End Uses of Landfills (垃圾填埋场的最终用途)

Introduction 介绍

Landfills pose a number of environmental and social issues while in operation which are regulated by USEPA, state governments, and local municipalities. However, the way the land is used after the landfill reaches its capacity is an important long-term consideration for the owners of the landfill and the communities surrounding them. As the population density in an area continues to increase, the value of reclaimed land occupied by landfills also increases. According the USEPA (2014), and as demonstrated in many case studies, the long-term end use of a landfill should be considered in the original design, or at least early in the life of the landfill. Poor planning can lead to costly redesign and extra work in terms of grading and drainage planning, cover design to support foundations, gas collection and control systems, settlement mitigation, and more. Thus, foresight on how the land will eventually be used can save project owners significant funds.

垃圾填埋场在运营过程中会带来许多环境和社会问题,这些问题由美国环保署、州政府和当地市政当局监管。然而,填埋场达到其容量后土地的使用方式是填埋场所有者及其周围社区的重要长期考虑因素。随着一个地区的人口密度不断增加,填埋场占用的填海土地的价值也随之增加。根据 USEPA (2014),并且正如许多案例研究所证明的那样,垃圾填埋场的长期最终用途应在原始设计中考虑,或者至少在垃圾填埋场的早期使用。规划不善可能导致代价高昂的重新设计和在分级和排水规划、支持地基的覆盖设计、气体收集和控制系统、沉降缓解、和更多。因此,对土地最终用途的预见可以为项目所有者节省大量资金。

This paper introduces some of the most common end uses of landfills, discussing advantages and applicability of alternatives to different landfill sites and presents case studies emphasizing successes and challenges for post-closure end uses. Engineering considerations for topics discussed are presented to provide preliminary insight to what issues may be faced when choosing what to do with a landfill post-closure. The presentations of each topic in this paper are not comprehensive due to the unique nature of each landfill project. Case studies are helpful to look at because every landfill project is unique, so creative solutions are developed specific to each project. Some regulatory aspects of landfill management related to landfill gas and leachate are also discussed, but those issues are not the main focus of the paper. However, it is important to keep in mind that regardless of the end use of the landfill, standard post-closure requirements apply. This typically entails post-closure management of landfill gas and leachate control systems, and groundwater monitoring for a period of 30 years after site closure, per the Resource Conservation and Recovery Act (RCRA). However, the Interstate Technology and Regulatory Council (2006) offers guidelines for optimizing post-closure care on a performance basis, which can reduce the time period required for post-closure care. Either way, these systems must be integrated into the end use of the landfill in such a way as to protect the health and safety of people and the environment.

本文介绍了垃圾填埋场的一些最常见的最终用途,讨论了不同垃圾填埋场替代方案的优势和适用性,并提供了强调关闭后最终用途的成功和挑战的案例研究。提出了讨论主题的工程考虑因素,以初步了解在选择如何处理垃圾填埋场关闭后可能面临的问题。由于每个垃圾填埋场项目的独特性,本文中每个主题的介绍并不全面。案例研究有助于查看,因为每个垃圾填埋场项目都是独一无二的,因此针对每个项目开发了创造性的解决方案。还讨论了与垃圾填埋气和渗滤液有关的垃圾填埋场管理的一些监管方面,但这些问题不是本文的主要重点。然而,重要的是要记住,无论垃圾填埋场的最终用途如何,都适用标准的关闭后要求。根据《资源保护和恢复法》 (RCRA),这通常需要对垃圾填埋气和渗滤液控制系统进行关闭后管理,并在场地关闭后 30 年内监测地下水。然而,州际技术和监管委员会 (2006) 提供了基于绩效优化关闭后护理的指南,这可以减少关闭后护理所需的时间。无论哪种方式,这些系统都必须与垃圾填埋场的最终用途相结合,以保护人和环境的健康和安全。根据《资源保护和恢复法》 (RCRA),这通常需要对垃圾填埋气和渗滤液控制系统进行关闭后管理,并在场地关闭后 30 年内监测地下水。然而,州际技术和监管委员会 (2006) 提供了基于绩效优化关闭后护理的指南,这可以减少关闭后护理所需的时间。无论哪种方式,这些系统都必须与垃圾填埋场的最终用途相结合,以保护人和环境的健康和安全。根据《资源保护和恢复法》 (RCRA),这通常需要对垃圾填埋气和渗滤液控制系统进行关闭后管理,并在场地关闭后 30 年内监测地下水。然而,州际技术和监管委员会 (2006) 提供了基于绩效优化关闭后护理的指南,这可以减少关闭后护理所需的时间。无论哪种方式,这些系统都必须与垃圾填埋场的最终用途相结合,以保护人和环境的健康和安全。州际技术和监管委员会(2006 年)提供了基于绩效优化关闭后护理的指南,这可以减少关闭后护理所需的时间。无论哪种方式,这些系统都必须与垃圾填埋场的最终用途相结合,以保护人和环境的健康和安全。州际技术和监管委员会(2006 年)提供了基于绩效优化关闭后护理的指南,这可以减少关闭后护理所需的时间。无论哪种方式,这些系统都必须与垃圾填埋场的最终用途相结合,以保护人和环境的健康和安全。

Recreational Uses 娱乐用途

The most common end use for landfills is developing the land for recreational use. Examples of recreational uses are golf courses, nature parks, fields, and walking or biking trails for public use. These types of development are relatively easy to construct and maintain because differential settlements due to waste decomposition do not adversely affect recreational facilities like they do with buildings. However, settlement is still an issue that must be accounted for. Along with settlement and other issues ubiquitous to landfills, in any recreational end use design, capping, trees, and landscaping are critical features that must be designed and maintained carefully (Sharma and Reddy, 2004).

垃圾填埋场最常见的最终用途是开发用于娱乐用途的土地。娱乐用途的例子有高尔夫球场、自然公园、田野以及供公众使用的步行道或自行车道。这些类型的开发相对容易建造和维护,因为废物分解引起的差异沉降不会像对建筑物那样对娱乐设施产生不利影响。但是,结算仍然是一个必须考虑的问题。除了填埋场普遍存在的沉降和其他问题外,在任何娱乐最终用途设计中,封盖、树木和景观美化都是必须仔细设计和维护的关键特征(Sharma 和 Reddy,2004 年)。

Settlement 沉降

Sharma and Reddy (2004) suggest that for recreational end uses, the issue of differential settlement is more important than average settlement. Differential settlement can adversely affect grades throughout the site, which are designed to achieve consistent drainage/runoff, by changing the direction of drainage or by ponding. Ponding is one consequence of differential settlement that is easy to fix in a field or on a golf course simply by adding soil to to the affected area. More challenging to mitigate would be the reversal of a drainage path due to differential settlement. Because of this, a predicted settlement contour map for the site should be prepared and referenced in the implementation of the development. Differential settlement can also damage paved walkways and other permanent structures. To manage this, paths can be left unpaved until a sufficient amount of the total settlement has occurred.

