Evaluation of a peat filtration system for treating highway runoff in a karst setting

The deleterious character of highway runoff, especially following long periods without precipitation, has been well documented in the literature. It transports hydrocarbons, heavy metals, and other contaminants from highways, contributing to the pollution of surface water and groundwater. Groundwater is particularly vulnerable in karst areas where highway runoff is transferred quickly into subsurface conduit networks through open sinkholes and/or sinking streams. The difficulties in remediating contaminated karst aquifers make it crucial for karst aquifers to receive only uncontaminated water. A peat filtration system was constructed at the I-40/I-640 interchange in eastern Knoxville, Tennessee, USA, to remove highway runoff contaminants prior to being transported into karst aquifers. Recent field tests indicate that the system can significantly decrease the concentrations of analyzed constituents including PAHs (polyaromatic hydrocarbons), copper, and zinc. However, the removal efficiency depends on the concentration of the contaminants in the runoff. Long-term monitoring is required to determine the true effectiveness of the designed filtration system and its reliability.     

Mise-a-la-masse method,tracer tests and cave detection analysis of underground-river karst-conduit distribution and structure: a case study of the Dafengdong conduits in Guizhou Province,China

In karst areas, groundwater movement is dominated by conduit flow; thus, understanding the distribution and structure of karst conduits has great significance for water research, groundwater protection and engineering construction. With the Dafengdong (Guizhou Province, China) underground river karst as an example, a mise-a-la-masse method, tracer tests and cave detection were conducted to study the distribution and structure of karst conduits. Combined with information on the geological and hydrogeological conditions, the geological factors that form karst conduits were determined. It can be concluded that: (1) Under the influence of faults, karst conduits usually develop towards or along faults; (2) multiple karst conduits form easily on both sides of tectonic fracture zones; (3) both lithology and geological structure affect the formation of blue holes, and when the directions of karst conduits change, blue holes easily form in weak parts of the structure; (4) at springs where two aquifers intersect, with strong chemical dissolution of the lower karst aquifer and mechanical collapse of the upper aquifer, blue holes also form easily; and (5) integrated mise-a-la-masse method, tracer tests and cave detection can accurately discern the distribution and structure of karst conduits. Geological factors can be used to preliminarily delineate the distribution and structure of karst conduits in similar areas based on hydrogeological conditions. Such methods hold great significance for groundwater extraction and protection and engineering construction in karst areas.

     

基于钻孔抽水试验和示踪试验的岩溶地区含水层结构研究

岩溶含水层具有强异质性和各向异性特征,其空间结构的调查和认识是地下水流动和污染物迁移研究的重要基础。然而,岩溶含水层特殊的地质结构导致岩溶区水文地质调查非常困难。为了更好地掌握研究区岩溶含水层结构特征,本文在进行抽水试验的同时开展多示踪剂（荧光素钠、罗丹明、荧光增白剂）示踪试验。利用Theis标准曲线对比法分析抽水试验数据,计算试验场地渗透张量,根据示踪试验结果分析含水层结构性质。计算出研究区渗透张量主方向的导水系数分别为:0.297 m2·h-1和0.028 m2·h-1,给水度为1.19E-04,优势方向为东偏南18.47°。抽水条件下示踪试验获得3种示踪剂的回收率分别为:荧光素钠97.98%,罗丹明B47.34%,荧光增白剂39.54%;平均流速分别为:0.378 m·h-1、0.3 m·h-1和0.14 m·h-1,反映研究区岩溶孔隙、裂隙较小,示踪剂运移慢、时间长。荧光素钠和荧光增白剂的BTC曲线表现为单峰型,罗丹明B的BTC曲线表现为多峰型,表明研究区既发育优势流裂隙,又发育相对均匀裂隙。同时,示踪剂最大回收率方向与抽水实验所得渗透张量主方向相符。研究结果为岩溶含水层精细结构的刻画,水文模型物理参数的确定提供了方法和依据。      

