Concrete Pad Research Articles

Impact of Eccentric Loading on the Structural Performance of Reinforced Concrete Pad Footings: An Experimental Study

Setting out of building footings are usually carried out using profile board. This method is usually not accurate in locating the position of columns. Hence, columns that are designed as a concentric columns to their respective footings ends up being columns having eccentricities to the pad footings that supports them. Since the stress distribution under pad footing with concentric column is different from that of pad footing with eccentric column, there is need to study the effect of these eccentricity on the load carrying capacity of the pad footing. In carrying out this work, four pad footings and a typical foundation were used. The pad footings were of sizes 230 mm x 230 mm x 150 mm, with columns of 150 mm x 150 mm cross-section. The first pad footing P1SH was pad footing with short column and zero eccentricity, the second pad footing P2SL was pad footing with slender column and zero eccentricity, the third pad footing P3SL was footing with slender column with 40 mm eccentricity, while the forth pad footing P4SL was footing with slender column with 80 mm eccentricity. The foundation comprises of sand which was contained in a sandbox. The sandbox was made of steel plate of dimensions 0.3 m × 0.3 m × 0.2 m of 4 mm thickness, was used to provide support for the foundation. The foundation was produced by compacting loose sand in three layers with 20 blows per layer in the steel box and with density of about 735 kg/m3. The pad footings were placed on top of the foundation contained in the sandbox, and together were placed on the loading plate of Universal Testing Machine (UTM). Compressive load was applied on each of the pad footings through the columns till failure occurred, using UTM. It was found out that pad footing P1SH have the highest load capacity of 261.25 kN, P2SL pad footing with load capacity of 124.24 kN, P3SL pad footing with load capacity of 39.34 kN, while P4SL pad footing with load capacity of 23.30 kN.

Seismic analysis of free-standing spent-fuel dry storage cask considering soil–concrete pad–cask interaction

This paper presents a seismic analysis method that can evaluate a very large number of cases for the free standing dry storage cask by proposing a methodology that has short analysis time as well as accuracy. This study also performed a seismic analysis of a dry storage facility with multiple casks to show a tip-over phenomenon from earthquake accident conditions. The earthquake accident condition is long-term event that occur during about 20 s long, and lots of seismic analysis cases should be performed to consider various real conditions because the free-standing spent-fuel dry storage cask has many nonlinear responses. The soil–concrete pad–cask interaction was considered in the seismic analysis and finite element model was made using concrete pad, soil and cask models. In the reinforced concrete pad, the rebar was excluded to reduce the analysis time, but the thickness was corrected to maintain the bending rigidity. Additionally, the analysis time reduced by modeling the cask as a rigid body rather than a flexible body. 35-cases of seismic analysis were performed to determine a tip-over phenomenon from each earthquake. The analysis revealed that no tip-over phenomenon of the cask was observed in all analyses from 0.2 g to 0.6 g, however the tip-over of the cask were observed from 0.8 g with friction coefficients of 0.8 and 1.0.

Farm-level risk factors and treatment protocols for lameness in New Zealand dairy cattle