Sharma 和 Reddy (2004) 认为,对于娱乐最终用途,差异沉降问题比平均沉降问题更重要。差异沉降会对整个场地的坡度产生不利影响,这些坡度旨在通过改变排水方向或积水来实现一致的排水/径流。积水是差异沉降的结果之一,很容易在田间或高尔夫球场上修复,只需在受影响的区域添加土壤即可。更具挑战性的缓解将是由于差异沉降导致的排水路径的逆转。正因为如此,在开发的实施中应该准备和参考该地点的预测沉降等高线图。差异沉降也会损坏铺砌的人行道和其他永久性结构。

Landfill Cap and Vegetation 垃圾填埋场盖帽和植被

Design and maintenance of the landfill cap is extremely important for recreational end uses because of the direct contact humans and animals have with the ground surface. This could require the landfill owner to use a deeper cover system than what is required by regulations. Additionally, in terms of design, unless the end use plan existed when the waste was placed, there may be costly excavation costs to remove and replace waste in some places, and to import and place fill to bring elevations and grades to where they are required for the design. The USEPA (2014) suggests that if burrowing animals could pose a danger to the geomembrane, a layer of stone/cobble should be placed over the geomembrane to prevent damage from burrowing. Similar considerations should be made if damage could be caused by root penetration. Sharma and Reddy suggest that trees be given at least 3 ½ feet of topsoil to accommodate their deeper root systems compared to grassy vegetation.

由于人类和动物与地面直接接触,垃圾填埋场盖的设计和维护对于最终娱乐用途极为重要。这可能要求垃圾填埋场所有者使用比法规要求更深的覆盖系统。此外,在设计方面,除非在放置废物时存在最终用途计划,否则可能需要昂贵的挖掘成本来清除和替换某些地方的废物,以及进口和放置填充物以将高程和坡度带到需要的地方为设计。USEPA (2014) 建议,如果穴居动物可能对土工膜造成危险,则应在土工膜上放置一层石头/鹅卵石,以防止穴居造成损坏。如果损坏可能是由根部穿透造成的,则应进行类似的考虑。

Nature parks or wildlife preserves are a common end use designed to promote native vegetative and animal species. According to the USEPA (2014), these designs typically try to minimize the need for mowing grass and using fertilizer, leading to cost savings. When attempting to stimulate a natural environment, sometimes invasive plant species or animals that stifle native growth must be removed. Another consideration is that cover soils often have low nutrient contents and unsatisfactory pH ranges (Sharma and Reddy, 2014). Because of this, wildlife must be chosen that can survive in this environment, or care must be taken to provide soils that are suitable for the intended growth.

自然公园或野生动物保护区是一种常见的最终用途,旨在促进本地植物和动物物种。根据 USEPA(2014 年),这些设计通常会尽量减少割草和使用化肥的需求,从而节省成本。当试图刺激自然环境时,有时必须去除抑制原生生长的入侵植物物种或动物。另一个考虑因素是覆盖土壤通常具有低营养成分和不令人满意的 pH 值范围(Sharma 和 Reddy,2014 年)。因此,必须选择能够在这种环境中生存的野生动物,或者必须注意提供适合预期生长的土壤。

Case Study – Key Largo Landfill

案例研究 – Key Largo 垃圾填埋场

A case study that highlights vegetation aspects of recreational landfill end uses comes from a set of case studies by Robert Mackey (1996). The Key Largo Landfill in Monroe County, Florida, is a landfill that was in operation between the 1970s and 1992, that became the site of a 15 acre wildlife preserve. The site is bordered on three sides by the Florida Crocodile Reserve; consequently, the site is of great concern to the US Fish and Wildlife Service (USFWS). The Florida Department of Environmental Protection required the property owners to cooperate with USFWS in developing a post-closure plan. Some actions taken included removing a species of feral cat from the preserve that was preying on an endangered species of rat native to the area, removing exotic and invasive plant species, and replanting a native shrub species, which is a food source for an endangered butterfly species.

一个突出休闲垃圾填埋场最终用途的植被方面的案例研究来自 Robert Mackey(1996 年)的一组案例研究。佛罗里达州门罗县的 Key Largo 垃圾填埋场是 1970 年代至 1992 年间运营的垃圾填埋场,成为 15 英亩野生动物保护区的所在地。该地点的三边与佛罗里达鳄鱼保护区接壤。因此,该网站引起了美国鱼类和野生动物管理局 (USFWS) 的极大关注。佛罗里达州环境保护部要求业主与 USFWS 合作制定关闭后计划。采取的一些行动包括从保护区中清除一种野猫,这种猫正在捕食该地区的濒临灭绝的老鼠物种,清除外来和入侵植物物种,并重新种植本地灌木物种.

LFG Control 垃圾填埋气控制

Another area of concern for landfills repurposed into recreational facilities is landfill gas. Proper control of LFG is important for both odor control and fire safety. Because methane gas is known to be explosive at critical concentrations, LFG protection systems require proper operation, monitoring, and maintenance (Law, 2007). In one case, Renaissance Park, a community recreation complex built on a closed landfill in Charlotte, North Carolina, has some recurring issues with LFG control that needed to be addressed. This site is quite large, covering about 375 acres of landfill footprint, and includes various sports fields and a golf course. The original design did not have a robust gas collection system, possibly, according to the the author of the report, because there are no buildings beneath which gas could collect. Therefore; it was thought that LFG would not pose a problem. However, the park has experienced periodic ground fire hazards caused by ignition of LFG through cracks in the ground surface, and in 1993, a woman caused an explosion by lighting a cigarette lighter near a soccer field. As a result of these hazards, open fires have been banned at the park, and other LFG mitigation techniques were implemented.

