终形貌如图2（g）（h）所示。 The fabrication process of the specimens is illustrated in Fig. 2 and consists of six steps, detailed as follows: a). The ends of the Fe‑SMA/steel rebars are machined with threads, are then bent to the designated radius. b). Steel formwork assembly. c). Concrete casting and form removal. The segment specimens are shown in Fig. 2(c). d). Self-prestress activation. Post demolding, the prestressed segments are cured in ambient conditions for 28 days. Subsequently, they are placed in an autoclave condition at 200°C and 1.6 MPa for 3 hours to activate the SME of the internal Fe‑SMA rebars and induce self‑prestress. (It should be noted that the prestressed segments are activated via autoclaving after 28 days of ambient condition curing. This approach is employed to prevent strength changes in UHPC after autoclave curing in the early stage, which could introduce extraneous variables into the experiment. In practical production, Fe‑SMA rebars can be activated combined with autoclave curing of UHPC.) e). Assembly of specimens. The assembly process of segments is shown in Figs. 2(e) and 2(f). g). Grouting. The specimens, assembled from five rings, were placed into the wooden formwork shown in Fig. 2(g). The final form of the specimen is shown in Fig. 2(h). 图2 试件制作：（a）钢筋预处理；（b）钢模具组装；（c）混凝土浇筑并脱模；（d）自预应力激活；（e）管片组装；（f）不同组装形式管片；（g）注浆；（h）试件制作完成 Fig.2. Preparation process of test specimens: (a) rebar pre-processing; (b) steel formwork assembly; (c) concrete casting and form removal; (d) self-prestress activation; (e) assembly of segment;(f) different assembly method; (g) grouting; (h) after grouting 本次试验以预制拼装管片和后注浆层组成的整体结构作为研究对象，共设计了如下参数:混凝土类型（普通混凝土和UHPC）、拼装方式（通缝和错缝）、钢筋类型（钢筋和Fe-SMA筋）以及是否激活Fe-SMA筋。试件命名如表2所示，其中“N”代表普通混凝土，“U”代表UHPC，“S”代表钢筋，“F”代表Fe-SMA筋，“A”代表通缝拼装，“B”代表错缝拼装，数字代表自预应力水平（单位：MPa）。 In this experiment, only the integrated structure consisting of prefabricated segments and the post-grouting layer was selected as the experiment subject. A total of five specimens were designed in this experiment to study the effects of concrete type (OC and UHPC), joint configuration (straight and staggered), rebar type (steel rebars and Fe‑SMA rebar), and activation of Fe‑SMA rebar or not on the performance of prefabricated pipes. The specimen numbers are shown in Table 2, where “N” represents OC, “U” represents UHPC, “S” represents steel rebars, “F” represents Fe‑SMA rebars, “A” represents straight ‑joint, “B” represents staggered‑joint, and number represents the self-prestress level in MPa. 表2 试件参数设置 Table.2 Parameter design of the specimens 如图3所示，本试验参考 GB/T16752-2017采用了三边加载测试方法，加载速率为37.5 N/s。试件上方为1500 mm的钢分配梁，分配梁与试件之间有一20 mm厚橡胶垫。下部支座由两块硬木制成，间距为管道外径的1/12，即83 mm。硬木与管道接触位置的弧形表面半径为12.5 mm。位移计分别布置在管顶，管底以及两侧起拱线。应变片分为纵向和环向两种类型，布置方式如图4所示。 