Average Rut Depth Research Articles

Analysis of the correlation between the pavement structure combinations and pavement performance using experimental sections

The new generation of pavement technology with the goal of longevity is an important supporting technology that can promote the achievement of sustainable development of high-speed roadways. To further investigate the evolution trend of long-life pavement performance, this paper paved experimental sections to explore the correlations between pavement structure combinations and pavement performances. This paper presented four experimental sections with different pavement structures, asphalt concrete layer thicknesses, and pavement materials. Then, this paper analyzed the effects of the seasonal factors, pavement structure, and lanes on the deflection value and rut depth from three dimensions by the Pearson correlation coefficient (PCC). Finally, this paper used the analysis of variance (ANOVA) to analyze the relationships between the layer thickness of various materials in the pavement structure and the pavement performances, including the deflection value, international roughness index (IRI), texture depth (TD), British Pendulum Number (BPN), sideway force coefficient (SFC), rut depth, and disease area. The results showed that the seasonal factors significantly affected the deflection values of pavement structures with PCCs of 0.61, 0.72, 0.53, and 0.78. The high temperatures increased the average deflection values by 22.85%, 72.88%, 77.61%, and 88.13%, respectively. Under the influence of high temperature in summer and traffic loads, the increased ranges of average rut depth were −0.2%, 4.89%, 9.56%, and 7.31%, respectively. The results of ANOVA showed that the pavement structure type and thickness of each structural layer significantly affected the deflection value, and there also was a strong correlation between the pavement structure type, thickness, BPN, and SFC with p-values less than 0.05. Increasing the thickness of the asphalt surface was beneficial for reducing the area of defects, while laying the semi-rigid base layer was beneficial for maintaining the deflection value and rut depth at a lower level.

Tyre Configuration and Axle Load of Front-Wheel Assist and Four-Wheel Drive Tractors Effects on Soil Compaction and Rolling Resistance under No-Tillage

Selecting the appropriate tyre configuration and settings for heavy farm vehicles is important to ensure that soil compaction and power loss in rolling resistance are minimised and traction is optimised. This study investigated the effect of front-wheel assist (FWA, ≈75 kN) and four-wheel drive (4 WD, ≈100 kN) tractors fitted with different tyre configurations (single, dual), tyre sizes and inflation pressures on soil strength (a proxy for soil compaction), and rolling resistance. Single-pass tests were performed on a Typic Argiudoll (≈23% clay, bulk density: 1305 kg m−3) managed under permanent no-tillage. Results showed that average power losses in rolling resistance were 7.5 kN and 5 kN for the 4 WD and FWA tractors, respectively. The average rut depth increased by approximately 1.4 times after a pass of the 4 WD compared with the FWA tractor. The soil cone index (0–600 mm depth) increased from 2023 kPa (before traffic) to 2188 and 2435 kPa after single passes of the FWA and 4WD tractors, respectively (p < 0.05). At the centreline of the tyre rut, dual tyres reduced the soil cone index a little compared with single tyres, but they significantly increased the volume of soil over which soil strength, and therefore soil compaction, was increased. For both tractors (regardless of tyre configuration or settings), soil strength increased to the full measured depth (600 mm), but relative changes before vs. after traffic became progressively smaller with increased soil depth. The power loss in rolling resistance was consistently greater with the heavier tractor, and rut depth was directly related to tyre inflation pressure.

Rutting Performance of Hot Mix Asphalt Using Bagasse Ash as Filler

Transportation plays an important role in the development of a country. Due to the increase in the population, the demand for good transportation and passengers increased. For this purpose, new highways are built up every year. The demand for material for the construction is increasing and the researchers are in the race to find out materials which not only used as a replacer but also increase the strength parameters and decrease destresses in Hot Mix Asphalt pavement. In the present study Sugarcane, Bagasse Ash which is an agricultural waste was used as a filler material. At Optimum Binder Content 4.55 maximum stability of 7.03 KN was achieved while for the samples having stone dust as a filler material give maximum stability at 4.33 percent of 7.37 KN. Bagasse ash used as a filler in Wheel tracker test has given the best result at temperature 300C and the average rut depth was recorded as 2.065mm while stone dust samples showed average rut depth 2.235mm at 30 0Cand the number of passes was recorded as 14000. On the other hand, the samples which are subjected to a temperature of 600C BA samples showed greater rut of the average value of 6.81mm whereas the average value of stone dust samples showed 6.615mm rut depth. From the above results, the author concluded that bagasse is the best modifier material for the areas having low temperature such as 30 0C or below.