将垃圾填埋场改造成娱乐设施的另一个关注领域是垃圾填埋场气体。LFG 的适当控制对于气味控制和消防安全都很重要。由于已知甲烷气体在临界浓度下具有爆炸性,因此垃圾填埋气保护系统需要适当的操作、监控和维护(Law,2007 年)。在一个案例中,位于北卡罗来纳州夏洛特的一个封闭式垃圾填埋场上的社区休闲综合体文艺复兴公园(Renaissance Park)存在一些需要解决的垃圾填埋气控制问题。这个场地相当大,占地约 375 英亩的垃圾填埋场,包括各种运动场和一个高尔夫球场。据该报告的作者说,最初的设计没有强大的气体收集系统,可能是因为没有可以收集气体的建筑物。所以; 人们认为LFG不会造成问题。然而,公园经历了周期性的地面火灾危险,原因是填埋气通过地表裂缝点燃,1993 年,一名妇女在足球场附近点燃打火机引发爆炸。由于这些危险,公园已禁止明火,并实施了其他垃圾填埋气缓解技术。

Public Opinion 舆论

One more issue to consider that often arises in all public projects, including landfill end uses, is public opinion. An ongoing debate exists at Cesar Chavez Park in Berkeley, California (USEPA, 2014). This 90 acre park built over a closed landfill includes hiking trails, shoreline and wetland areas, a dog park, and a wildlife sanctuary. Here, there is a controversy surrounding the issue of burrowing animals potentially causing damage to the liner system. Reportedly, the issue, which is typically mitigated by a layer of gravel above the geomembrane, has been amplified due to public feeding of the animals leading to an increased number of the animals. A solution has been suggested: trapping and removing the burrowing animals from the site, but activists have blocked that strategy from being implemented, citing a detrimental effect on Western Burrowing Owls that feed on the burrowing animals. As of the publication date of this report, new options were being explored to mitigate the danger to the liner while keeping balance of the native ecosystem intact.

在包括垃圾填埋场最终用途在内的所有公共项目中经常出现的另一个需要考虑的问题是公众舆论。加利福尼亚州伯克利的 Cesar Chavez 公园正在进行一场辩论(USEPA,2014 年)。这个占地 90 英亩的公园建在一个封闭的垃圾填埋场上,包括远足小径、海岸线和湿地区域、狗公园和野生动物保护区。在这里,关于穴居动物可能对班轮系统造成损害的问题存在争议。据报道,该问题通常通过土工膜上方的一层砾石来缓解,但由于动物的公共喂养导致动物数量增加,这一问题已被放大。提出了一个解决方案:将穴居动物从现场诱捕并移走,但活动人士阻止了该策略的实施,引用对以穴居动物为食的西部穴居猫头鹰的不利影响。截至本报告发布之日,正在探索新的选择,以减轻对班轮的危险,同时保持原生生态系统的平衡。

Structural Uses结构用途

In many cases, commercial or industrial buildings are constructed on closed landfills. There is great value in being able to repurpose the land for such uses, but any structure, including pavement, built atop a landfill has increased engineering problems associated with it, especially if the structure is large. Issues associated with structural improvements over closed landfills include settlement, management of LFG, and maintaining the integrity of the liner cap (USEPA, 2014).

在许多情况下,商业或工业建筑建在封闭的垃圾填埋场上。能够将土地重新用于此类用途具有很大的价值,但是在垃圾填埋场顶部建造的任何结构,包括人行道,都会增加与之相关的工程问题,尤其是在结构很大的情况下。与封闭式垃圾填埋场的结构改进相关的问题包括沉降、垃圾填埋气的管理以及保持衬垫盖的完整性(美国环保署,2014 年)。

The cover system is critical to protecting public health and the environment; thus, it is prohibited to penetrate the geomembrane during construction (Although there are cases where developers have been able to successfully use pile foundations). Additional fill soil is sometimes added on top of the cover layer to increase the area over which the building load affects the cover, leading to a more even stress distribution. To protect the building from accumulation of LFG, it is common practice to add a venting layer beneath the building. This system consists of a geomembrane directly beneath the building slab and 12 inches of gravel beneath the geomembrane. Sometimes, there are also perforated pipes to help vent the gas away from the building via active or passive LFG control systems.

保险制度对于保护公众健康和环境至关重要;因此,在施工过程中禁止穿透土工膜(尽管有开发商能够成功使用桩基的案例)。有时会在覆盖层顶部添加额外的填土,以增加建筑荷载影响覆盖层的面积,从而实现更均匀的应力分布。为了保护建筑物免受垃圾填埋气的堆积,通常的做法是在建筑物下方添加一个通风层。该系统由建筑板正下方的土工膜和土工膜下方 12 英寸的砾石组成。有时,还有穿孔管道通过主动或被动 LFG 控制系统帮助将气体从建筑物中排出。

Possibly the most difficult issue to deal with in terms of structures over landfills is settlement. Calculation of settlement of MSW layers has some similarities with settlement of soil materials, but the highly variable and anisotropic nature of waste materials, along with their tendency to degrade over time, causes the estimation to be much more complicated than for a soil. For a review of settlement calculation, refer to the proceeding section on settlement of waste layers.

就垃圾填埋场的结构而言,最难处理的问题可能是沉降。MSW 层沉降的计算与土壤材料的沉降有一些相似之处,但废物的高度可变性和各向异性,以及它们随时间降解的趋势,导致估计比土壤复杂得多。有关沉降计算的回顾,请参阅前面关于废物层沉降的部分。

Case studies of commercial developments on closed landfills tend to have unique aspects to each project. The Lakeside Marketplace landfill redevelopment is a shopping center in Acworth, Georgia, where prior to development, an underground fire had occured due to LFG combustion (Law, 2007). Target Corporation, with the intent to build a SuperTarget store on the land, paid to have the subsurface fire mitigated and upgrade the gas control systems. Buildings at the Lakeside Marketplace were constructed with the typical geomembrane and gravel layer beneath each building, with passive LFG control venting out the gas. Dynamic deep compaction was used in high traffic areas and in areas where the building footprint was shallow to stabilize the ground. To combat settlement, other areas of the buildings were supported either by 60 foot H-piles or aggregate piers.