This experiment was conducted with reference to GBT16752-2017, utilizing a three-edge loading test. The load was applied with a loading rate of 37.5 N/s, and the loading configuration is shown in Fig. 3. During the experiment, a steel distribution beam with a length of 1500 mm was placed above the specimen, and a 20 mm thick rubber pad was placed between the distribution beam and the specimen. The lower support was made of two hardwoods, with a spacing of 1/12 of the pipe outer diameter, i.e., 83 mm. The radius of the arc surface at the contact position between the hardwood and the pipe was 12.5 mm. Strain gauges were categorized into two types: longitudinal and circumferential. The arrangements of strain gauges are depicted in Fig. 4. 图3 试验装置及设备 Fig.3. Test setup and instrumentations 图4 应变片布置方式：（a）通缝试件；（b）错缝试件 Fig.4. Strain gauge arrangement scheme: (a) specimens with straight-jointed; (b) specimens with stagger-jointed 试件的破坏模式如图5所示。所有试件均表现出相似的裂缝发展模式：第一条裂缝均始于管顶或管底，随着荷载的增加，裂缝的数量和长度也随之增加。随后，在外侧起拱线位置出现裂缝，如图5（a）所示。随着进一步加载，裂缝逐渐贯穿整个试件。除U-S-B外，其余试件的破坏模式均为底部/顶部钢筋无法继续承担荷载，结构竖向变形激增。由于U-S-B采用错缝拼装形式，其破坏模式与U-S-A和N-S有所不同。这是由于错缝拼装会使相对薄弱的后浇区域处于弯矩较大的位置（管顶/管底），从而导致过早开裂。因此，在U-S-B的起拱线内侧也观察到了明显的裂缝，如图5（c）所示。 The failure modes are shown in Fig. 5. All specimens exhibited similar crack propagation patterns: the first crack initiated at the crown or invert, and both crack number and length increased with applied load. Subsequently, cracks appeared in the grout at the external springline, as shown in Fig. 5(a). With further loading, cracks propagated through the entire specimen. Failure is characterized by a sudden surge in vertical deformation when the rebars at the invert or crown can no longer bearing the load. The failure mode of U‑S‑B, assembled using staggered joints, differs slightly from those of U‑S‑A and N‑S. This is because staggered assembly will place the relatively weak post-cast areas at locations of high bending moment (crown/invert), causing premature cracking. Consequently, pronounced cracks were observed at the inner springline of U‑S‑B, as shown in Fig. 5(c). 图 6 所示为试件荷载-竖向位移曲线及荷载-水平位移曲线。荷载-位移曲线可分为三个不同的阶段：线性上升段、非线性上升段及下降段。U-S-B的非线性上升和下降段明显长于其它试件，这表明其延性更好。此外，由于自预应力效应的存在，U-F-300的初始刚度高于其余试件。由于Fe-SMA筋具有比HRB400钢筋更高的屈服强度和极限强度，U-F-0和U-F-330的峰值荷载也较高。 Fig. 6 illustrates the load-vertical displacement curves and the load-lateral displacement curves of test specimens. As depicted in Fig. 6, the curves can be divided into three distinct stages: a linear ascending segment, a non-linear ascending segment, and a descending segment. The nonlinear ascending and descending segments of U‑S‑B are markedly longer than those of the other specimens, indicating greater ductility. In addition, U‑F‑300 exhibits higher stiffness than the other specimens, which can be attributed to self‑prestressing effects. Owing to the higher yield and ultimate strengths of the Fe‑SMA rebars, specimens U‑F‑0 and U‑F‑330 exhibited higher ultimate strength. 图5 破坏模式:（a）N-S；（b）U-S-A；（c）U-S-B；（d）U-F-0；（e）U-F-330 Fig.5 Failure modes: (a) N-S; (b) U-S-A; (c) U-S-B; (d)U-F-0; (e)U-F-330 图6 荷载-位移曲线：（a）竖向位移；（b）水平位移 Fig.6 Load-displacement curves: (a) vertical displacement; (b) lateral displacement 图7所示为试件的环向应变-荷载曲线。图7中纵轴表示环向应变的大小，中心为 0，沿图半径方向逐渐增大。如图7所示，所有试件的应变分布均呈现出管顶/管底较大，起拱线位置次之，其余位置较小，大致呈菱形分布的特征。进一步对比发现，U-F-330试件的应变分布形态更为狭长，起拱线处的应变明显低于管顶和管底。结合第4.2节的结果可知，U-F-300试件的水平位移同样小于其余试件。