Investigating surface condition classification of flexible road pavement using data mining techniques

ABSTRACT The lack of sufficient, accurate and time series dataset on road pavement surface condition in most developing countries over time has posed a serious challenge to highway engineers in terms of developing reliable pavement management system. This study examined the trend of flexible road pavement behaviour and surface condition classification from a historic dataset using intelligent algorithms such as; Random Forest (RF), Decision Tree (DT) and Naïve Bayes (NB) theory implemented in the Waikato Environment for Knowledge Analysis (WEKA) software. Some randomly selected highway links were considered for the investigation. The surface condition attributes considered included the percentage of fatigue cracks, average rut depth and drainage condition in a relatively comprehensive database obtained from the Federal Ministry of Power, Works and Housing Nigeria. Results of the analysis revealed the performance trend and classification of road pavement surface conditions based on surface distresses. The analysis indicated that, the RF and DT algorithms yielded accurate classification against the NB algorithm which could not handle instances of missing data efficiently, hence incurred classification errors. The use of experience-based models that could handle challenges of missing data in a dataset was recommended for the development of road pavement management system using such database.

Use of reacted and activated rubber in ultra-thin hot mixture asphalt overlay for wet-freeze climates

This study investigated the use of crumb rubber in hot mixture asphalt pavement. The two main objectives of this study were to enhance pavement performance in wet-freeze climates and mitigate the environmental issues caused by waste tires. In this study, a reacted and activated rubber modified gap-graded mixture, abbreviated as “RAR-ThinGap”, was designed to improve performance in wet-freeze climates. The concepts behind this design were: an aggregate structure of stone-on-stone contact, a large asphalt film thickness, and elastic rubber fillers. Extensive laboratory tests and field noise measurement had been conducted to determine the properties of this mix. In general, the test results were favorable in regard to moisture damage resistance, low temperature cracking resistance, fatigue cracking resistance, rutting resistance, and noise reduction. The average fracture energy of the RAR-ThinGap mixture was at least four times higher than that of the control mixture at −24 °C. Higher fracture energy indicates an excellent ability to resist thermal cracking in wet-freeze climates. The RAR-ThinGap mix had a fatigue life over 50 times longer than that of the polymer modified SMA mixes or conventional dense-graded mixes. The stone-on-stone skeleton structure of the mixture enhanced the rutting resistance. After 20,000 wheel passes, the average rut depth was 6.80 mm at a test temperature of 50 °C. This RAR-ThinGap mixture may provide an appropriate and environmental-friendly pavement designed for wet-freeze climates.

Soil disturbance by cut-to-length machinery on mid-grained soils

Factors affecting soil disturbance caused by harvester and forwarder were studied on mid-grained soils in Finland. Sample plots were harvested using a one-grip harvester. The harvester operator processed the trees outside the strip roads, and the remaining residues were removed to exclude the covering effect of residues. Thereafter, a loaded forwarder made up to 5 passes over the sample plots. The average rut depth after four machine passes was positively correlated to the volumetric water content at a depth of 0–10 cm in mineral soil, as well as the thickness of the organic layer and the harvester rut depth, and negatively correlated with penetration resistance at depths of both 0–20 cm and 5–40 cm. We present 5 models to predict forwarder rut depth. Four include the cumulative mass driven over a measurement point and combinations of penetration resistance, water content and the depth of organic layer. The fifth model includes harvester rut depth and the cumulative overpassed mass and provided the best fit. Changes in the penetration resistance (PR) were highest at depths of 20–40 cm. Increase in BD and VWC decreased PR, which increased with total overdriven mass. After four to five machine passes PR values started to stabilize.