封闭式垃圾填埋场的商业开发案例研究往往对每个项目都有独特的方面。Lakeside Marketplace 垃圾填埋场重建项目是乔治亚州 Acworth 的一个购物中心,在开发之前,由于 LFG 燃烧而发生了地下火灾(Law,2007 年)。Target 公司打算在陆地上建立一家 SuperTarget 商店,并支付了费用以减轻地下火灾并升级气体控制系统。Lakeside Marketplace 的建筑物是在每栋建筑物下方使用典型的土工膜和砾石层建造的,被动 LFG 控制排放气体。动态深度压实用于人流量大的区域和建筑物占地面积较浅的区域以稳定地面。

A unique solution to deal with settlement was implemented at the Colma Landfill Home Depot, a well-known case study in commercial landfill end-use development (Law, 2007) due to the unique and creative solutions implemented in the design. Because there was a large amount of expected differential settlement, the designers came up with an idea for a “floating slab” which has a hinge type connection at the building-parking lot interface. This connection allows for differential settlement to occur without inducing a cracking moment in the slab. It is also possible to jack up the slab from beneath to raise the grade. Additionally, flexible connections were used for the utilities to allow for differential settlement. Figures 1 and 2 illustrate the hinged slab and flexible utility connections. The building is supported by 150-foot H-piles. According to the USEPA (2014), the deep piles were able to be used because the landfill did not have a geomembrane liner to penetrate, as it was an old landfill built before modern regulations took place. To control LFG, active collection and removal systems were used to remove the gas before it could reach the building.

Colma 垃圾填埋场 Home Depot 实施了一种独特的解决解决方案,这是商业垃圾填埋场最终用途开发(Law,2007 年)的一个著名案例研究,因为设计中实施了独特和创造性的解决方案。由于预计会有大量的差异沉降,设计师想出了一个“浮板”的想法,它在建筑物-停车场接口处具有铰链式连接。这种连接允许在不引起板坯开裂力矩的情况下发生不均匀沉降。也可以从下面顶起板来提高坡度。此外,公用设施使用了灵活的连接,以允许差异沉降。图 1 和图 2 显示了铰接板和柔性公用设施连接。该建筑由 150 英尺的 H 桩支撑。根据美国环保局(2014)的说法,之所以能够使用深桩,是因为垃圾填埋场没有土工膜衬垫可以穿透,因为它是在现代法规出台之前建造的旧垃圾填埋场。为了控制 LFG,使用主动收集和清除系统在气体到达建筑物之前将其清除。

Figure 1: Hinged slab connection (Law, 2007)

图 1:铰接板连接(法律,2007 年)

Figure 2: Flexible utility connection (Law, 2007)

图 2:灵活的公用设施连接(法律,2007 年)

Settlement of Waste Layers废物层的沉降

For any landfill end-use, but especially for end-uses including construction of buildings, it is critical to estimate as accurately as possible the settlement in a waste layer. Settlement of waste layers occurs due to primary consolidation, secondary consolidation, biodegradation of waste, and residual settlement. Many researchers have developed models for this, but most models are based off, or are calibrated versions of, the 1973 Sowers method. Sowers method is based off consolidation theory and resembles the traditional e-log p method. In Sowers’ method, primary settlement in a waste layer is calculated from the equation 1.

对于任何垃圾填埋场的最终用途,尤其是最终用途,包括建筑物的建造,尽可能准确地估计废物层中的沉降是至关重要的。废物层的沉降是由于初级固结、二次固结、废物的生物降解和残余沉降而发生的。许多研究人员为此开发了模型,但大多数模型都基于 1973 年的 Sowers 方法,或者是经过校准的版本。Sowers 方法基于整合理论,类似于传统的 e-log p 方法。在 Sowers 的方法中,废物层中的初级沉降由等式 1 计算得出。

In this expression, S is the primary settlement in the waste layer, H is the initial thickness of the layer, Cc is the primary compression index, e0 is the initial void ratio of the waste, P0 is the initial vertical stress at the middle of the layer, and ∆P is the increase in vertical stress at the middle of the layer. The total primary settlement would then be the summation of primary settlements of each layer of waste considered. According to Sharma and Reddy (2004), the primary settlement is expected to occur within one to four months of loading.

式中,S 为弃土层的初次沉降,H 为弃土层的初始厚度,C c为初次压缩指数,e 0为弃土的初始空隙率,P 0为初始竖向应力层中部,ΔP 是层中部垂直应力的增量。然后,总的初级沉降将是所考虑的每一层废物的初级沉降的总和。根据 Sharma 和 Reddy (2004) 的说法,初步沉降预计将在装载后的一到四个月内发生。

由废物自重引起的废物层二次沉降由公式 2 给出。

The secondary settlement of a waste layer due to the self-weight of the waste is given by equation 2.

In Eq. 2, ∆HSW is the secondary settlement due to the self-weight of waste, Cα(SW) is the coefficient of secondary compression due to self-weight, t1 is the length of time for primary consolidation to take place, and t2 is the amount of time passed since the placement of the waste. Secondary settlement due to external loads occurs at a different rate than that from self-weight, indicated in Equation 3, where Cα(EL)is the coefficient of secondary compression due to an external load.

在等式。2、ΔH SW为垃圾自重二次沉降,C α(SW)为自重二次压缩系数,t 1为一次固结发生的时间, t 2是自放置废物以来经过的时间量。由外部载荷引起的二次沉降发生率与自重不同,如公式 3 所示,其中 C α(EL)是由外部载荷引起的二次压缩系数。

Therefore, the total settlement is given by equation 4.

因此,总沉降由等式 4 给出。

At long time periods, the secondary settlement of waste layers starts to become very large compared to soil materials. This model is not perfect because even if the designer calibrates the model to their site, it does not account for the waste degradation in the correct way. However, the model gives a good enough estimate that it continues to be used today.


Although Sowers’ method is the most well-known model for MSW settlement, other models have been proposed in attempts to more accurately reflect the degradation behavior of the waste. For example, Chen and Chen (2011) developed a numerical model to solve a differential equation that includes effects of pore gas diffusion gradients and biodegradation models. The model is calibrated to calculate the accumulation of gas in the waste layer with time along with the transportation of the gas out of the system that leads to settlement under the weight of the waste. This model has been validated against field data as shown in Figure 3.

尽管 Sowers 的方法是最知名的 MSW 沉降模型,但也有人提出了其他模型,试图更准确地反映废物的降解行为。例如,Chen 和 Chen (2011) 开发了一个数值模型来求解一个微分方程,其中包括孔隙气体扩散梯度和生物降解模型的影响。该模型经过校准,可计算废物层中气体随时间的积累以及气体从系统中运出导致在废物重量下沉降的情况。该模型已针对现场数据进行了验证,如图 3 所示。

Figure 3: Simulation results of the Mission Canyon landfill settlement (Chen and Chen, 2011).

