复合土钉技术在软土深基坑支护中的应用

结合工程实例，对支护方案的选用及其设计参数进行了介绍，并对基坑支护结构验算进行了计算分析，对复合土钉施工技术进行了详细阐述，施工监测结果表明，复合土钉支护方案可行，降低了工程造价，缩短了施工工期。     

浅谈仓库设计中的细节

对仓库进行了详细分类，并对仓库的设计过程进行了讲解，收集了相关的设计资料，指出了每个环节容易出现的问题，结合实例对仓库设计进行了总结与探讨，以更好地利用土地设计出经济合理、美观大方的仓库。     

一种新型锻锤隔振基础的设计和分析

本文对自由锻锤隔振基础的结构系统，主要元件及其性能进行了简要介绍，对锻锤隔振基础机理进行了分析，并对主要元件的参数选择，力学模型的建立进行了探讨．     

加筋土挡墙的应用与发展

对加筋土挡墙进行了介绍，简要阐述了加筋土挡墙的研究发展现状，对加筋土挡墙的计算方法和设计理论的优缺点进行了一些讨论，并对其发展进行了展望，从而促进加筋土挡墙的研究和应用。     

粘土铺盖法在水利水电工程中的分析应用探讨

本文结合笔者多年水利水电工程施工实践，从粘土铺盖法的原理和适用条件入手，详细介绍了粘土的选用条件，并对粘土力学性质和渗透稳定性进行了分析，对施工方案设计进行了具体论述，对施工效果进行了综合评价。     

灌浆的机理与分类

本文提出了占位和有界性两个新概念，依据它们对灌浆定义重新进行了阐述，不仅对灌浆原有的分类方法进行了修正，而且从这两个概念出发重新对灌浆进行了分类，同时阐述了灌浆的机理及应用问题。     

南水北调工程项目工期和费用影响因素的定量研究

首先对影响南水北调工程项目延期和超支的关键因素进行了问卷调查，利用SPSS统计软件对其信度进行了检验。在确保问卷可靠性的基础上，对所涉及的诸多影响因素进行了影响严重程度评价和排序，同时利Cox-Stuart趋势增长检验方法进行了检验，得到对南水北调工程超支和延期影响均很严重的前6项关键因素，并针对其中两项提出了相关的政策性建议。另外，还利Pearson相关系数法对延期与超支之间的相关性进行了检验，充分证明了延期与超支之间存在很强的相关性。     

建筑节能背景下暖通空调技术意义及实践探究

随着社会进步，全球的气候逐渐开始变暖，人类所处的自然环境也逐步恶化，全世界加大了对节能建筑的重视。，因此，要加大对暖通空调技术的研究和创新。本文对建筑节能背景下的暖通空调技术的发展现状进行了分析，并据此提出了研究其技术的意义，同时，还对技术设计的原则进行了说明，并对技术的具体实践进行了阐述。     

柱下独立基础抗弯强度计算探讨

本文对柱下独立基础抗弯强度计算进行了探讨，指出了现行计算方法和公式对偏心受压基础偏于不安全，在原假定条件下，推导出抗弯强度的计算公式，对现行公式的误差进行了分析，并通过算例对两种方法进行了比较．     

谈小火电企业的成本控制

对成本控制的发展进行了简单介绍，并对全员目标成本管理的原理及其推行的作用进行了阐述，对小火电全员目标成本管理的创新进行了探讨，有效地提高了企业的经济效益。     

Measuring low permeabilities of gas-sands and shales using a pressure transmission technique