Mulching and water diversion structures on skid trails: Response of soil physical properties six years after harvesting

In recent years, the application of mulch on machine operating trails has gained popularity as a method of reducing post-harvest soil erosion and water runoff following ground-based harvesting operations. Three treatments immediately applied after ground-based skidding operations were sawdust mulch (SM), water diversion structure or contour-felled log erosion barrier (WDS), and untreated/bare trail (U) in May 2011. At the time of skidding, weather conditions had been very dry and warm. The SM treatment was manually spread on the entire trail surface at a rate of 3.65 kg m−2. WDS was created by placing felled logs with diameters ranging from 25 to 30 cm and 4 m in length in a perpendicular direction to the skid trails with the distance between adjacent WDS set at 10 m. This study aimed to determine and compare the effectiveness of three treatments on the recovery of soil physical properties from compacted soil caused during logging operations over a six-year period (from May 2011 to July 2017) in the Hyrcanian forest, north of Iran. Soil bulk density, total porosity, penetration resistance, and rut depth (wheel rut) were measured to assess the recovery process on three abandoned skid trails with varying longitudinal gradients (10%, 20%, and 30%) exposed to different levels of machine traffic (low, medium, and high). On trails with a 10% gradient, the highest recovery values of bulk density (7.8%) and total porosity (8.5%) were observed in the SM treatment, while on the steepest gradients (20 and 30%), the highest recovery values of bulk density (10.9%) and total porosity (12.9%) were found in the WDS treatment. The average recovery of penetration resistance for soil located in the SM and WDS treatments was 19.1% and 10.5%, respectively. Average rut depth recovery, expressed in percent of post-harvest values, was higher on all trail gradients subjected to the WDS treatment (30.6%) as compared to the SM treatment (13.1%). In general, values of soil bulk density, total porosity, penetration resistance and rut depth continued to show signs of machine-induced disturbance over the 6-year monitoring period, compared to the undisturbed area as a benchmark.

Soil moisture content as a predictor of soil disturbance caused by wheeled forest harvesting machines on soils of the Western Carpathians

Limiting surface soil disturbance caused by forest harvesting machines is an important task and is influenced by the selection of efficient and reliable predictors of such disturbance. Our objective was to determine whether soil moisture content affects soil load bearing capacity and the formation of ruts. Measurements were conducted in six forest stands where various machines operated. We measured the formation of ruts along skid trails in connection with varying soil moisture content. Soil moisture content was determined through the gravimetric sampling method. Our results showed that severe (rut depth 16–25 cm) to very severe disturbance (rut depth >26 cm) occurred in forest stands where the instantaneous soil moisture exceeded its plasticity limits defined through Atterberg limits. Atterberg limits of soil plasticity ranged from 26 to 32 % in individual stands. Regression and correlation analysis confirmed a moderately strong relationship (R = 0.52; p < 0.05) between soil moisture content and average rut depth. This confirmed that soil moisture is a suitable and effective predictor of soil disturbance.

Evaluation of AASHTO T 324 Hamburg-Wheel Track Device test

The Hamburg Wheel-Track Device (HWTD) test has recently gained popularity among many state highway departments of transportation (DOTs) for use in hot mix asphalt (HMA) moisture sensitivity evaluation. In this paper, suggestions are presented to improve and provide more consistent and representative results for this test as described in AASHTOT324 – Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA). In the AASHTOT324 specification, either a cylindrical or a slab specimen can be tested. Use of a two-dimensional micromechanics finite element (2D-MMFE) analysis has demonstrated significant gap/bonding and specimen shape effects on HWTD test results for the cylindrical specimen setup. In addition, the analysis suggests the best method for defining the “rut depth” to ensure consistent results between two specimen setups. Results of this study have concluded that: (1) slab specimens can provide more reliable test results due to larger size and uniform geometry; (2) two cylindrical specimens (cores) should be glued together to prevent localized failure due to larger peak maximum principal strains when there is no bonding; (3) measurements of average rut depth should be collected from stations near the centers of cylindrical specimens to keep the specimen shape effects to the lowest possible level; and, (4) an agency should not allow both specimen setups to be used interchangeably in the HWTD specifications. The investigation also suggests that the average rut depth evolution curve fitted using a three-stage Weibull approach can define the number of passes to failure and define the stripping initiation point (SIP) better than the visually determined SIP.