ABSTRACT Aims To identify farm-level risk factors for dairy cow lameness, and to describe lameness treatment protocols used on New Zealand dairy farms. Methods One hundred and nineteen farms from eight veterinary clinics within the major dairying regions of New Zealand were randomly enrolled into a cross-sectional lameness prevalence study. Each farmer completed a questionnaire on lameness risk factors and lameness treatment and management. Trained observers lameness scored cattle on two occasions, between October–December (spring, coinciding with peak lactation for most farms) and between January–March (summer, late lactation for most farms). A four-point (0–3) scoring system was used to assess lameness, with animals with a lameness score (LS) ≥2 defined as lame. At each visit, all lactating animals were scored including animals that had previously been identified lame by the farmer. Associations between the farmer-reported risk factors and lameness were determined using mixed logistic regression models in a Bayesian framework, with farm and score event as random effects. Results A lameness prevalence of 3.5% (2,113/59,631) was reported at the first LS event, and 3.3% (1,861/55,929) at the second LS event. There was a median prevalence of 2.8% (min 0, max 17.0%) from the 119 farms. Most farmers (90/117; 77%) relied on informal identification by farm staff to identify lame animals. On 65% (75/116) of farms, there was no external provider of lame cow treatments, with the farmer carrying out all lame cow treatments. Most farmers had no formal training (69/112; 62%). Animals from farms that used concrete stand-off pads during periods of inclement weather had 1.45 times the odds of lameness compared to animals on farms that did not use concrete stand-off pads (95% equal-tailed credible interval 1.07–1.88). Animals from farms that reported peak lameness incidence from January to June or all year-round, had 0.64 times odds of lameness compared to animals from farms that reported peak lameness incidence from July to December (95% equal-tailed credible interval 0.47–0.88). Conclusions Lameness prevalence was low amongst the enrolled farms. Use of concrete stand-off pads and timing of peak lameness incidence were associated with odds of lameness. Clinical relevance Veterinarians should be encouraging farmers to have formal lameness identification protocols and lameness management plans in place. There is ample opportunity to provide training to farmers for lame cow treatment. Management of cows on stand-off pads should consider the likely impact on lameness.

Bearing Capacity of a Concrete Grouting Pad on the Working Surface of a Highway Tunnel Shaft

A grouting pad is the key structure for the construction of water inrush grouting on the shaft working surface. Previous methods of calculating the bearing capacity have limitations due to a lack of understanding of the failure mode. To investigate the bearing capacity of a concrete grouting pad on the working surface of a shaft, this paper establishes a mechanical model for the punching shear failure of a grouting pad under symmetrical loading conditions. A unified solution for the bearing capacity is derived, and the influence of parameters is discussed. In addition, a new method for designing the plastic limit thickness is proposed based on this research. The results show that the reason for the grouting pads’ punching shear failure resulted from the formation of peripheral grouting holes “weak ring” caused by the reduction of the bearing capacity. When the thickness of B0 remains constant, the bearing capacity qu of the grouting pad is inversely proportional to the ratio of the diameter and the area of the bottom load. Therefore, following the method of “dividing, interval, and jumping holes” during grouting construction is recommended. The greater the thickness of the grouting pad, the greater the bearing capacity qu will be. When the grouting pad diameter is 2r2 and the thickness B0 is constant, the bearing capacity qu increases with the material tensile strength ft. When designing grouting pads, following the principles of “large thickness, uniform strength theory, high strength materials” will improve bearing performance. The findings have been implemented in the design of the grouting pad thickness for the Tianshan Shengli Tunnel shaft project, which can successfully solve the problem of frequent cracking caused by the weak bearing capacity of a grouting pad. The findings can provide a theoretical basis and reference for the design and construction of grouting pads in a highway tunnel shaft.

The Load-Bearing System from the Perspective of Sustainable Building

The building sector has a great potential to achieve goals for sustainable development by promoting environmental quality, economic effectiveness, and social improvement. One aspect that can possibly be considered in this context is the design of the building structure. The purpose of this case study is to investigate how the choice of a load-bearing system of building can affect the amount of concrete and steel reinforcement used in the foundation and its impact on the economy and environment. An alternative structural system of an existing building is proposed. The load-bearing frame walls and spread concrete foundations under walls are replaced by load-bearing timber columns that are placed on separate concrete footing pads. The results show that the amount of concrete and steel in the proposed system have considerably been decreased compared to the reference building. Consequently, this results in minimizing the construction costs as well as the resulting emissions of carbon dioxide into the environment.This case study reviews practical engineering design aspects that can be used by structural and construction engineers to help achieve sustainability goals of the built environment.