这表明，自预应力的引入在一定程度上提高了管片刚度，抑制了装配管横向变形的发展。但这一现象可能会导致两侧管片的材料性能无法完全发挥。 Fig. 7 presents the circumferential strains observed in each specimen. The vertical axis represents the magnitude of strain in the radial direction, with a center of 0, gradually increases along the radial direction. Fig. 7 reveals that the strain distribution across all specimens exhibits higher values at the crown/invert, lower values at the springlines, and a roughly diamond-shaped pattern. Comparatively, it can be observed that the strain distribution of the U-F-330 specimen is more elongated, with the strain at the springline being significantly lower than that at the crown/invert of the pipe. As demonstrated in Section 4.2, the lateral displacement of the U-F-300 specimen was also smaller than that of the other specimens. This behavior is attributed to the self-prestressing effect, which enhances the stiffness of the specimen, thereby reducing its tendency for lateral deformation. However, this phenomenon may also lead to a reduction in the full utilization of the mechanical properties of the segments on both sides. 图7 应变分布：（a）N-S；（b）U-S-A；（c）U-S-B；（d）U-F-0；（e）U-F-330 Fig.7 Strain distribution: (a) N-S; (b) U-S-A; (c) U-S-B; (d) U-F-0; (e) U-F-330 GBT16752-2017中规定，裂缝宽度为 0.2 mm时所对应的荷载为管道的开裂荷载。因此，试验通过裂缝观测仪记录了不同试件0.2 mm裂缝时所对应的荷载大小。表 3和图 8给出了不同试件第一条裂缝出现时荷载（Fc）、0.2 mm裂缝宽度时荷载（Fc,0.2）、峰值荷载（Fu）以及峰值荷载对应的位移（Δu）。通过对比N-S和U-S-A试件可以看出，提高混凝土强度显著增强了装配管的力学性能。采用UHPC后，试件的初裂荷载、0.2 mm裂缝宽度时荷载以及峰值荷载分别提高了36.4%、14.3%和22.4%。 According to GBT16752–2017, the load corresponding to a crack width of 0.2 mm is taken as the cracking load for pipes. Therefore, the load at a 0.2 mm crack is of particular significance for structural performance. Table 2 and Fig. 8 present the cracking load at the first crack (Fc), the load at a 0.2 mm crack width (Fc, 0.2), the peak load (Fu), and the displacement corresponding to the peak load (Δu) for the different specimens. Comparison of N‑S and U‑S‑A indicates that increasing concrete strength markedly enhances all specimen performance. After using UHPC, the specimen cracking load, load at 0.2mm crack width and peak load increased by 36.4%, 14.3% and 22.4% respectively. 表3 特征值汇总 Table.3 Summary of characteristics value. 相比于采用通缝拼装的试件，采用错缝拼装后，试件的初裂荷载和峰值荷载从27.0 kN和79.8 kN降低至21.1 kN和72.1 kN，分别减小了21.8%和9.6%。值得注意的是，U-S-B的峰值位移增加到55.5 mm，比U-S-A大35.7%，这证明采用错缝拼装的方式增强了结构的变形能力但降低了初裂荷载和峰值荷载。U-F-0的峰值荷载比U-S-A增加了13.2%，而其初裂荷载基本保持不变。这表明使用高强筋能够提高构件的峰值荷载，但对初裂荷载几乎没有影响。Fe-SMA回复应力被激活后，试件峰值荷载基本保持不变，但初裂荷载及0.2 mm裂缝宽度时荷载显著提高。U-F-0和U-F-330的初裂荷载分别为27.4 kN和37.7 kN，而在0.2 mm裂缝宽度时荷载分别为44.0 kN和52.5 kN，激活自预应力后分别提高了37.6%和19.3%。这些结果证明，Fe-SMA筋的自预应力可显著增强试件的抗裂性能。 