Rutting progression models for light duty pavements

Deterioration models allow road managers to assess current condition and to predict future conditions of their road networks. Due to heavy vehicle axle repetitions and the effect of environmental factors, permanent deformation (rutting) develops gradually in the wheel paths and impacts on structural and surface performance of flexible pavements. This paper reports the approach adopted to develop absolute deterministic models for permanent deformation of low volume roads. A representative large sample network (23 highways) of light duty pavements was selected. For each section, time series data from four consecutive condition surveys were collected. Multiple regression analysis was carried out to develop models to predict pavement rutting progression over time as a function of a number of contributing variables. They include traffic loading, pavement strength, climate and drainage condition. For more powerful prediction, family group data-fitting approach was utilised to estimate future rutting progression based on the average rut depth curve for a series of pavements with similar characteristics. This study highlighted that separate family deterioration models are preferred and needed for more realistic results. The paper concludes that the analysis approach used for developing the models confirmed their accuracy and reliability by well-fitting to the validation data with low standard error values. Also, study results show that higher traffic loading, lower pavement strength, poor drainage and climates with high seasonal variation contribute to increasing rutting progression rate.

Modification mechanism of high modulus asphalt binders and mixtures performance evaluation

To observe the micro-morphology of high modulus asphalt binders (HMABs), a scanning electron microscope (SEM) and a fluorescence microscope were employed. To evaluate the performance characteristics of mixtures using these binders, laboratory mixture tests were conducted. The binder morphology showed that the particle size of high modulus modifiers, PR PLAST S® (PRS) and PR PLAST Module® (PRM), and the relative viscosity of modified asphalt increased with time; PRS modifier droplets tended to form a network. The test results of the mixtures indicated that compared with the original asphalt mixture and the styrene–butadiene–styrene (SBS) mixture, the HMABs significantly improved the high temperature performance, water stability, moisture–heat synthesis property, and dynamic modulus of mixtures. The investigation results of test sections showed that the average rut depth and surface deflection observed in the test sections using the high modulus asphalt concretes (HMACs) were much smaller than those in the test sections using the SBS mixture after one year of service. Based on the colloidal system equilibrium and the lowest energy principle, the modification mechanism of the HMABs modified by PRS and PRM was analyzed in this paper by using the effects of swelling and interface layer. The effects of the HMABs on the performance of HMACs were evaluated. The test results of the mixtures confirmed the correctness of the analysis associated with the modification mechanism.

Performance Assessment of Geosynthetics and Cement as Subgrade Stabilization Measures

Abstract Work in this paper presents the results of field testing on four instrumented roadway sections constructed on poor subgrade soils and stabilized with select fill, geosynthetics, or cement. Loading was applied using 1000 consecutive truck passes and profile surveying was performed to provide permanent deformation (rutting) data. Peak vertical stresses at the subgrade as well as moisture conditions were also monitored during testing. Results indicated that the deep undercut (31 in./790 mm) with select material backfill section produced the largest cumulative rut depths due to shallow incremental plastic strains induced during each axle pass. The use of a thin Aggregate Base Course (ABC) surface layer (3 in./75 mm) over the select material reduced the rate of rutting. The biaxial geogrid and the high strength geotextile showed a relatively equal performance in all aspects of the study. The cement stabilized section produced a slightly larger average rut depth than the geosynthetically-reinforced sections due to localized areas of pronounced cumulative rutting. However, there were several areas of the soil-cement test section that performed as well as the geosynthetically-reinforced sections.

Reporting Results from the Hamburg Wheel Tracking Device

As the list of states adopting the Hamburg wheel tracking device continues to grow, there is a need to evaluate how the results are used. AASHTO T-324 does not standardize the analysis and reporting of test results. Furthermore, the processing and the reporting of the results of manufacturers are not uniform. This inconsistency is partly the result of the variation of agency reporting requirements. Some requirements include only the midpoint rut depth; others include the average across the entire length of the wheel track. No guidance is given when the stripping infection point (SIP) is reported. To eliminate bias in reporting, statistical analysis was performed on more than 135 test runs on adjoining gyratory specimens. Measurement location was found to be a source of significant variation for rut depth in the Hamburg wheel tracking device. This variation was likely the result of the nonuniform wheel speed across the specimen, geometry of the specimen, and air void profile. Eliminating this source of bias when rutting results are reported is feasible although the feasibility depends on the average rut depth at the final pass. When the results of a test that has an average rut depth of less than 12 mm at the final pass is reported, the average of the measurements along a 6.4-in. path beginning at 0.5 in. from the specimen edge nearest the gear housing should be reported. When the average final-pass rut depth is greater than 12 mm, it is reasonable to report the average of the measurements just off the center of the rutting track along a 3.2-in. path beginning at 2.1 in. from the specimen edge nearest the gear housing. SIP values were also analyzed. It is reasonable to report the average of the SIP values across all locations while calculated values measured more than 2 in. from the specimen's edge are discarded and for cases in which the ratio of the stripping slope to creep slope exceeds 2.0. Validation is needed for multiple machines.