Evaluation of mechanically stabilized earth retaining walls for different soil–structure interaction methods: A review

Abstract The method for soil preservation has been completely revolutionized thanks to internally reinforced walls. Although such walls have gained significant awareness in many parts of the globe, this construction technique has only been extensively utilized lately. The primary reason may be that the costs associated with constructing such walls are likely higher than those associated with constructing conventional externally reinforced walls. The construction methods involved may be excessively time demanding. The term “mechanically stabilized Earth systems” refers to an internally stabilized fill structure that is made up of an unreinforced concrete levelling pad, precast concrete face panel units and coping units, selected granular backfill (reinforced backfill), a subsurface drainage system, and reinforcing elements (high-strength, metallic, or polymeric inclusions) to create a reinforced soil mass which is utilized to stabilize the backfill. The purpose of this article is to provide a historical overview of the mechanically stabilized Earth retaining walls by focusing on the necessary aspects required for their design, as well as to discuss how the change of the characteristics of the soil influences lateral displacements and stress responses that occur under various ground movements. The results of this study lead to the conclusion that the dynamic behaviour of the cantilever wall is very sensitive to the frequency characteristics of the seismic record and the interaction between the soil and the structure.

Evaporation of anhydrous ammonia from small concrete coupons and implications regarding evaporation from a large accidental spill on concrete

AbstractAnhydrous ammonia is transported via ship, rail, and road everyday in the United States as a refrigerated liquid at ambient pressure. As a result, unintential release of a large amount of anhydrous ammonia could result from an accident during transportation. The aim of this paper is to provide a better understanding of the evaporation of anhydrous ammonia from porous media. In our investigation, laboratory‐scale concrete coupons were used as a surrogate for a larger concrete pad that could be present in an event involving an unintentional release of liquid anhydrous ammonia. Concrete coupons sized 5 cm × 5 cm × 1.9 cm were saturated in liquid anhydrous ammonia, and measurements of the subsequent evaporation from the coupons were made in an environmental chamber. The ambient air temperature within the chamber varied from 5 to 45°C, and the relative humidity varied from 5% to 75%. Mass‐difference calculation and Berthelot's reaction were used to determine the average evaporation rate from a concrete coupon across all trials, which was found to be 6.5 ± 1.9 mg/s. To validate these evaporation rates, the remaining ammonia in the concrete coupon was measured for each trial. We found that the time‐integrated calculated evaporation rates correlated well with the total mass of ammonia that was lost from the coupons. In addition, it was found that ambient air temperature and relative humidity had little influence on anhydrous ammonia evaporation from the concrete coupons.

The Development of a Backup SOFC Generator at Upstart Power

Upstart Power is developing a state-of-the-art SOFC generator that provides backup power solutions for residential and industrial customers. The Upgen NXG™ fuel cell enables grid independence and pairs seamlessly with solar and/or standalone battery storage to provide extended backup power and 24/7/365 energy solutions. The system has dual fuel capability using either propane or natural gas and exports AC power via Enphase micro-inverters. Field trials are being conducted including a batch of 10 units in Puerto Rico running on propane in collaboration with Sunnova.The key technologies enabling the Upgen NXG™ system’s fast cycling and overall simplicity include:1) Integrated Hot Zone with advanced Thermal Management2) Custom dry CPOx reactor (waterless)3) Control strategy based on two thermocouple setpointsThe core of the NXG system is the Hot Zone which integrates the CPOx reactor, fuel cell stack, heat exchanger, flame sensor, spark ignitor and exhaust system. Figure 1 shows the complete subsystem layout of the NXG system, including the fuel filter, blowers, power electronics and controls. The core component of the Hot Zone is a single piece structure that comprises a thermally conductive element that conducts heat from the combustion chamber to the stack inlet. This enables both rapid start-up and enhanced performance from the stack, without the risk of cell failure due to thermal stress. Figure 2 shows a Hot Zone demonstrating 1000 rapid thermal/power cycles from operating temperature down to 200°C. The chart shows power per cycle with a heat-up time of 40 minutes. Power output was increased after 800 cycles with higher power test cycles run throughout the test.The dry CPOx reactor converts fuel gas into hydrogen and carbon monoxide for use in the fuel cell without the use of any additional water. The CPOx can operate at very low O:C ratios (< 1.2) providing stack fuel efficiencies up to 40% and is controlled by a single thermocouple in the reactor core. The other system control setpoint is the temperature in the core of the hot zone which provides a simple system control scheme with minimal yet reliable sensors.Figure 3 shows real time cycle data from the Upgen NXG™ system, with a start-up time of less than 60 minutes with 9 hours of steady state AC power exporting to the grid via Enphase micro-inverters. The cathode air flow is controlled by the thermocouple in the core of the Hot Zone (Radiated).In summary, the Upgen backup power systems outperform ICE generators and battery-only backup by providing unlimited backup solar + storage systems that are more robust, cost-effective and have lower emissions. The single wall mounted unit minimizes connections and simplifies installation over an ICE generator that typically sits on an outdoor concrete pad. With near silent operation and the absence of deadly CO emissions, the Upgen NXG™ is a safe and environmentally friendly backup power solution for residential solar and industrial customers. Figure 1