When adopted with the staggered assembly method, the specimens’ cracking and peak loads decreased from 27.0 kN and 79.8 kN to 21.1 kN and 72.1 kN, a decrease of 21.8% and 9.6%, respectively. Notably, the peak displacement of U-S-B increased to 55.5 mm, 35.7% greater than U‑S‑A, indicating enhanced deformability due to the staggered post-cast areas. U‑F‑0 showed a 13.2% increase in peak load compared with U‑S‑A, while its cracking load remained essentially unchanged. This indicates that the use of high-strength steel rebar can increase the ultimate load, but has almost no effect on cracking loads. After activation of the Fe‑SMA rebars, the peak load remained similar, but prestress substantially increased both the cracking load and the load at a 0.2 mm crack width. The cracking loads for U‑F‑0 and U‑F‑330 were 27.4 kN and 37.7 kN, and the corresponding loads at 0.2 mm crack width were 44.0 kN and 52.5 kN, enhancements of 37.6% and 19.3% after activating the self-prestress, respectively. These results confirm that the self-prestress of Fe-SMA rebars markedly improves the specimens’ cracking resistance. 图8关键性能参数值 Fig. 8 Load-bearing characteristics values 本文提出了一种用于大直径地下管道非开挖修复的新型预制装配式内衬管结构。通过试验研究了这种新型装配式内衬管的失效模式和力学性能。结果表明，内衬管中的首条裂缝均出现在管顶或管底。此外，结构的失效伴随着管顶或管底钢筋屈服。加载过程中环向应变分布呈菱形，即管顶/管底最大，起拱线次之，其余位置较小。在自预应力的作用下，菱形变得更为狭长。自预应力的激活对峰值荷载几乎没有影响，但显著增加了初裂荷载。预应力激活后，试件的初裂荷载分别从 27.4 kN增加至37.7 kN，0.2 mm裂缝宽度对应的荷载从 44.0 kN增加至 52.5 kN，分别增加了37.6%和19.3%。 This paper proposes a novel lining prefabricated pipe structure for trenchless rehabilitation of large-diameter underground pipelines. Through experimental investigations, the failure modes and mechanical performance of this new lining assembly pipe are revealed. The results show that the first cracks in the assembly pipe uniformly appeared at the crown or invert. Moreover, the pipe failure was accompanied by yielding of the rebar at the crown or invert. The circumferential strain distribution generally displayed a diamond-shaped pattern, with the shape becoming more elongated in the case of prestressed assembled pipes. Activation of the self-prestress had little effect on the peak load but significantly increased the cracking load. Prior to and following prestress activation, the cracking loads of the specimens were 27.4 kN and 37.7 kN, respectively, and the loads at a 0.2 mm crack width increased from 44.0 kN to 52.5 kN, representing an increase of 37.6% and 19.3%, respectively. [1] Li, B., Yu, W., Xie, Y., et al. (2023). Trenchless rehabilitation of sewage pipelines from the perspective of the whole technology chain: A state-of-the-art review. Tunnelling and Underground Space Technology, 134. [2] Xi, D., Lu, H., Zou, X., et al. (2024). Development of trenchless rehabilitation for underground pipelines from an academic perspective. Tunnelling and Underground Space Technology, 144. [3] Dong, Z., Ji, J., Liu, Z., et al. (2024). A feasibility study on improving the crack resistance of thin-walled UHPC members by reinforcement with Fe-SMA wires. Journal of Sustainable Cement-Based Materials, 14(1), 103–118. [4] Cui, C., Dong, Z., Zhu, H., et al. (2025). Axial compressive behavior of UHPC columns reinforced with self-prestressed Fe-SMA spiral stirrups. Structures, 77. [5] Standardization Administration of China. GBT16752–2017: Test Method for Drainage pipes of Concrete and reinforced concrete. (2017). In. China. 资料来源：东南大学Fe-SMA自预应力技术研发团队 |
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