Liquid and gas permeability measurements for tight gas-sand and shales were done using a pressure transmission technique in specially designed apparatus in which confining pressure, pore pressure, and temperature are independently controlled. Downstream pressure changes were measured after increasing and maintaining upstream pressure constant. The initial pressure difference changes only after the pressure pulse propagates across the sample. For low permeability samples, the downstream pressure increase is delayed but the measurement senses a greater sample volume. On the other hand, conventional pulse decay techniques provide a more rapid response but are sensitive to local sample permeability heterogeneity. Permeability measured for the rocks studied varies from 1.18×10⁻¹⁵ to 3.95×10⁻²¹ m². The measured permeability anisotropy ratio in gas shale varies from 20% to 31%. The magnitudes of permeability anisotropy remain almost constant, but the absolute permeability values decrease by a factor of 10 with a 29.79 MPa effective pressure. All samples showed a nonlinear reduction in permeability with increasing effective pressure. The rate of reduction is markedly different from sample to sample and with flow direction. This reduction can be described by a cubic k–σ law and explained by preferential flow through microcracks.     

The influence of a low air pressure environment on human metabolic rate during short‐term (< 2 h) exposures

Passengers in aircraft cabins are exposed to low‐pressure environments. One of the missing links in the research on thermal comfort under cabin conditions is the influence of low air pressure on the metabolic rate. In this research, we simulated the cabin pressure regime in a chamber in which the pressure level could be controlled. Three pressure levels (101/85/70 kPa) were tested to investigate how metabolic rate changed at different pressure levels. The results show that as pressure decreased, the respiratory flow rate (RFR) at standard condition (STPD: 0°C, 101 kPa) significantly decreased. Yet the oxygen (O₂) consumption and carbon dioxide (CO₂) production significantly increased, as reflected in the larger concentration difference between inhaled and exhaled air. A significant increase in the respiratory quotient (RQ) was also observed. For metabolic rate, no significant increase (P > 0.05) was detected when pressure decreased from 101 kPa to 85 kPa; however, the increase associated with a pressure decrease from 85 kPa to 70kPa was significant (P < 0.05). Empirical equations describing the above parameters are provided, which can be helpful for thermal comfort assessment in short‐haul flights.     

Characteristics of air pressure fluctuations in high-rise drainage stacks

Maximum air pressure in a drainage stack can deplete the appliance water trap seals that prevent the ingress of foul gases and odors into a habitable space. This study investigates the air pressure fluctuation frequency, as well as the maximum and average air pressures with their respective standard deviations, in a 38 m high drainage stack of a full-scale experimental tower under steady flow conditions of flow rates 1 Ls⁻¹ to 4 Ls⁻¹ discharging at a height between 15 m to 33 m above the stack base. Mathematical expressions are proposed to correlate the maximum air pressure with the probability density function of the data measured. The average prediction and the maximum under-prediction of the absolute peak pressure were determined with the margin of error taken within certain confidence levels. It was demonstrated that water seal failure would likely be occurred at some heights below the discharge locations. The outcome enhances the understanding of the characteristics of air pressure fluctuation within a drainage stack of a high-rise building.     

Correlations of control parameters determining pressure distributions in a vertical exhaust shaft

The pressure distribution in a vertical exhaust shaft is important in determining the ventilation performances of local exhaust hoods in high-rise buildings. Uneven pressure distribution can cause insufficient exhaust airflows from hood fans, and can cause excessive exfiltration resulting in unwanted noise through any gap openings. There are various system parameters that affect the pressure distribution in a vertical shaft, such as building height, shaft size, roof fan characteristics, concurrent hood fan usage, and outdoor temperature. The objective of this study is to quantify and investigate the effects of these parameters numerically on the overall ventilation performance of a vertical shaft. In order to achieve this goal, specialized simulation software has been developed, which implements the principles of fluid dynamics in vertical air columns with horizontal branches. Simulation results have been obtained based on a model of a 25-story apartment building, according to the experimental design method. Analysis of the variance has been conducted to investigate any correlations between the parameters. The results show that the deviation of the pressure distribution based on a slight negative value (i.e. −30 Pa or −40 Pa) has a strong correlation with the maximum pressure in the shaft. This indicates the possibility of using the pressure deviation as a single objective parameter, which represents both the insufficiency and unevenness of the pressure distribution throughout the shaft. Roof fan rpm and inlet damper opening can be used as operational parameters, and the pressure and pressure gradient at the top-most level, and outside temperature can be used as sensing parameters for pressure control in a vertical shaft.     