Evaluation of sealants to mitigate the release of per- and polyfluoroalkyl substances (PFAS) from AFFF-impacted concrete: Characterization and forecasting

Per- and polyfluoroalkyl substances (PFAS) within concrete pads impacted by historical firefighting training using aqueous film-forming foam (AFFF) may be potential secondary sources of PFAS due to surficial leaching. This study aimed to (i) characterize the effectiveness of two commercially available sealants (Product A and Product B) in mitigating leaching of five PFAS (e.g., PFOS, PFOA, PFHxS, PFHxA, 6:2 FTS) from concrete surfaces at the laboratory-scale, and (ii) develop a model to forecast cumulative leaching of the same five PFAS over 20 years from sealed and unsealed concrete surfaces. Laboratory trials demonstrated that both sealants reduced the surficial leaching of the five PFAS studied, and Product B demonstrated a comparatively greater reduction in surface leaching than Product A as measured against unsealed controls. The cumulative PFOS leaching from an unsealed concrete surface is estimated by the model to be about 400 mg/m2 over 20 years and reached asymptotic conditions after 15 years. In contrast, the model output suggests asymptotic conditions were not achieved within the modeled time of 20 years after sealing with Product A and 85% of PFOS was predicted to have leached (∼340 mg/m2). Negligible leaching of PFOS after sealing with Product B was observed ( < 5 × 10−9 mg/m2). Results from modeled rainfall scenarios suggest PFAS leachability is reduced from sealed versus unsealed AFFF-impacted concrete surfaces.

Economical Curing Method by Curing Pad for Beam

Abstract: Efficient uninterrupted curing is a key to quality concrete. Proper curing of concrete is crucial to obtain design strength and maximum durability considering the cost of curing. Curing is designed primarily to keep the concrete moist, by preventing the loss of moisture from the concrete during the period in which it gains strength. Due to rising problem of scarcity of water and expensive conventional methods of curing, it had become necessary to build-up a new method for concrete curing. This paper represents the experimental work related to a newly developed, effective and economical method of beam curing. This method consists of a technology namely ‘Curing Pad’ that not only absorbs and retains water for an extended period of time but also reduces evaporation losses. Concrete pad consists of 3 layers. The top layer is of a reflector material that reduces evaporation losses. The middle layer comprises of an absorbent material that stores and transmits water to the concrete beam. Bottom layer is binding or packing layer that holds all three layers together. Various tests are performed to check the durability of Curing Pad as well as its performance on concrete beam. These test results are compared to those of ponding method of beam curing.

Case Study: Effect of mechanical short-circuiting of isolation pads on rooftop equipment noise and vibration transfer to spaces below.