Permeability of Municipal Solid Waste in Bioreactor Landfill with Degradation

Bioreactor landfills are operated for rapid stabilization of waste, increased landfill gas generation for cost-effective energy recovery, gain in landfill space, enhanced leachate treatment, and reduced post closure maintenance period. The fundamental process of waste stabilization in bioreactor landfill is recirculation of generated leachate back into the landfills. This creates a favorable environment for rapid microbial decomposition of the biodegradable solid waste. In order to better estimate the generated leachate and design of leachate recirculation system, clear understanding of the permeability of the Municipal Solid Waste (MSW) with degradation and the factors influencing the permeability is necessary. The objective of the paper is to determine the changes in hydraulic properties of MSW in bioreactor landfill with time and decomposition. Four small-scale bioreactor landfills were built in laboratory and samples were prepared to represent each phase of decomposition. Then, the changes in hydraulic properties of MSW in bioreactor landfill with time and decomposition were determined. A series of constant head permeability tests were performed on the samples generated in laboratory scale bioreactor landfills to determine variation of permeability of MSW with degradation. The test results indicated that the permeability of MSW in bioreactor landfills decreases with decomposition. Based on the test results, the permeability of MSW at the first phase of degradation was estimated as 0.0088 cm/s at density 700 kg/m³. However, with degradation, permeability decreased to 0.0013 cm/s at the same density, for MSW at Phase IV.     

Application of water quality control charts to spring monitoring in karst terranes

Presence of springs in karst terranes provides a unique opportunity to study the rather complex, multi-porosity, and multi-permeability system. When springs are used to evaluate the integrity of storage facilities for hazardous materials or waste disposal facilities constructed in karst areas, the spatial heterogeneity of karst aquifers makes intra-spring comparisons preferred statistical tests. One of the commonly used statistical tests is water quality control procedure such as Shewhart-CUSUM control charts. Appropriate application of the water quality control procedure to intra-spring monitoring depends on whether the assumptions can be justified about the aquifer that drains to the spring and the dataset collected at the spring. Violation of the assumptions would render the statistical tests invalid, which may result in a failure of the groundwater monitoring program. In intra-spring monitoring, it is the temporal variations of water quality at a karst spring need to be addressed, whereas the water quality at the spring is closely associated with the characteristics of the aquifer. The example datasets presented in the paper indicate that both false negative and false positive detections can occur if the temporal variation is not well characterized.     

Groundwater vulnerability assessment of the Cork Harbour area,SW Ireland

In the Cork Harbour area of SW Ireland, high yield karst and intergranular gravel aquifers are extremely vulnerable to pollution from a variety of sources, mainly due to the limited protection afforded by the thin cover of low permeability glacial and alluvial overburden. The main potential sources of pollution are due to rapid urbanisation of the Cork city area and its attendant infrastructure, and increased industrialisation in the area, with numerous new industries, particularly pharmaceutical and chemical industries, located around Cork Harbour. Other potential sources of pollution are a number of landfills in the area and an oil refinery near the mouth of Cork Harbour. Traditional agricultural sources of pollution also exist, due to increased use of chemical fertilisers. Finally, the susceptibility to saline intrusion of the karst and gravel aquifers around Cork Harbour is high due to the long coastline of the harbour and the low-lying nature of the karst synclines with their superimposed buried valleys.     

Groundwater monitoring for cement kiln dust disposal units in karst aquifers

Well-developed karst aquifers tend to be heterogeneous and consist of variable porosities. Groundwater monitoring and the associated data interpretations in such aquifers are often more complicated than porous medium aquifers. Collection of representative data in karst aquifers often requires monitoring at appropriately located wells and/or springs that are proven to connect to the groundwater system. Water samples are to be collected under different flow conditions, including base flow, high-flow, and low-flow. The sampling frequencies may vary from several months for base flows to minutes in response to recharge events. The groundwater monitoring program presented in this paper is for a cement kiln dust mono-fill site in a karst area of southern Indiana. Following dye tracing and extensive geophysical investigations, one spring was selected as a monitoring location. A second spring should be used as a monitoring location when the last cell of the mono-fill begins receiving the wastes. The paper discusses results from the first spring, at which nine background sampling events were completed to evaluate the natural variations of the water quality. Based on the background data, a statistical evaluation plan was developed for 12 water-quality parameters to determine the integrity of the landfill. The statistical power of the statistical analyses was evaluated by Monte Carlo simulations.     