The Effect of Groove–Underside Shaped Concrete Block on Pavement Permanent Deformation

The aim of this study was to investigate the permanent deformation of Concrete Block Pavement (CBP) with the underside surface grooved. Permanent deformation is one of the important factors that influence pavement performance and often happens due to increases in axle load and tire pressure. Such increments have also resulted in greater increment of contact pressure at the tyre–pavement interface. In this study, a new CBP was developed with the concrete blocks grooved at the underside block surface to reduce pavement permanent deformation, termed as Underside Shaped Concrete Blocks (USCB). 13 USCBs were manufactured in the laboratory in this study with their patterns divided into three categories. The CBP models were constructed, from bottom to top, with hard neoprene, 70 mm thick loose bedding sand, and jointing sand which was used to fill in the gaps between USCBs. The test pavement was subjected to 10,000 rounds of load repetition under 1,000 kg single wheel load using the first Malaysian accelerated loading facility called Highway Accelerated Loading Instrument (HALI). The pavement was examined in terms of transverse deformation profile, average rut depth along the wheel path, and longitudinal rut profile other than being visually inspected. Results indicated that permanent deformation is significantly influenced by USCB geometry, groove shape, groove depth, bedding sand settlement during block setting, and load repetitions. From the results, it has been proven that USCB is a potential choice for CBP construction to reduce permanent deformation.

Effects of wheeled cable skidder on rut formation in skid trail — a case study in Hyrcanian forest

The impact of skidding operations on forest soils can be divided into three major categories: soil profile disturbance, soil compaction, and soil puddling and rutting. The present study was designed as a factorial experiment in the Kheyrud Forest with a Timberjack cable skidder to evaluate the influences of number of machine passes and soil moisture of skid trails on rutting over a fine-grained soil, and to quantify these effects. The effects of soil moisture of 20%–30%, 30%–40% and 40%–50% and different levels of compaction were studied. Compaction treatments were applied using different numbers of skidding passes (1, 5, 10, 15, 20, 25, 30 times). Result shows that an increase in the number of machine passes could increase rut depth, but the majority of rutting was occurred after the initial few machine passes. Also rut depth at soil moisture of 40%–50% was higher than rut depths at soil moisture of 30%–40% and 20%–30%. The average rut depth in soil with 20%–30%, 30%–40% and 40%–50% moisture was 17, 22 and 35 cm, respectively. Rut depths were increased significantly with soil moisture and number of machine passes. It is suggested that skidding operations should be planned when soil conditions are dry in order to minimize rutting., but if skidding must be done under wet conditions, the operations should be stopped when machine traffic could create deep ruts.

Investigation of Relationship Between Roughness and Pavement Surface Distress Based on WesTrack Project

Modern pavement rehabilitation and design methodologies require an adequate evaluation of the functional capacity of pavements. A key component of this functional capacity is the roughness of the pavement. The current standard for characterization of a pavement’s roughness is the international roughness index (IRI). Pavement roughness measurements were conducted at regular intervals during the application of approximately 5 million equivalent single-axle loads at the WesTrack Project, a full-scale flexible pavement accelerated loading facility located near Reno, Nevada. The results are presented of an investigation into the relationship between pavement roughness and pavement surface distress using WesTrack data. With a sample population of 317 observations, a relationship was found among the roughness (IRI) and the initial IRI, percentage of fatigue cracking, and average rut depth. A test of the relationship with data collected as a part of the Long-Term Pavement Performance Program indicates favorable results.