The authors conducted investigations into noise from large rooftop air source heat pump (HP) equipment to student housing units below in a new concrete building. The investigation included both airborne noise and vibration measurements on the roof and in the dwelling units below. A total of five, 18-Ton devices were mounted on a foam-filled concrete housekeeping pad resting on an 8-inch thick PT structural slab and isolated by means of spring mounts fitted with neoprene isolation pads below their baseplate. The dwelling units below had exposed concrete at the ceiling, shear walls, and columns. Noise from the HPs were waking residents in the units directly below the equipment. After a number of adjustments to the spring isolation mounts to eliminate bindings and mechanical short-circuits, the investigation showed that vibration was also being transmitted to the building structure from the isolator base plates through the anchor bolts, bypassing the noise pads below the baseplate. Removal of this secondary short-circuit resulted in noticeable reductions in both noise and vibration at the spaces below, highlighting the need for careful adjustment and the provision of additional isolation elements in the installation.

Quantification of the variability and penetration of per- and poly-fluoroalkyl substances through a concrete pad

Historical use of aqueous film forming foams (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) for fire-fighting activities has contributed to widespread contamination of infrastructure which can represent an ongoing source of PFAS to the surrounding environment. A concrete fire training pad with historical use of Ansulite and Lightwater AFFF formulations had PFAS concentrations measured to quantify spatial variability of PFAS within the pad. Surface chips and whole cores of concrete through to the underlying aggregate base were collected over the 24 × 9 m concrete pad and depth profiles of PFAS concentrations in nine cores were analysed. PFOS and PFHxS dominated the PFAS for surface samples, along the depth profile of cores and in the underlying plastic and aggregate material, with substantial variability in the concentrations of PFAS in the samples. Although there was variability of individual PFAS along the depth profile, higher surface concentrations of PFAS generally followed the designed movement of water across the pad. Total oxidisable precursor (TOP) assessments of one core indicated additional PFAS were present along the entire length of the core. This study highlights concentrations of PFAS (up to low μg/kg) from historical use of AFFF can occur throughout concrete, with the variable concentrations throughout the profile.

Dry Parallel Seismic: A Novel Method for Determining Thickness of Buried Concrete Pad Foundations

The structural capacity of concrete foundations supporting, for example, telecommunications and electrical transmission towers depends, among other things, upon the thickness of the concrete foundation. Current methodology for investigating the thickness of concrete foundations nondestructively has largely been focused upon deep foundations, such as caissons, and in situations where the top of the foundation is exposed. For example, the parallel seismic (PS) method is a borehole method that uses the arrival times of waves imparted in a foundation at a sensor next to a buried foundation to detect the thickness of the foundation but is typically used for deep caisson type foundations. However, in many instances, these foundations are pad and pier type footings that can be buried deep below ground and can be relatively thin, for example, less than 45 cm in thickness. The objective of the present work is to present a nondestructive method for determining the thickness of concrete pads with no direct access. The dry PS method was developed to determine the thickness of thin, buried concrete foundations. The method was first used to verify the as-built thickness, as mentioned in the engineering drawings of a guyed tower dead-man block. Second, it was used to determine the thickness of the pad foundations of five telecommunication towers with pad and pier concrete foundations in South Asia. These towers had foundation thicknesses ranging from 16 to 36 cm, as verified through excavation. Analysis of the data collected during dry PS testing resulted in a mean absolute error (MAE) of 18 mm, which equates to approximately 6% error. Thus, this paper demonstrates that the dry PS method overcomes the limitations of the current methodology and is capable of accurately determining the thickness of buried concrete foundations.

