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1、渠道防渗工程中的技术措施初探杨普义（山西省汾河水利管理局，祁县 030900）摘要： 汾河灌区是山西省最大的自流灌区，控制灌溉面积9.97万 hm2。渠道防渗是灌区节水的主要技术手段。文中在近几年来渠道防渗工程施工和管理经验基础上，分析了砼面板破坏的类型及原因，提出了修复措施。关键词：渠道； 防渗； 技术措施中图分类号：TV543 文献标识码：B汾河灌区的灌溉渠道基土多为冻胀土，地下水含盐量又较高，所以在对渠道进行砼面板防渗设计中，如何有效避免渠道砼板的破坏问题，成了灌区节水改造是否成功的关键。结合本灌区实际，本文将对渠道砼面板产生破坏的类型、原因及修复措施进行分析介绍，以期对以后的渠道防渗设
2、计有所帮助。 1.渠道砼面板破坏的类型通过对灌区大量砼板防渗渠道坡坏现象的分析，按其破坏状态大致可分为以下两种：一种是砼面板破裂，翘起，滑落，严重的渠道边坡塌陷，在此类破坏过程中，砼本身的强度、抗冻、抗渗等指标改变很小或没有发生改变，仅是砼面板的整体结构受到破坏，如一坝太钢支渠的600m砼防渗及东干二支近3km的砼板防渗破坏型式即为之，这种破坏我们称之为冻胀破坏；另一种情况是砼面板受到侵蚀，主要是砼与土壤水中的酸类、盐类等发生化学反应，然后慢慢由外向内发展，最后砼板局部或整体产生酥松，直到砼完全失去强度，我们称之为渠道砼面板的侵蚀破坏。两种破坏形式虽不相同，但最后都将导致渠道节水功能的下降。另
3、外，随着渠道断面输水糙率不断变大，渠道的过水能力也会大大降低，严重的会导致整个渠道丧失输水功能。因此，在存在冻胀土的寒冷地区以及地下水对砼具有侵蚀性的地区，渠道防渗设计、施工及今后维修管理过程中，应充分考虑以上问题，使整个渠道防渗工程发挥最大的效益。 2.渠道砼面板破坏的原因 2.1渠道砼面板冻胀破坏的原因渠道砼面板发生冻胀破坏的原因是渠基土发生冻胀，渠基土的冻胀与以下几个因素有关：1）寒冷地区的气温是否长期低于0；2)基土中是否存在冻结的主体：水分；3）基土的物理性质，主要包括土的颗粒组成等。 2.1.1各因素间的相互关系渠基土中含有土壤水，这些土壤水主要是由土粒子间填充的自由水和吸附在粒子
4、周围的束缚水组成，自由水的多少与粒子间空隙的大小有关，束缚水的多少与土粒子总的表面积有关。针对渠道砼面板基土来说，因为其多为夯实土，粒子间隙小，所以其含水量的大小主要与粒子周围束缚水有关。而束缚水的多少又与基土的性质有关，即土质组成颗粒越细，其颗粒的比面积就越大（比面积为1g土体中所有土颗粒的表面积之和），粒子所吸附的水分也就是基土的含水量就越多。这样，当气温长时间处于0以下时，基土中水分就会结冰，根据水在结冰时体积增大0.09倍的性质，基土的体积也将增大，这将给其上的砼面板产生向上的推力，如果该力足够大，将引起砼面板在该力方向上的位移，或使板体本身发生破裂，翘起，滑落，严重的将导致渠道边坡塌
5、陷。 2.1.2冻胀基土中的水分迁移原理因为在不同土颗粒表面吸附水之间存在着电位差，当气温长时间低于0时，在该电位差和毛管水表面张力的共同作用下，土颗粒表层的活跃水分子将会顺着温度梯度方向向土壤水冻结峰面迁移，如果基土水分有充足的补给源，基土冻结锋面将会产生更为严重的冻胀。因为常规冻胀量一般为原来体积的10%50%，而在水分迁移的情况下，冻结锋面上的冻胀量可达到原来体积的数倍。在重力作用下，冻土水分垂直迁移以及毛细管水上升高度都有一定的范围，该范围的大小与土质有关，在此不再论述。 理论分析和工程实践证明，粒径大于0.1mm的基土因其所含水分较少，在其结冰时产生的膨胀力较小，不足以对砼板产生破坏
6、；当基土粒径在0.1mm0.05mm之间时，破坏较大，而当粒径在0.05mm0.002mm时，基土冻胀破坏最强。按照土质的分类，黏土的冻胀破坏最强，其次依次降低的是粉质土、亚黏土和亚砂土。 汾河灌区属太原盆地，每年冬季时间约五个月，最低气温-200C左右，00C以下每年有120天左右；其渠基土为黏土、砂壤土等，大部分灌溉渠道为挖方、半挖方渠道，因此，防渗渠道存在着较大的冻胀破坏。尤其是东西走向的渠道其阴坡较阳坡破坏更为严重。3.对于预制砼防渗层的维修措施3.1现浇砼防渗层的裂缝修复当砼防渗层发生裂缝后，如果防渗层仍大致平整，无较大错位，裂缝较小的情况，可以运用过氯乙烯胶液涂料粘贴玻璃丝布的方法
7、，进行修复。而对于裂缝较大者，可采用填筑伸缩缝的方法修复。对于大型渠道裂缝又较大的，可采用填塞与粘贴相结合的方法修复。近年来我们在二坝东干渠进行了近1km的防渗裂缝维修，具体做法如下： 1) 清除缝内、缝壁及缝口两边的泥土、杂物，保持清洁、干燥。 2) 缝壁涂刷冷底子油。 3) 将煤焦油填料或焦油塑料胶泥填入缝内，填压密实，保持表面平整光滑。 4) 填好缝12天后，沿缝口两边涂刷5cm宽的过氯乙烯涂料一层，随即沿缝口两边粘贴34cm宽玻璃丝布一层、再涂刷涂料一层、粘贴第二层玻璃丝布，最后涂刷一层涂料。在运用此方法中，注意涂料要涂刷均匀，玻璃丝布要粘平，不能有气泡。3.2预制砼防渗层的修复 3.