Apparent Formation Factor for Leachate-Saturated Waste and Sediments: Examples from the USA and China

The formation factor relates bulk resistivity to pore fluid resistivity in porous materials. Understanding the formation factor is essential in using electrical and electromagnetic methods to monitor leachate accumulations and movements both within and around landfills. Specifically, the formation factor allows leachate resistivity, the degree of saturation, and, possibly, even the hydraulic conductivity of the waste to be estimated from non-invasive surface measurements. In this study, apparent formation factors are computed for three landfills with different types of waste as well as sediments contaminated by landfill leachate. Resistivity soundings at the closed Mallard North landfill in suburban Chicago (Illinois, USA) mapped leachate surfaces that were confirmed by monitoring wells. The resistivity of leachate-saturated waste from resistivity sounding inversions was then divided by the leachate resistivity values measured in-situ to compute apparent formation factors (Fa) ranging from 1.6 to 4.9. A global Fa of 3.0±1.9 was computed for the entire monitored portion of this landfill At a nearby mixed laboratory waste landfill, a 2D inverted resistivity section was used to compute an Fa of 2.9. Finally, a distinctly different Fa value of 10.6±2.8 was computed for leachate-saturated retorted oil and organic compounds. The Fa for aquifers containing contaminated groundwater fall in the same range as aquifers with normal groundwater, 1.7-3.9. However, models from inverted sounding curves over these contaminated areas exhibit unusually low resistivity layers, which may be diagnostic of contamination.     

Inference of the structure of karst conduits using quantitative tracer tests and geological information: example of the Swiss Jura

Karst aquifers are known for being particularly heterogeneous with highly transmissive conduits embedded in low permeability volumes of rock matrix. Artificial tracer experiments have been carried out in a complex karst aquifer of the folded Jura Mountains in Switzerland with the aim of deciphering the conduit organisation. It is shown that tracer experiments with multiple injection points under different flow conditions can lead to useful information on the conduits’ structure. This information has been combined with data from structural geology, spring hydrology, and speleological observations. A conceptual model of the conduit network shows that a detailed inference of the conduit organisation can be reached: geology controls conduit location and orientation; spring hydrology, including temporary springs, constrains conduit elevations and relative hydraulic heads in the aquifer subsystems; and tracer tests identify major flow paths and outlets of the system and dilution caused by non-traced tributaries, as well as the presence of secondary flow routes. This understanding of the Aubonne aquifer structure has important implications for the future management of the groundwater resource. Similar approaches coupling geological information, spring hydrology, and multi-tracer tests under various flow conditions may help to characterise the structure of the conduit network in karst aquifers.     

A new quantitative interpretation of the long-tail and plateau-like breakthrough curves from tracer tests in the artesian karst aquifer of Stuttgart, Germany

In 1998 and 1999, two multi-tracer experiments were conducted in the artesian karst aquifer of the mineral springs of Stuttgart, Germany. The breakthrough curves (BTCs) monitored at the springs showed very long tails or developed plateau-like concentration levels for more than 200 days. Initially, this observation was qualitatively explained by exchange between cavities with stagnant water and the active conduits. Since then, a new analytical solution for tracer transport in karst aquifers has become available, the “two-region non-equilibrium model” (2RNE), which assumes the presence of mobile and immobile fluid regions, and mass transfer between these two regions. The experiments were thus revisited, and it was possible to provide a more quantitative explanation of the observed behaviour. The new model simulated all BTCs very well, thus confirming the earlier qualitative explanation. The prolonged BTCs can be attributed to intermediate storage in cavities containing quasi-immobile groundwater, and slow release into active fractures and conduits. The results also demonstrate that karst aquifers are not always fast-flushing systems, but contaminants can sometimes remain in immobile fluid regions for long periods.     