Prospects of Consumer-Grade UAVs for Overpass Bridges Pier Pads Alignment

The use of Unmanned Aerial Vehicles (UAVs) for surveying is at the forefront of their use in the Architectural Engineering and Construction (AEC) industry. UAVs make accessing hard-to-reach construction regions simpler and more cost-effective because of their small size, ease of mobility, and the wealth of information given by their integrated sensors. Accordingly, their use is thriving in different AEC sectors such as the management and inspection of engineering facilities such as concrete bridges. Overpass bridge engineering inspections are still applied using high accuracy surveying instruments in situ to ensure meeting the quality standards of construction. One important application is to measure the bridge pier caps centerline fitting using total stations, which is costly in terms of time and labor. Therefore, in this article, a new approach based on consumer-grade UAV imaging is proposed for replacing the traditional surveying techniques which are expected to improve automation and reduce time and cost. The proposed method utilized a sequence of processes on the UAV point clouds of the bridge concrete pier caps to finally extract the pier pads center and check their alignment. In two experiments, point clouds are created using DJI Phantom 3 images taken over bridge pier projects under construction, and concrete pad centers are then estimated and compared to the reference total station measurements. The results of both tests reveal the ability of the proposed method to attain the required accuracy for the pads’ alignment, as the root mean square error (RMSE) is one centimeter and two centimeters for the first and second tests, respectively. In addition, the new approach can reduce implementation time and the project budget.

Use of Movable Bus Stop Loading Pads: Feasibility and Design Alternatives

The Americans with Disabilities Act (ADA) of 1990 requires bus stops to be accessible for individuals with disabilities. At a minimum, bus stops must have firm, stable, slip-resistant loading pads with connected sidewalks and curb ramps. Consequently, the typical approach of transit agencies has been to install permanent concrete loading pads at bus stops. This study explored alternatives to conventional concrete pads with movable pads that could be installed quickly, resulting in savings in construction and labor costs and minimizing both disruptions to traffic and impacts to abutting businesses. Potential design alternatives in terms of materials and structural support for these pads were evaluated. The review focused on existing and alternative design materials, especially in applications other than for transit purposes. Six materials were evaluated based on their structural performance, long-term durability, adaptability, life cycle cost, aesthetics, and safety and accessibility of transit riders with mobility devices. Of the six materials, plastic lumber and metal were found to have the highest potential to replace conventional designs. Two design alternatives that rely on the concept of bridge construction were introduced, both of which consist of four major components: foundation, slab, beam, and connections. These new design alternatives are anticipated to minimize maintenance of traffic and the need for heavy machinery to excavate, fill, and/or compact the soil.

Experimental and Seismic Response Study of Laminated Rubber Bearings Considering Different Friction Interfaces

Unbonded LRBs (laminated rubber bearings) are commonly applied in small-to-medium-span bridges in China. The frictional sliding characteristics of LRBs have a vital influence on the seismic response of the bridge. Nine square LRBs were subjected to the quasi-static displacement loading test in this paper, and the differences in sliding characteristics of LRBs at the interface of steel and concrete test pad were investigated. The variation of the friction coefficient during sliding was then analyzed. Based on the experimental data, a three-fold mechanical constitutive model of LRBs that considers the breakaway-sliding friction characteristics is established. Further, the bridge seismic demands in longitudinal directions with different friction interfaces are compared by nonlinear dynamic analysis on a typical LRB-supported concrete bridge. The results show the causalities of the displacements and decreases of the friction coefficient of the LRB. The breakaway coefficient of friction of the concrete surface was generally greater than that of the steel in the pre-sliding stage, while the sliding coefficient of friction of the steel interface in the post-sliding stage was greater than that of the concrete. Moreover, the proposed three-fold constitutive model is able to simulate the frictional sliding behavior of LRBs accurately. Lastly, the seismic design of small-to-medium-span bridges should take into account the breakaway-sliding friction effect of the LRBs and the preference for steel as friction pads for LRBs is recommended.