8、2.1砼防渗层砌筑缝的修复预制砼渠道包括板和U型槽，其砌筑缝多采用水泥砂浆缝。砼板防渗渠道的砂浆填缝一般有以下缺点：砂浆强度低；施工挤压不实；不能与砼板紧密结合，勾缝的砂浆容易脱落，有的从勾缝中长出了杂草，甚至有些小型填方渠道衬砌完后，试放水发生垮渠等破坏情况，能保持完好的工程基本很少。造成放水垮渠原因，除了土方渠道质量不好外。衬砌部分勾缝的漏水是主要的原因。为了保证工程质量，建议对砼预制板改用方形或长方形，预制板的大小应便于施工为宜，厚度810cm为好，板缝留10cm15cm用高标号砼填塞，人工机械都能施工，要求捣出浆与砼板能紧密结合，使衬砌段形成整体，基本达到现浇的质量。对于旧渠防渗层砌筑
9、缝的修复也可以这样处理：凿除缝内水泥砂浆块，将缝壁、缝口冲刷干净，用与砼板相同标号的水泥砂浆填塞，捣实抹平后，保湿养护不得少于14天。 3.2.2砼防渗层表层的修复砼防渗层表层损坏，如剥蚀，孔洞等，可采取水泥砂浆修补，有条件时可采用喷浆法修复。（1）水泥砂浆修复方法：首先必须全部除掉已损坏的砼，并对修补部位进行凿毛处理，冲洗干净，然后在工作面保持湿润的状态下，将拌和好的砂浆用木抹抹到修补部位，反复压平，用铁抹抹光后，保湿养护不少于14天。注意如果修补部位深度较大时，可在水泥砂浆中掺和适量的砾料，作用是可以减少砂浆干缩和增强砂浆强度。（2）喷浆修复方法：如果条件允许，可以采用此方法。方法是将水泥
10、、砂和水的混合料用喷浆设备经高压通过喷头喷射到修复部位。 3.3砼防渗层的翻修 3.3.1旧板拆除，重新铺筑砼防渗层如若损坏严重，例如破碎、错位，滑坍等的情况下，应拆除损坏部位，处理好地基土重新铺筑。在铺筑时要特别注意新旧砼的结合面处理好。方法是结合面凿毛冲洗后，需涂一层厚2cm的水泥净浆，才能开始铺筑新砼，同样铺筑好的砼要注意保湿养护。 3.3.2旧板不拆，加铺新板(1) 现浇砼方案：把旧砼冻胀隆起的部分压平后，在上面铺设保温板（聚苯保温板），然后铺一层塑料薄膜，完成后在其上再铺筑素砼。苯板和现浇砼的厚度通过计算得出。此种方法的优点是比较适合渠道现状，较美观。缺点：工期长，施工质量较难控制，
11、不适应工程在干渠输水间隔期施工。近几年，在灌区部分渠道上也采用此方案施工，不同的是将聚苯保温板换成了二布二膜土工布，不但降低了成本而且施工方便，节水效果良好。(2) 预制砼板方案：把旧砼冻胀隆起的部分压平后，在上面铺设保温板（聚苯保温板），然后铺一层塑料薄膜，用砂浆找平后，铺筑砼板。此种方法的优点是砼板可集中预制，砼质量易控制，集中铺砌，适应工程在干渠输水间隔期施工。缺点：砼板尺寸固定，难以适合渠道现状尺寸。作者简介：杨普义, 男, 1963年生, 1984年山西省水利学校农田水利专业毕业，2004年河海大学工程管理专业毕业（函授）收稿日期:2007-12-19Driginal Probe o
12、f Technical Measure in Canal Seepage Prevention EngineeringYANG Pu-yiAbstract：The Fenhe Irrifation District is the largest irigation district in Shanxi Province,Its control irrgation area is 9.9104hm2.Canal seepage prevention is the main technical measure of watersaving. On the basis of construction
13、 and management experiences in recent years,this paper analyzes the destruction type and cause of concrete lining and presents some repair measures.Keywords: canal seepage prevention technical measure Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with
14、CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also m
15、issed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race
16、has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the
17、New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to
18、the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist
19、and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a
20、gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverW
21、ith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as
22、 early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (t
23、he troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called
24、the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving
25、platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for th
26、e big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or
27、 spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he
28、 will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaran
29、teed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