图 3: Mission Canyon 垃圾填埋场的模拟结果(Chen 和 Chen,2011 年)。

There are several methods available to attempt to reduce secondary compression settlement. Sharma and Reddy suggest dynamic compaction, grouting, or surcharge loading. However, according to Coduto et al. (2016), dynamic compaction typically has an effective zone of about 15 to 30 feet. Therefore, for deep landfills, this method would not have the range to densify all of the waste material. Coduto also claims that due to the large impact forces of dynamic tamping, shock waves can be damaging to nearby existing structures. Therefore, great care should be taken to protect important landfill systems such as the gas and leachate collection systems, and geomembranes. Grouting could theoretically be a good way to fill voids left by decomposed waste and by adding stiffness to the material, thereby reducing secondary settlement. This would probably need to be done before placement of geomembranes to avoid penetration during the grouting process. Perhaps the easiest way to reduce secondary settlement would be by surcharge loading. According to Coduto, surcharge loading requires years in order to be effective, but in the case of a landfill, time may not be an issue. When filling the landfill, the owners will probably have a stockpile of soil for daily cover on site—that can be a cheap source of surcharge load that requires no expertise to implement. Additionally, development doesn’t always take place directly after closure of the landfill, so there may be some downtime during which surcharging is a simple and cheap option. If surcharging is implemented, the Sowers method could easily be modified to include a recompression term for the waste. Again, it is best to use site-specific data to determine the coefficients of compression.

有几种方法可用于尝试减少二次压缩沉降。Sharma 和 Reddy 建议使用动态压实、灌浆或超载加载。然而,根据 Coduto 等人的说法。(2016),动态压实通常具有约 15 至 30 英尺的有效区域。因此,对于深层垃圾填埋场,这种方法无法使所有废料致密化。Coduto 还声称,由于动态夯实的巨大冲击力,冲击波可能会损坏附近的现有结构。因此,应特别注意保护重要的垃圾填埋系统,例如气体和渗滤液收集系统以及土工膜。从理论上讲,灌浆可能是填充分解废物留下的空隙并增加材料刚度的好方法,从而减少二次沉降。这可能需要在放置土工膜之前完成,以避免在灌浆过程中渗透。也许减少二次沉降的最简单方法是通过超载。根据 Coduto 的说法,附加费装载需要数年才能有效,但在垃圾填埋场的情况下,时间可能不是问题。在填埋填埋场时,业主可能会在现场储存用于日常覆盖的土壤——这可能是一种廉价的附加费来源,无需专业知识即可实施。此外,开发并不总是在垃圾填埋场关闭后直接进行,因此可能会有一些停机时间,在此期间,附加费是一种简单且便宜的选择。如果实施超载,Sowers 方法可以很容易地修改为包括废物的再压缩项。

Energy Production from Landfill Gas


Landfill gas (LFG) produced from the biodegradation of organic waste is a major consideration that all landfills must account for during operational years and for many years after closure. The time period of LFG production can be lengthened if biodegradation rates are low, as is often the case due to the moisture-limited environment of a landfill. Landfill gas can be produced for up to 50 years after landfill closure (USEPA, 2005), thus a long-term plan for gas collection and control must be generated and adhered to. Since LFG can contain mercury, VOCs, and other HAPs, there is a great risk to humans and wildlife if the gas is inhaled (USEPA, 2005). Another hazard is the possibility of explosion if LFG is allowed to build up without proper ventilation. Whether or not the landfill is slated for a post-closure development, LFG must be able to vacate the landfill.

有机废物生物降解产生的垃圾填埋气 (LFG) 是所有垃圾填埋场在运营期间和关闭后多年内必须考虑的主要考虑因素。如果生物降解率低,填埋气生产的时间可以延长,这通常是由于垃圾填埋场的湿度限制环境。垃圾填埋场关闭后,垃圾填埋场的气体可产生长达 50 年(美国环保局,2005 年),因此必须制定并遵守气体收集和控制的长期计划。由于垃圾填埋气可能含有汞、挥发性有机化合物和其他 HAP,如果吸入气体,人类和野生动物将面临巨大风险(美国环保署,2005 年)。如果在没有适当通风的情况下允许 LFG 堆积,另一个危险是可能发生爆炸。无论垃圾填埋场是否计划在关闭后进行开发.

Typically, LFG is composed of half methane and half carbon dioxide, with trace amounts of other gases present. This methane can be harnessed and burned to produce electricity. Landfills that do not capture LFG for use as a power source either burn LFG with a flare or emmit it into the atmosphere. Since the passing of RCRA, direct release to the environment is no longer a practical option for new landfills in the United States (Bogner, 1990).

通常,LFG 由一半的甲烷和一半的二氧化碳组成,并含有微量的其他气体。这种甲烷可以被利用和燃烧来发电。不收集垃圾填埋气用作能源的垃圾填埋场要么用火炬燃烧垃圾填埋气,要么将其排放到大气中。自从 RCRA 通过以来,直接排放到环境中不再是美国新填埋场的实际选择(Bogner,1990 年)。

While all landfills will produce some amount of LFG, it is important to determine the anticipated composition of the waste for the landfill to determine if enough methane will be produced to be a feasible energy source. Certain landfills will not degrade enough material to produce economical quantities of methane. For example, landfills that are used to dispose of any kind of ash (incinerator, coal plant, etc.) will not be ideal candidates for LFG utilization (Bogner, 1990). However, landfills that take in a large quantity of wastewater treatment sludge are great candidates for LFG utilization, as the wastewater introduces high amounts of moisture and nutrients. As always, regardless of whether LFG will be harnessed as an energy source, the gas must be controlled and handled as required by legislation.