Net pressures on the roof of a low-rise building with wall openings

This paper deals with an investigation of the characteristics of net pressures on two significant roof areas of a low-rise building with two different dominant wall openings. Wind tunnel boundary layer studies were conducted on a corner and a gable-end roof area of a 1:50 geometric scale model of the Texas Tech University (TTU) test building with a corner and a central wall opening. Mean and peak pressure coefficients, RMS values for the pressure coefficient fluctuations about their mean, as well as roof external pressure—internal pressure correlation coefficients were obtained for the entire 360° wind azimuth range. Frequency domain studies were also conducted for a few selected point roof pressure situations from which the frequency-dependent roof external pressure—internal pressure phase difference functions, root coherence functions and the spectral density functions were obtained. The results show that the mean, RMS and peak net pressure coefficients are particularly enhanced relative to the coefficients for the roof external pressure in the ±50° wind range. Zero-time-lag correlation coefficients of up to −0.64 were obtained in agreement with results from past studies, while root coherence values of up to 0.7 were also recorded. It is demonstrated that the provisions of both the Australian/New Zealand wind loading code—the AS/NZS1170.2:2002, and the American wind loading code—the ASCE7-02, are sometimes non-conservative in the prediction of mean and peak net roof pressure coefficients. These are believed to be due to non-conservative internal pressure coefficients allowed for in these codes.     

Determination of the pressure of backfill soil against retaining walls on a centrifugal machine

Conclusions 1. Use of the method of centrifugal modeling in studying lateral soil pressure on retaining walls makes it possible to ascertain not only general laws governing the formation of lateral pressure, but also the character of its variation as a result of technological peculiarities of the soil's placement in the backfill. 2. The curve of lateral soil pressure that is formed in the initial period does not change thereafter with increasing height of backfill and increasing stresses, i.e., the quality of backfill placement determines the lateral pressure over the entire period of subsequent service. 3. The initial density of the backfill soil significantly affects the lateral soil pressure in the state of repose (for a stationary wall). The higher the initial density, the lower the coefficient ξ, and conversely. For noncohesive soils, the maximum pressure was observed for an uncompacted backfill (ξ=0.42−0.45). 4. An active soil pressure, which is approximately 25% lower than the pressure at rest, is formed in the backfill as the top of the wall departs from it by the amount (1/100)H – (1/200)H. 5. As the wall departs from the soil and subsequently returns, its lateral pressure in the initial position does not return to the initial value, and a reactive soil resistance begins to form at once. For wall deformations, consequently, the backfill must be treated as an elastic medium. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 18–20, September-October, 1990.     

Hydraulic fracture reopening pressure and the estimation of maximum horizontal stress

In hydrofracture stress measurements, the magnitude of the maximum horizontal stress, S_H, is commonly estimated from the borehole pressure required to reopen an induced axial crack. Examination of the processes which govern the borehole pressure history recorded during the reopening cycle of such tests indicates two sources of error in the estimates of S_H derived using the conventional method proposed by Bredehoeft et al. [Bredehoeft JD, Wolff RG, Keys WS and Shutter E, 1976, Colorado. Geol. Soc. Amer. Bull., 87, 250–8]. The first arises from the failure to include a term arising from pressure penetration into the crack prior to reopening in the force balance acting across the mouth of the induced axial cracks. The problem can be remedied by using a modified ‘reopening equation’ which includes pressure penetration of the crack. The second source of error is more problematic and concerns the correct identification of the true reopening pressure from the borehole pressure records. Analysis of the process of reopening aided by numerical simulations shows that the true reopening pressure is generally less than the apparent (i.e. that detected) reopening pressure. The discrepancy between true and apparent reopening pressures increases with larger hydraulic compliance of the test equipment. The compliance in question refers to that of the fluid volume between the flow meter and the crack mouth(s). Simulation of a pair of 1 m high axial cracks with 2 μm residual hydraulic aperture in a 100 mm borehole, indicates that the system compliance must be reduced to 5×10⁻⁷ m³/MPa to enable the true reopening pressure to be estimated to better than 10%, at flow rate is less than 10⁻⁴ m³/s. This is several orders of magnitude less than applies to conventional hydrofracture systems, but is attainable for tests in small holes at shallow depth by making relatively minor system modifications. Tests at greater depth, however, would seem to require downhole measurement of flow at the packers. We validate our assertions with a field test in which reopening pressure was determined mechanically and hydraulically.     