Biogeochemistry of landfill leachate plumes

The literature has been critically reviewed in order to assess the attenuation processes governing contaminants in leachate affected aquifers. Attenuation here refers to dilution, sorption, ion exchange, precipitation, redox reactions and degradation processes. With respect to contaminants, focus is on dissolved organic matter, xenobiotic organic compounds, inorganic macrocomponents as anions and cations, and heavy metals. Laboratory as well as field investigations are included. This review is an up-date of an earlier comprehensive review. The review shows that most leachate contamination plumes are relatively narrow and do not in terms of width exceed the width of the landfill. The concept of redox zones being present in the plume has been confirmed by the reported composition of the leachate contaminated groundwater at several landfills and constitutes an important framework for understanding the behavior of the contaminants in the plume as the leachate migrates away from the landfill. Diverse microbial communities have been identified in leachate plumes and are believed to be responsible for the redox processes. Dissolved organic C in the leachate, although it appears to be only slowly degradable when the volatile organic acids are gone, apparently acts as substrate for the microbial redox processes. Several xenobiotic organic compounds have been found to be degradable in leachate contaminated groundwater, but degradation rates under anaerobic redox conditions have only been determined in a few cases. Apparently, observations in actual plumes indicate more extensive degradation than has been documented in the laboratory. The behavior of cations in leachate plumes is strongly influenced by exchange with the sediment, although the sediment often is very coarse and sandy. Ammonium seems to be subject to anaerobic oxidation, but the mechanisms are not yet understood. Heavy metals do not seem to constitute a significant pollution problem at landfills, partly because the heavy metal concentrations in the leachate often are low, and partly because of strong attenuation by sorption and precipitation. Although complexation of heavy metals with dissolved organic matter is significant, the heavy metals are in most cases still strongly attenuated in leachate-polluted aquifers. The information available on attenuation processes has increased dramatically during the last 15 a, but the number of well-documented full scale leachate plumes are still few and primarily from sandy aquifers. Thus, the diversity of attenuation processes in leachate plumes is probably not yet fully understood. Apparently, the attenuation processes in leachate plumes may for many contaminants provide significant natural remediation, limiting the effects of the leachate on the groundwater to an area usually not exceeding 1000 m from the landfill.     

KARSTIC: a sensitivity method for carbonate aquifers in karst terrain

. Groundwater in karstic aquifers can be dangerously sensitive to contamination. Many cities in the western USA rely on karstic carbonate aquifers for municipal water supplies. For example, Rapid City, South Dakota, pumps more than half of its drinking water from wells in the Madison Limestone. This work examined the sensitivity of karstic aquifers to surface contamination in mountainous terrain. Where karstic carbonate aquifers are exposed at their outcrop areas, they are particularly susceptible to the introduction of contamination through diffuse recharge or through point recharge at swallow holes along streams. Residential developments in mountainous regions of the western USA are encroaching on the recharge areas of karstic aquifers. Many of these residential developments are served by onsite wastewater disposal systems such as septic tanks and drain fields, with the attendant danger of introduction of pathogens from malfunctioning treatment systems above fractured limestone which offers little filtering. Where streams disappear into karstic aquifers at swallow holes, microbial contaminants such as Giardia or Cryptosporidium are a concern, as well as potential spills, leaks, or accidents along roads near these streams. The KARSTIC method developed and modified in this work puts greater emphasis on karst features than previous sensitivity procedures such as the US Environmental Protection Agency's DRASTIC method. The modified method gives increased attention to highly sensitive areas of karstic carbonate aquifers by weighting the synergistic effects of fracturing, karst development, and swallow holes of recharging streams. In a field application, hydrogeologic maps of a watershed in the Black Hills, USA, were digitized into a geographic information system. The resulting sensitivity map and report can be used by planners, managers, and the public as a screening tool for assessing groundwater sensitivity in regions which include karstic aquifers.     

Identification of buried sinkholes using refraction tomography at Ft. Campbell Army Airfield,Kentucky

Karst aquifers are highly susceptible to contamination, with numerous points of entry for contaminants through recharge features such as sinkholes, swallow holes and solutionally enlarged fractures. These recharge features may be filled or obscured at the surface, requiring the use of geophysical or remote sensing techniques for their identification. This study uses seismic refraction data collected at the Ft. Campbell Army Airfield (CAAF), Kentucky, USA, to test the hypothesis that refraction tomography is a useful tool for imaging bedrock depressions beneath thick overburden (greater than 20 m of unconsolidated sediment). Southeast of the main taxiway of CAAF seismic velocity tomograms imaged a bedrock low, possibly a closed depression, at a depth of 25 m that had been earlier identified through delay-time analysis of the same refraction data. Tomography suggests the bedrock low is about 250-m wide by 10-m deep at its widest point. High rates of contaminant vapor extraction over the western extension of this feature suggest a high concentration of contaminants above, and within, this filled bedrock low, the base of which may contain solutionally enlarged fractures (i.e. karst conduits) that could funnel these contaminants to the upper or lower bedrock aquifers. This study thus demonstrates the viability of seismic refraction tomography as a tool for identification of filled sinkholes and bedrock depressions in karst areas.     