虽然所有垃圾填埋场都会产生一定量的 LFG,但重要的是确定垃圾填埋场的预期废物成分,以确定是否会产生足够的甲烷作为可行的能源。某些垃圾填埋场不会降解足够的材料来产生经济数量的甲烷。例如,用于处理任何类型灰烬的垃圾填埋场(焚化炉、燃煤厂等)都不是 LFG 使用的理想选择(Bogner,1990 年)。然而,吸收大量废水处理污泥的垃圾填埋场是垃圾填埋气利用的理想选择,因为废水会引入大量的水分和营养物质。与往常一样,无论垃圾填埋气是否被用作能源,都必须按照立法要求对气体进行控制和处理。

Landfill gas is generally collected and routed out of landfills through a passive or active system of wells and connector pipes. In a passive system, the wells are open to the atmosphere, and either escape directly (as in old/outdated systems) or are burned by flare before exiting. Passive systems are cheaper to operate and maintain, but in a large or topographically-challenging landfill, or in any system planning to use LFG as an energy source, an active system is necessary. Active systems operate the wells under vacuum or pressurized conditions to move LFG. These systems are always necessary when using LFG as an energy source, as the components work most efficiently when operated under steady state conditions (USEPA, 2005), which are easier to produce with the control offered by active systems. The design of the landfill collection system is dependent on each specific landfill site, with important factors being the composition of the waste and moisture conditions at specific locations (Xue et al, 2013). A typical gas collection well is shown in Figure 4.

垃圾填埋气通常通过井和连接管的被动或主动系统收集并排出垃圾填埋场。在被动系统中,油井对大气开放,要么直接逃逸(如在旧/过时的系统中),要么在退出前被火炬燃烧。无源系统的运行和维护成本更低,但在大型或地形复杂的垃圾填埋场,或任何计划使用垃圾填埋气作为能源的系统中,有源系统是必要的。主动系统在真空或加压条件下操作井以移动 LFG。当使用 LFG 作为能源时,这些系统始终是必需的,因为这些组件在稳态条件下运行时工作效率最高(USEPA,2005),通过主动系统提供的控制更容易生产。垃圾填埋收集系统的设计取决于每个特定的垃圾填埋场,重要因素是特定位置的废物组成和水分条件(Xue 等,2013)。典型的集气井如图 4 所示。

Figure 4: Typical gas collection well (USEPA, 2005)

图 4 : 典型的集气井 (USEPA, 2005)

There are three typical methods of using landfill gas for energy production: direct use in a gas fired furnace or boiler for heat generation, on-site electricity generation via an internal combustion engine or turbine, and production of natural gas through removal of other trace gases and CO2 (Bogner, 1990). The third method is an emerging technology; the first two methods comprise almost all of the current LFG use (USEPA, 2017).  Using LFG to generate heat or electricity both require combustion of the LFG gas and require a few special considerations. Untreated LFG can be used directly on site, but not transported as the amount of moisture in the gas is unfavorable (Ham, 1979). Thus, it is not uncommon to dehydrate the gas to acceptable moisture levels, as this also promotes complete combustion.

使用垃圾填埋气进行能源生产的典型方法有三种:直接在燃气炉或锅炉中供热,通过内燃机或涡轮机现场发电,以及通过去除其他微量气体生产天然气和二氧化碳(博格纳,1990 年)。第三种方法是一种新兴技术;前两种方法几乎涵盖了当前所有填埋气的使用(USEPA,2017)。使用 LFG 来产生热量或电力都需要 LFG 气体的燃烧,并且需要一些特殊的考虑。未经处理的填埋气可以直接在现场使用,但不能运输,因为气体中的水分含量不利(Ham,1979 年)。因此,将气体脱水至可接受的水分水平并不少见,因为这也促进了完全燃烧。

Traces of hydrogen sulfide and chlorinated hydrocarbons create an acidic environment that can corrode components, and siloxanes can lead to harmful deposits inside the turbine or engine (Storey et al, 2014). Scrubbers to remove hydrogen sulfide have been successful: a landfill in Albany, NY implemented a power-generation unit that passed a liquid reagent through the gas to remove H2S (Hansen and Bruce, 1997). If the hydrogen sulfide concentrations are not extreme, a robust, stainless steel engine or turbine might be sufficient to mitigate corrosion.  However, almost any concentration of deposit-forming sulfur compounds and siloxanes will lead to a shortened lifespan of equipment, as these deposits build up and impair movement and proper combustion. For these reasons, it is typical for LFG to undergo further treatment to ensure longevity of the energy recovery system. Jet separation, a method that takes advantage of the difference in molecular weight of gases has been shown to be somewhat successful while proven methods of using carbon adsorption and refrigeration are still in use (Storey et al, 2014).

微量的硫化氢和氯化碳氢化合物会造成酸性环境,会腐蚀部件,而硅氧烷会导致涡轮机或发动机内部产生有害沉积物(Storey 等人,2014 年)。去除硫化氢的洗涤器取得了成功:纽约州奥尔巴尼的一个垃圾填埋场安装了一个发电装置,该装置将液体试剂通过气体去除 H2S(Hansen 和 Bruce,1997 年)。如果硫化氢浓度不是极端的,坚固的不锈钢发动机或涡轮机可能足以减轻腐蚀。然而,几乎任何浓度的形成沉积物的硫化合物和硅氧烷都会导致设备寿命缩短,因为这些沉积物会积聚并损害运动和正常燃烧。由于这些原因,垃圾填埋气通常会进行进一步处理,以确保能量回收系统的使用寿命。喷射分离是一种利用气体分子量差异的方法,已被证明在一定程度上取得了成功,而使用碳吸附和制冷的成熟方法仍在使用中(Storey 等人,2014 年)。

Renewable Energy Production- Solar and Wind


Solar 太阳能

In certain areas of the United States where sunshine is abundant, transforming a closed landfill into a solar farm is an enticing possibility. Examples of these solar farms have been produced in the city of Houston and at the Sarasota County Landfill in Florida (Prajnasmita Mohapatra, et al, 2012).

在美国某些阳光充足的地区,将封闭的垃圾填埋场改造成太阳能农场是一种诱人的可能性。这些太阳能农场的例子已经在休斯顿市和佛罗里达州的萨拉索塔县垃圾填埋场生产(Prajnasmita Mohapatra 等人,2012 年)。

Generally, there are two methods for converting solar energy to electricity. The method most commonly applied in the case of landfill end-uses is through the use of PV (photovoltaic) cells (Prajnasmita Mohapatra, et al, 2012).  Within the realm of photovoltaic cells, there are two PV technologies that have been used extensively in commercial solar applications; crystalline silicon and thin film (USEPA, 2013).  Silicon photovoltaic cells are the “traditional” solar panels; mounted on roofs or foundations that can either rotate or stay fixed.  Thin film PV cells are either made from silicon or other non-silicate materials (cadmium), but like the name implies, are very thin; only a few micrometers thick.  While crystalline silicon PV technology has a higher efficiency than thin film technology, thin film PV cells are so thin and flexible that they can be integrated into a landfill cover membrane (USEPA, 2013).  In either case, these panels are placed where they can receive sunlight, and then directly convert the sunlight into electricity.  When sunlight strikes a PV cell, the electrons within the layers of the PV cells begin to move from one layer to another, inducing an electric current (USEPA, 2013).  This current can then either be stored (in batteries or the grid), or used directly to power appliances.  The other method involves using a system of mirrors to heat liquid (water) to drive a turbine (Prajnasmita Mohapatra, et al, 2012).  A clever PV application at a landfill near San Antonio, Texas, incorporated thin film photovoltaic cells into the final membrane cover, decreasing the amount of construction necessary for the landfill to produce electricity.

