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Re: Modulus of subgrade reaction[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org
- Subject: Re: Modulus of subgrade reaction
- From: James_F_Fulton(--nospam--at)rohmhaas.com (James F Fulton)
- Date: Thu, 12 Feb 1998 14:42:29 -0500
The values you quote, which appear in Table 2-7 of that particular edition, are not modulus of subgrade reaction, which incidentally has units of force per length cubed. For example, "pci" would mean psi of bearing pressure per inch of displacement. Therefore, 1 pci means that 1 psi of bearing produces 1 inch displacement of the soil surface. Be careful when using "k" values out of a text and applying them to something large like say mat foundation, for example. Many times the values given are for a 1'x1' plate they have to be reduced for a mat foundation using formulas originally reported by Terzagi in his 1955 paper on the subject. Soil texts such as Bowles usually give these equations, which are different for clays and sands. The reductions are significant ! For example, for a soil with a 1x1 plate value of say 300 pci, when applied to a 60 ft. sq. mat, the "k" value for use in the analysis is 5 pci according to the Terzaghi equations. Rather than use the 1'x1' values as a base, I personally rather do (or use from a Geotech report) a settlement calc for the particular soil using standard mentods, and to then divided the bearing pressure by the predicted displacement to obtain a "k" value. The resulting "k" value will be different over the loaded area, and then one has a choice of using non-uniform k's in a program such as PCA MATS, which allows that, or using a single value of k in an analysis. Obviously, judgement is needed when doing this because you would like to minimize the number of different k's input into the analysis, and some mat analysis programs such as ELAMAT can accept only one K value, which is then applied uniformly over the mat in the analysis. ______________________________ Reply Separator _________________________________ Subject: Re: Modulus of subgrade reaction Author: seaoc(--nospam--at)seaoc.org at Internet Date: 2/12/98 8:27 AM >From Bowles, "Foundation Analysis and Design", 4th ed: Sand: Silty: 150-450 ksf Loose: 200-500 ksf Dense: 1000-1700 ksf Lew Midlam, PE http://www.lcm.com ======================== Shafat Qazi wrote: > Question: > > Can anyone tell me what is a standard value for the modulus of subgrade > reaction for soil type S2?
Received: from rhmail.rohmhaas.com (126.96.36.199) by ima-gw.rohmhaas.com with SMTP (IMA Internet Exchange 2.1 Enterprise) id 002120C1; Thu, 12 Feb 98 08:49:37 -0500 Received: from nmho05e.rohmhaas.com by rhmail.rohmhaas.com (AIX 3.2/UCB 5.64/4.03) id AA59900; Thu, 12 Feb 1998 08:30:39 -0500 Received: by nmho05u.rohmhaas.com; id IAA10657; Thu, 12 Feb 1998 08:57:52 -0500 (EST) Received: from unknown(188.8.131.52) by nmho05u.rohmhaas.com via smap (3.2) id xma010630; Thu, 12 Feb 98 08:57:30 -0500 Received: from [184.108.40.206] by server1.seaoc.org (NTList 3.02.13) id ba141701; Thu, 12 Feb 1998 05:32:13 -0800 Received: from hugin.request.net ([220.127.116.11]) by eshu.request.net with ESMTP id <998-8206>; Thu, 12 Feb 1998 08:25:52 -0500 Received: from comm ([18.104.22.168]) by hugin.request.net with SMTP id <34731776-10139>; Thu, 12 Feb 1998 08:25:44 -0500 Received: from lcm.com [192.168.0.2] by comm [192.168.0.1] with SMTP (MDaemon.v2.6.rA.b6.32-R) for <seaoc(--nospam--at)seaoc.org>; Thu, 12 Feb 98 08:25:55 -0500 Message-Id: <34E2F8AF.9EA9CB5F(--nospam--at)lcm.com> Date: Thu, 12 Feb 1998 08:27:11 -0500 From: Lew Midlam <Lew.Midlam(--nospam--at)lcm.com> Organization: LCM Engineering, Inc. X-Mailer: Mozilla 4.04 [en] (WinNT; I) Mime-Version: 1.0 To: seaoc(--nospam--at)seaoc.org Subject: Re: Modulus of subgrade reaction References: <22.214.171.124.19980211151535.00a15d40(--nospam--at)seaoc.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mdaemon-Deliver-To: seaoc(--nospam--at)seaoc.org Reply-To: seaoc(--nospam--at)seaoc.org Error-To: seaoc-ad(--nospam--at)seaoc.org X-Loop: seaoc(--nospam--at)seaoc.org X-Info: [SEAOC] Owner: seaoc-ad(--nospam--at)seaoc.org X-Pop3-Rcpt: seaoc-ad(--nospam--at)seaoc.org X-Sender: seaoc-ad(--nospam--at)seaoc.org Precedence: list X-Listmember: James_F_Fulton(--nospam--at)rohmhaas.com [seaoc(--nospam--at)seaoc.org]
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