Evaluating performance of carbon fiber-reinforced pavement with embedded sensors using destructive and non-destructive testing

Installation of concrete pavement at the curb travel lane at the bus stop is a common way to improve the resistance of bus pads to environmental and petroleum deterioration in Canada. The Satisfactory condition of concrete pavements remains a key consideration in the development of infrastructure, especially in countries with an aggressive environment. Innovative materials that could remarkably increase the service life of infrastructure are being researched and developed over decades. This paper aggregates the real-time comparison between the performance of a carbon fiber-reinforced concrete (CFRC) bus pad and a normal concrete bus pad. A series of wireless sensors such as temperature and humidity sensors, thermocouples and strain gauges were embedded in both pavements during the construction. Additionally, a series of six piezoelectric patches were embedded in the concrete in each bus pad. Visual monitoring exhibited that the carbon fiber-reinforced bus-pad remained cracked free while exhibiting some balling of carbon fibers on the surface of pavement whereas the normal concrete bus pads exhibited several hairline cracks in the first 10 days of construction. Along with the visual monitoring using a thermal imaging camera (FLIR), data was acquired regularly from both bus-pads at regular intervals. After 28 days of construction, Non-destructive tests (NDT) including Schmidt Hammer (SH), Electrical Resistivity (ER) and Ultrasonic Pulse Velocity (UPV) were conducted on both the bus pads. When compared to normal concrete bus pads, which have electrical resistivities of roughly 30 kΩ-cm, CFRC bus pads showed extremely low electrical resistivity. Schmidt hammer and UPV both revealed degradation in the normal concrete bus pad in comparison to the CFRC bus pad. Several clusters of very low UPV values were observed in the location of bus pad cracks. The lesser values in the CFRC bus pad are indicative of the scatter in the wave energy due to the presence of carbon fibers.

Fibre Mesh in Reinforced Slabs

Abstract: Fiber Reinforced Concrete is gaining attention as an effective way to improve the performance of concrete. Fibers are currently being specified in tunneling, bridge decks, pavements, loading docks, thin unbonded overlays, concrete pads, and concretes slabs. These applications of fiber reinforced concrete are becoming increasingly popular and are exhibiting excellent performance The usefulness of fiber reinforced concrete in various civil engineering applications is indisputable. Fiber reinforced concrete has so far been successfully used in slabs on grade, architectural panels, precast products, offshore structures, structures in seismic regions, thin and thick repairs, crash barriers, footings, hydraulic structures and many other applications. This study presents understanding srength of fibre reinforced conceret. Mechanical properties and durability of fiber reinforced concrete.

The behavior of the Perbaungan railway subgrade

Railway subgrade is a layer consisting of soil material which can be in the form of natural soil, repaired material, and in the form of embankment of selected soil material that meets the specifications. The subgrade that meets the requirements is soil with a minimum CBR value of 8% with a minimum thickness of 30 cm. This study aims to analyze and evaluate the CBR value of the railway subgrade. Subgrade analysis was carried out on the improvement of the railway - replacement of concrete pads and rails R.25/33/42 to R.54 concrete pads from km 39 + 100 to km 40 + 200 along 1100 m in Perbaungan North Sumatra. The structure of the soil layer that is analyzed is the structure of the subsoil in the form of subgrade. The CBR value of the subgrade in the form of soil is determined based on the results of the analysis of the DCP data. The CBR value is evaluated based on the provisions that apply to the railway subgrade. The behavior of the railway subgrade can be seen from the CBR value of the original subgrade. Based on the results of the analysis, it was found that the behavior of the railway subgrade was quite diverse and it was found that only 39% met the requirements for the rail subgrade. Handling carried out in the field to improve the behavior of the subgrade is by using a backfill system made of good material with a density and CBR value that meets the requirements for railways.

Siricid Parasitoids (Hymenoptera: Ichneumonidae) From Eastern White Pine and Associated Pine Species in Southern Appalachia

Siricid Parasitoids (Hymenoptera: Ichneumonidae) From Eastern White Pine and Associated Pine Species in Southern Appalachia