Environmental impact and geochemical behavior of soil contaminants from an industrial waste landfill in Southern Brazil

Industrial waste landfills produce great impacts on soil and groundwater. There are many industrial waste landfills in Vale dos Sinos, Southern Brazil, which were inadequately planned and maintained since the industry started in the first half of the twentieth century. The largest industrial landfill in the Valley, which causes the most severe impacts on soil and groundwater, is the subject of this paper, which studies the environmental impacts and behavior of contaminants in soil. The landfill was carefully mapped on a scale of 1:1,000; 88 samples were collected from soil probes; the leachate of three samples was comprehensively analyzed; and soils mineralogy and chemistry were studied. Few studies have been made on this landfill. This study shows widespread contamination of soil in the surrounding areas of the landfill. Chromium, chloride and ammonium have the highest contamination levels, reflecting their high contents in landfill leachate. Contamination by petroleum hydrocarbons, cyanide and mercury is registered in more than 65% of soil samples with low concentrations. Lead, copper and barium show low contamination restricted to a few soil samples. Soil contamination occurs mainly in the unsaturated zone of the aquifer at the convergence points of stormwater, showing that the preferential transport of contaminants occurs on surface flow followed by soil infiltration. The results of leaching tests indicate high metal sorption capacity of soil. The remediation of contaminated soil must contain at least the following actions: sealing the top of the landfill, installation of geochemical barriers, removal of the liquid waste basins without sealing the base and collection and treatment of the rainwater drainage.     

典型岩溶包气带洞穴滴水水文过程研究——以桂林硝盐洞为例

选取桂林丫吉试验场硝盐洞为研究对象,通过示踪试验和高分辨率水文水化学监测,确定滴水补给来源,研究典型岩溶包气带洞穴滴水对降雨响应的水文过程。研究结果表明,硝盐洞XY5滴水主要受到两种径流成分补给,即集中补给的管道流和弥散流。硝盐洞上部包气带中可能存在表层岩溶带含水层,长期维持滴水流量。滴水流量、电导率和示踪剂浓度的峰值均出现在强降雨时段,表现出快速响应的管道流特征,存在降雨阈值引起硝盐洞滴水降雨响应。降雨前岩溶含水层水分条件是包气带水文响应差异的主要原因,雨季滴水对降雨响应迅速,XY5滴水对降雨响应的滞后时间为10 h;而旱季对降雨的响应滞后明显,滞后时间达9.8天,体现了土壤和表层岩溶带的调蓄作用。74.4 mm降雨量是旱季转雨季滴水响应的降雨阈值。借助于洞穴滴水的水文动态变化和示踪试验技术对于研究包气带水文过程,深入了解岩溶含水层结构及特征,揭示岩溶区降雨入渗补给机制具有重要作用。     

喀斯特洞穴体系元素迁移及环境指示研究进展

洞穴滴水与沉积物中的元素作为环境替代指标,在反映其物质来源以及反演古环境气候的研究中有着重要的作用,已受到国内外学者的广泛关注。本文在总结前人研究成果的基础上,概述了喀斯特洞穴体系中的元素迁移机理,重点对土壤、基岩、滴水中Ca、Mg、Sr、Ba四种元素的迁移变化机制进行了系统归纳;结合环境影响因素,分析了各元素的来源与特性,进而对滴水与沉积物中元素比值所反映的环境指示意义进行了综述。同时提出,应深入探究洞穴体系的元素迁移机制;结合洞穴环境体系的自身特点,区分元素指标在不同环境中的信息指示特征,提高沉积物中元素指示古气候环境信息的精准性;结合石漠化地表环境特征,从洞穴滴水的降雨响应研究入手,建立石漠化环境地下监测指标体系。      