Polymer-Modified Asphalt Pavements in Ontario: Performance and Cost-Effectiveness

Two trial sections were constructed to investigate the rutting resistance and low temperature performance of different polymer-modified asphalt (PMA) mixes at sites representative of highways experiencing rutting as a result of heavy traffic loading in cold climatic regions. The two-way average annual daily traffic for both sites was &gt;35,000 (6,000 vehicles per day). Modified asphalts used in the trial sections include engineered bitumen type 306, premium asphalt, reprocessed polyethylene (Novophalt), Neoprene, scrap tire rubber, Vestoplast-S, Kraton 4460, Styrelf, and polyethylene. Representative test samples of aggregates, asphalt cement, modified asphalts, and hot mixes were taken for routine testing during production. In situ quality control tests were done by taking plate samples while laying the mix and by coring after compaction. Additional laboratory tests were done at temperatures ranging from 0°C to —35°C to evaluate the materials’ low temperature cracking resistance. Field performance of trial sections was monitored yearly by crack mapping and measuring transverse profiles at 30-m spacing on each test section. Levels were taken at 100-mm intervals by using a dipstick. A computer program was written to process the data and calculate the rut depths for each wheelpath. Crack mapping was done to assess the crack growth in each test section. The performance of the sections was compared with respect to average rut depth and crack growth. The following are described: (a) the modified mix design chosen specifically to produce accelerated test results, (b) the experience gained in the construction of trial sections, (c) the results of laboratory testing to evaluate the low temperature performance of the PMAs, (d) the field performance evaluation with respect to rutting and cracking, and (e) the life cycle cost analysis. Average rut depth measurements 5 to 7 years after construction show that PMA pavement sections are performing better than conventional asphalt with respect to rutting. With regard to cracking, polymers with 85 to 100 penetration (pen) base asphalt did not perform better than control sections. However, there is an indication that PMA, which has a soft grade (150 to 200 pen) base asphalt, tends to improve low-temperature performance comparable to the control section. In other words, PMA generally performs better than conventional asphalt, provided it contains a soft grade (150 to 200 pen) base asphalt. Life cycle cost analysis indicates that PMA is cost-effective in extending pavement life by 2 to 3 years if the cost of polymer modification does not exceed the cost of conventional asphalt by 100 percent.

Soil Physical Property Changes After Skidder Traffic With Varying Tire Widths

Eight combinations of skidder tires, ranging in total width from 0.7 m to 2.2 m, were evaluated for rut formation potential on two soils in south-central Alabama. One was a mixed pine-hardwood bottomland; the other was an upland, predominantly pine stand. Each soil/tire combination was replicated twice. Changes in soil profile after one, three, seven, and nine loaded passes were used as indices of soil disturbance. The number of skidder passes was the most significant factor influencing rut formation. The effect was linear up to nine passes on both test sites. The first pass on the upland site accounted for half the average rut depth and area. The magnitude of the displacement after one pass was related to tire width. Each subsequent pass caused a uniform smaller increment in depth and area. The magnitude of the increase was independent of tire width. On the bottomland site, however, each pass resulted in an increment in both depth and area the magnitude of which was a function of tire width. Average rut cross-sectional area on the bottomland site ranged from 0.13 m2 to 0.75 m2 for nine passes. Depth of ruts ranged from 1.7 cm to 3.6 cm for nine passes on the upland soil, and from 1.4 cm to 21.2 cm for nine passes on the bottomland soils. Soil physical properties were not affected by skidder traffic regardless of tire width.

On the phase transition in mixed valence type oxides

To observe the micro-morphology of high modulus asphalt binders (HMABs), a scanning electron microscope (SEM) and a fluorescence microscope were employed. To evaluate the performance characteristics of mixtures using these binders, laboratory mixture tests were conducted. The binder morphology showed that the particle size of high modulus modifiers, PR PLAST S® (PRS) and PR PLAST Module® (PRM), and the relative viscosity of modified asphalt increased with time; PRS modifier droplets tended to form a network. The test results of the mixtures indicated that compared with the original asphalt mixture and the styrene–butadiene–styrene (SBS) mixture, the HMABs significantly improved the high temperature performance, water stability, moisture–heat synthesis property, and dynamic modulus of mixtures. The investigation results of test sections showed that the average rut depth and surface deflection observed in the test sections using the high modulus asphalt concretes (HMACs) were much smaller than those in the test sections using the SBS mixture after one year of service. Based on the colloidal system equilibrium and the lowest energy principle, the modification mechanism of the HMABs modified by PRS and PRM was analyzed in this paper by using the effects of swelling and interface layer. The effects of the HMABs on the performance of HMACs were evaluated. The test results of the mixtures confirmed the correctness of the analysis associated with the modification mechanism.