Behavior of a mechanically anchored waterproofing membrane system under wind suction and uniform Pressure

A pressure and wind tunnel test was conducted to obtain the basic data for wind resistance design of a mechanically anchored waterproofing membrane system. The test specimen was a flat roof with the following dimensions: 2.4 m in width, 3 m in length and 0.29 m in height. The waterproofing material was polyvinyl chloride sheet reinforced with polyester fiber (PVC sheets). In the pressure test, because the applied pressure was equivalent to the pressure on the entire surface area of the roof, the billowing heights of the PVC sheet around the fastener had almost the same maximum values; therefore, the axial force at the fastener was also similar to the pressure induced by a compressor, and no lateral forces were measured. On the other hand, in the wind tunnel test, the strain of the PVC sheet around the fastener at windward side was larger than that of the leeward side. The lateral force was 70% of the axial force at a mean wind speed of 38.6 m/s. Therefore, it was clear that the characteristics of the mechanically anchored waterproofing membrane system in the pressure test and the wind tunnel test were different.     

On the pressure dependence of flammability limits of CH2=CFCF3, CH2F2 and methane

Flammability limits of CH₂=CFCF₃ (HFO-1234 yf), CH₂F₂ (HFC-32), and methane were measured at pressures from ambient to 2500 kPa in a 5 l stainless-steel spherical vessel. For HFO-1234 yf, as the pressure rises from ambient, the lower flammability limit is shifted downward and the upper limit is shifted upward. The changes to the lower flammability limits are, in general, small compared to the upper flammability limits. Both the lower and upper flammability limits of this compound can be approximated by simple logarithmic functions of pressure. For HFC-32, the behavior of lower flammability limit is similar to that for HFO-1234 yf, but the behavior for the upper limit is rather complicated. As the pressure is increased, it begins to rise upward gradually. Then, as the pressure becomes larger than about 1000 kPa it begins to rise upward rapidly, and then the change becomes moderate again. This must be due to a change of combustion reaction mechanism below 1000 kPa and above 1500 kPa in the upper flammability limit region for this compound. On the other hand, both the flammability limits of methane change almost linearly with pressure, at least in the pressure region considered.     

A numerical investigation into the effect of Windvent louvre external angle on passive stack ventilation performance

The Windvent is a commercially available passive ventilation device. The device is constructed from sheet metal and works on the principle of pressure differential. Whereby warm air rises, creating a low pressure in the receiving room, which then draws in the fresh air. This paper investigates the effect of altering the external angle of the Windvent louvres against the internal pressure and velocity within the device and the microclimate velocity. Numerical analysis is carried out using a commercial Computational Fluid Dynamics (CFD) code, to investigate the effect of various louvre angles (range 10–45°) on pressure and velocity to optimise the device performance. The results show that the louvre performance mimics that of thin airfoil from aerodynamic theory. The relationship between trailing-edge stall and delivery velocity is established. The optimum louvre angle with a prevailing wind velocity of 4.5 m/s is shown to be 35° with a stall angle of 40° illustrated. The external, performance enhancing louvre angle, determined through this investigation is subject to UK patent number 0809311.4.