通常,有两种将太阳能转化为电能的方法。在垃圾填埋场最终用途中最常用的方法是使用 PV(光伏)电池(Prajnasmita Mohapatra 等人,2012 年)。在光伏电池领域,有两种光伏技术已广泛用于商业太阳能应用;晶体硅和薄膜(美国环保署,2013 年)。硅光伏电池是“传统”太阳能电池板;安装在可以旋转或保持固定的屋顶或基础上。薄膜光伏电池由硅或其他非硅材料(镉)制成,但顾名思义,它们非常薄;只有几微米厚。虽然晶体硅光伏技术比薄膜技术具有更高的效率,薄膜光伏电池非常薄且灵活,可以集成到垃圾填埋场覆盖膜中(美国环保署,2013 年)。在任何一种情况下,这些面板都放置在可以接收阳光的地方,然后直接将阳光转化为电能。当阳光照射到光伏电池时,光伏电池层内的电子开始从一层移动到另一层,从而产生电流(美国环保署,2013 年)。然后可以存储该电流(在电池或电网中),或直接用于为电器供电。另一种方法涉及使用镜子系统加热液体(水)以驱动涡轮机(Prajnasmita Mohapatra 等人,2012 年)。在德克萨斯州圣安东尼奥附近的垃圾填埋场进行了一项巧妙的光伏应用,将薄膜光伏电池整合到最终的膜盖中.

Closed landfills are seemingly great locations to harvest solar energy because they have large amounts of open space with no tree cover, roads, access, and runoff plans already available.  However, the landfill site location must be evaluated to determine whether it receives enough sunshine to be economically viable. This is a function of the latitude, the region’s climate and (large-scale) topography, and the albedo of the earth (USEPA, 2013). Figure 5 shows a large-scale recommendation of the solar potential in the United States produced by NREL for use in an initial feasibility study and presented in USEPA, 2014.

封闭的垃圾填埋场似乎是收集太阳能的好地方,因为它们有大量的开放空间,没有树木覆盖、道路、通道和径流计划可用。但是,必须对垃圾填埋场的位置进行评估,以确定它是否接收到足够的阳光以在经济上可行。这是纬度、地区气候和(大尺度)地形以及地球反照率的函数(USEPA,2013)。图 5 显示了 NREL 提出的美国太阳能潜力的大规模建议,用于初步可行性研究,并在 2014 年提交给 USEPA。

Figure 5: Solar Energy Potential Map of United States

图 5:美国太阳能潜力图

Additionally, consideration must be made to whether the cover system can handle the PV system foundations, as well as the construction loads experienced during placement of solar cells (Prajnasmita Mohapatra, et al, 2012).  This consideration should ideally be considered in the initial design of the landfill, as solar panels are subjected to significant wind and snow loads in addition to gravity loads, depending on the climate and location. If the cover is able to withstand these loads, then the next consideration is topography. Landfills generally don’t have tremendously steep slopes, but solar panels perform best when oriented at the angle of incidence, the angle at which the panels are perpendicular to the ray of incoming sunlight (Prajnasmita Mohapatra, et al, 2012). The maximum potential is when the panels are perpendicular to the ray of the incoming sunlight. Thus, if the panels are on movable mounts, it is ideal to have them track the sun exactly. If the slope and foundation cannot support the solar panel at this angle, then the slope should be modified, or a different location should be chosen for the solar panels. This issue was mitigated at the San Antonio landfill by integrating the PV cells directly into the cover membrane. In this way, slope stability was not an issue.

此外,必须考虑覆盖系统是否可以处理光伏系统的基础,以及在放置太阳能电池期间所经历的施工负荷(Prajnasmita Mohapatra,等,2012)。理想情况下,应在垃圾填埋场的初始设计中考虑这一考虑,因为太阳能电池板除了重力载荷外,还要承受巨大的风雪载荷,具体取决于气候和位置。如果盖子能够承受这些负载,那么接下来要考虑的是地形。垃圾填埋场通常没有非常陡峭的斜坡,但太阳能电池板在以入射角定向时表现最佳,入射角是太阳能电池板垂直于入射太阳光线的角度(Prajnasmita Mohapatra,等,2012)。最大的潜力是当面板垂直于入射阳光的光线时。因此,如果面板安装在可移动的支架上,最好让它们精确地跟踪太阳。如果斜坡和地基不能以这个角度支撑太阳能电池板,则应修改斜坡,或为太阳能电池板选择不同的位置。通过将光伏电池直接集成到覆盖膜中,圣安东尼奥垃圾填埋场缓解了这个问题。这样,斜坡稳定性就不是问题了。通过将光伏电池直接集成到覆盖膜中,圣安东尼奥垃圾填埋场缓解了这个问题。这样,斜坡稳定性就不是问题了。通过将光伏电池直接集成到覆盖膜中,圣安东尼奥垃圾填埋场缓解了这个问题。这样,斜坡稳定性就不是问题了。

Wind Energy 风能

Similarly to solar power, wind energy can also be harnessed as a renewable energy source at a closed landfill site, but there are less documented cases of wind energy generation at these sites (USEPA, 2014). The economical advantage of producing wind power at a closed landfill site is heavily dependent on the amount of wind present at the site. NREL has also developed a wind resource map for use in a preliminary feasibility study, presented in Figure 6. Areas of concern when designing for wind energy production are settlement, bearing capacity, and liner integrity. Bearing capacity requires special consideration because of the large axial and lateral forces experienced by wind turbines, and the liner must be designed in a way that the turbine foundations do not compromise the liner.