Attenuation of landfill leachate at two uncontrolled landfills

Attenuation characteristics of landfill leachate were examined for two uncontrolled landfills in Korea. The two landfills containing municipal wastes without appropriate bottom liner and leachate treatment system have different landfill age, waste volume, and most importantly different hydrogeologic settings. One landfill (Cheonan landfill) is situated in an open flat area while the other (Wonju landfill) is located in a valley. Variations of various parameters including dissolved organic carbon (DOC), dissolved oxygen (DO), alkalinity, pH, electrical conductivity (EC), redox potential (ORP), ammonia (NH₃), nitrate (NO₃⁻), sulfate (SO₄²⁻), and chloride (Cl⁻) were examined along groundwater flow path. All these parameters were analyzed every month for a year. In the interior of the landfills, typical anaerobic conditions revealed by low DO and NO₃ concentrations, negative ORP values, high NH₃, alkalinity, and Cl⁻ concentrations were observed. Generally, higher levels of contaminants (DOC, NH₃, and Cl⁻) were detected in the dry season while they were greatly lowered in the wet season. Significantly, large decrease of Cl^- concentration in the wet season indicates that the dilution or mixing is one of dominant attenuation mechanisms of leachate. But detailed variation behaviors in the two landfills are different and they were largely dependent on permeability of surface and subsurface layers. The intermediately permeable surface of the landfills receives part of direct rainfall infiltration but most rainwater is lost to fast runoff. The practically impermeable surface of clayey silt (paddy field) at immediately adjacent to the Cheonan landfill boundary prevented direct rainwater infiltration and hence redox condition of the ground waters were largely affected by that of the upper landfill and the less permeable materials beneath the paddy fields prohibited dispersion of the landfill leachate into down gradient area. In the Wonju landfill, there are three different permeability divisions, the landfill region, the sandy open field and the paddy field. Roles of the landfill and paddy regions are very similar to those at the Cheonan. The very permeable sandy field receiving a large amount of rainwater infiltration plays a key role in controlling redox condition of the down gradient area and contaminant migration. This paper reports details of the attenuation and redox conditions of the landfill leachates at the two uncontrolled landfills.     

Karst terranes and environmental aspects

Karst is a complex geological phenomenon that relates to terranes composed of limestone, dolomites, gypsum, halite, or other soluble rocks. Protection of groundwater in karst against pollution is needed because of the high velocity of its flow (several hundreds of thousands of meters per day) and where polluted materials are carried without being filtered. Protection of karstic aquifers against pathogens and rapidly degradable chemicals is carried out for the catchment areas with an estimated delay time of 60 days and for a distance of more than 30 m. Tracer methods have recently become quite useful in karst regions; a tracer may respond as a multiimpulse because of different flow lines, flow velocities, and water aquifers. Therefore, if a total water balance has to be established, nearly all answer-back impulses should be considered.     

Test methods for characterizing contaminant transport in a glaciated carbonate aquifer

It is widely recognized that karstification can substantially influence flow and transport characteristics in carbonate aquifers. Surface features such as sinkholes are widely used to diagnose the presence of a karst aquifer, but specific borehole tests for karst have not been well defined. Such tests are especially important in glaciated areas where karst features have been eroded or buried by till. One such area is Smithville, Ontario, where more than 60 boreholes at a PCB-contaminated dolostone site provided an opportunity for a wide range of downhole tests and monitoring to be carried out. It was found that there were a number of useful tests for indicating karstification. These included (1) the order of magnitude differences between pump, slug and packer test results, (2) the presence of water table troughs, (3) rapid water level response following recharge events, (4) the rapid changes in water quality following recharge events, (5) water undersaturated with respect to calcite following recharge events, and (6) a wide range in fracture apertures along major bedding planes. Most parameters vary over a similar range at Smithville as they do at Mammoth Cave, Kentucky, indicating that the Smithville aquifer behaves as a typical karst aquifer.     

不同降雨模式下山谷型垃圾填埋场水分运移及其稳定性研究

近10年的运营经验表明,国内南方地区第1批建造的山谷型垃圾填埋场中的渗滤液水位一般较高。同时,现有研究表明,降雨入渗引起渗滤液水位过高是垃圾填埋场失稳的主要诱因之一。因此,研究强降雨条件下山谷型垃圾填埋场的水分运移规律及其稳定性,具有重要的现实意义。基于七子山填埋场浅层、中层和深层垃圾土的土-水特征曲线和Brooks-Corey公式,利用非线性拟合技术得到垃圾土的渗透性函数;运用饱和-非饱和渗流理论,对递减型、中心型、增强型和平均型4种降雨模式下七子山填埋场的水分运移进行了数值计算;利用极限平衡理论,对不同降雨模式下七子山填埋场的稳定性进行了分析。结果表明,降雨模式对山谷型垃圾填埋场内的水分运移规律和填埋场的稳定性有显著的影响,递减型降雨模式下填埋场内孔隙水压的变化最大,同时填埋场稳定系数也下降最为明显,为最不利降雨模式;经历7 d 746 mm的极端强降雨后,七子山填埋场具有极大的失稳隐患。