与太阳能类似,风能也可以在封闭的垃圾填埋场用作可再生能源,但在这些填埋场进行风能发电的记录较少(美国环保署,2014 年)。在封闭的垃圾填埋场生产风力发电的经济优势在很大程度上取决于该场址的风量。NREL 还开发了用于初步可行性研究的风资源图,如图 6 所示。风能生产设计时关注的领域是沉降、承载能力和衬垫完整性。由于风力涡轮机承受较大的轴向力和侧向力,因此需要特别考虑承载能力,并且衬套的设计方式必须使涡轮机基础不会损害衬套。

Figure 6: Wind Energy Potential Map of United States

图 6:美国风能潜力图

Other Uses for Closed Landfills


Agriculture 农业

It is possible to use a closed landfill for agricultural use and appears to be an attractive option due to the large open area atop a landfill (USEPA, 2014). A major advantage of using a closed landfill for agricultural development is that structures causing excessive settlement and requiring foundations are not necessary. However, that does not mean that no special planning is involved. The grading and irrigation plan for the agricultural space must be compatible with the typical regulations regarding runoff and management of waste. If agriculture is the intended end use, it would be wise to integrate the designs, saving money from redesigning and grading later. Special concerns related to agricultural use are contamination of crops from landfill emissions, and protecting the cap from damage from agricultural activities. As with recreational end uses, this could mean adding thicker layers of topsoil to avoid root penetration and damage from machines. Although a properly managed landfill closure would ensure the integrity of the liner and avoid contamination anyway, several states have banned the use of the land for agriculture, while other states evaluate permittance of agricultural use on a case-by-case basis. Therefore, the landfill owner should consult state and local laws to determine if agriculture is a viable option.


Landfill Mining 垃圾填埋场采矿

Landfill mining has a wide variety in application and purpose. Burlakovs et al. (2017) discusses the state of landfill mining globally and discusses various reasons why landfill mining is applied. Figure 7 shows the distribution of types of landfill mining projects in Europe, USA, and Asia. Notably, resource reclamation is not typically the primary purpose for landfill mining except in Asia, being less popular than pollution reduction, recultivation of the site, and voidspace recovery in Europe and USA. Landfill mining can be a useful tool in reclaiming land to be used for other end uses described in this paper, but landfill mining itself is not the end use of the landfill. However, as is always the case, planning ahead for landfill mining will save money on redesigning and extra work down the road. Landfill owners can methodically group together waste materials that are expected to be worth reclaiming at a future time, reducing the cost of excavating and separating out the useful materials and increasing the quality of reclaimed materials. Overall, according to Krook (2012), landfill mining is a somewhat immature field that requires more research and experience to develop standard practices for operation. He also claims that much of the known information about landfill mining is owned by contractors experienced in landfill mining and is not based on research. Thus, more research should augment our current experience to further develop the field of landfill mining.

垃圾填埋采矿的应用和目的多种多样。Burlakovs 等人。(2017 年)讨论了全球垃圾填埋场采矿的状况,并讨论了应用垃圾填埋场采矿的各种原因。图 7 显示了欧洲、美国和亚洲垃圾填埋场采矿项目类型的分布。值得注意的是,除亚洲外,资源回收通常不是垃圾填埋场采矿的主要目的,在欧洲和美国不如减少污染、场地复垦和空隙空间回收那么受欢迎。垃圾填埋场开采可以是一种有用的工具,可以将土地用于本文所述的其他最终用途,但垃圾填埋场开采本身并不是垃圾填埋场的最终用途。然而,与往常一样,提前规划垃圾填埋场采矿将节省重新设计和未来额外工作的资金。垃圾填埋场所有者可以有条不紊地将预计将来值得回收的废物组合在一起,从而降低挖掘和分离有用材料的成本并提高回收材料的质量。总体而言,根据 Krook (2012) 的说法,垃圾填埋场采矿是一个有点不成熟的领域,需要更多的研究和经验来制定标准的操作实践。他还声称,关于垃圾填埋场采矿的许多已知信息都由在垃圾填埋场采矿经验丰富的承包商所有,而不是基于研究。因此,更多的研究应该增加我们目前的经验,以进一步发展垃圾填埋场采矿领域。降低挖掘和分离有用材料的成本,提高回收材料的质量。总体而言,根据 Krook (2012) 的说法,垃圾填埋场采矿是一个有点不成熟的领域,需要更多的研究和经验来制定标准的操作实践。他还声称,关于垃圾填埋场采矿的许多已知信息都由在垃圾填埋场采矿经验丰富的承包商所有,而不是基于研究。因此,更多的研究应该增加我们目前的经验,以进一步发展垃圾填埋场采矿领域。降低挖掘和分离有用材料的成本,提高回收材料的质量。总体而言,根据 Krook (2012) 的说法,垃圾填埋场采矿是一个有点不成熟的领域,需要更多的研究和经验来制定标准的操作实践。他还声称,关于垃圾填埋场采矿的许多已知信息都由在垃圾填埋场采矿经验丰富的承包商所有,而不是基于研究。因此,更多的研究应该增加我们目前的经验,以进一步发展垃圾填埋场采矿领域。他还声称,关于垃圾填埋场采矿的许多已知信息都由在垃圾填埋场采矿经验丰富的承包商所有,而不是基于研究。因此,更多的研究应该增加我们目前的经验,以进一步发展垃圾填埋场采矿领域。他还声称,关于垃圾填埋场采矿的许多已知信息都由在垃圾填埋场采矿经验丰富的承包商所有,而不是基于研究。因此,更多的研究应该增加我们目前的经验,以进一步发展垃圾填埋场采矿领域。

Figure 7: Purpose for landfill mining projects in Europe, North America, and Asia (Kurlakovs et al., 2017)

图 7:欧洲、北美和亚洲垃圾填埋场采矿项目的目的(Kurlakovs 等人,2017 年)


Many possibilities exist for post-closure landfill development. The large, open tract of land is amenable to many end-uses, the most popular of which include recreation, solar farms, and landfill gas usage. Less commonly, but which increasing frequency are structural/commercial developments. It is beneficial to the landowner to plan as far ahead of time as possible for the intended end use, if possible, to save time and money on design and development. Many factors discussed in this paper will help determine the appropriateness of alternatives for landfill end-use. However, all landfill site are unique in some way and will require judgement by engineers, governing bodies, and the public. As more landfills close, we will continue to see new and creative solutions to engineering problems on these sites.


End Uses of Landfills (垃圾填埋场的最终用途)